Energy Ltd. News #49
Copyright 2012 Craig Carmichael - March 1st, 2012
Feature: 2 Volt Salty Batteries - 3 Major
Advances in a month improve state of the art!
* Perforated Hard Plastic Pocket
Electrodes simplify "DIY" battery making
* Manganese Negative Electrode Works: Green, cheap, high energy, long
life 2 volt cells
* Nickel Manganate Positive Electrode: high conductivity improves
Month In Brief (Summaries)
* Much of the month was spent making the best new chemistry - and new
construction - batteries yet
* I talk on the Turquoise Battery Project and
DIY battery making at Ideawave 2012
* Electric vehicle club meeting(s)
No Project Reports on: Electric
Hubcap system, Weel motor, Sprint car conversion, Electric outboard
from scratch, DSSC solar cells, Pulsejet steel plate cutter, NiMH
Magnetic Impulse Torque Converter Project
* Idea: the magnetic impulse rotors should make enough torque to run
bike as-is, without 2nd mechanical hammer stage. (as an interim
* Adding switches to light fixtures
* Hanging LED wall lights to replace table lamps?
* Turquoise Energy is finally accepted into Energy Star program
* Perforated Plastic Pocket Electrodes:
Evolution of a whole
new "DIY" way of making batteries.
- rigid perforated plastic container encapsulates
- perforated flat plate electrodes (perf. plastic sheets
glued with ribs into thin boxes)
- perforated square cylinder electrodes (perf. plastic
sheets heated & bent into square tubes)
* Problems with negatrode self-discharge solved!
The metal or carbon current
collector, not the chemicals, has been bubbling hydrogen! Must use
zinc or silver
or alloys thereof.
* High energy manganese negatrode works:
renders NiFe, NiCd, NiMH and NiZn obsolete?
* Cells can be alkaline during cycling with KCl salt electrolyte
- no need for caustic KOH. Ca(OH)2 additive can make intermediate
alkalinity for potentially improved characteristics and cycle life.
* Got thinner plastic, .020" styrene -- It wouldn't form into cylinders
* Got .030" PVC plastic -- characteristics seem ideal.
* Nickel manganate: higher positrode
for better performance... or is it a better chemistry? - Nickel
[per]manganate positrodes instead of nickel [oxy]hydroxide
NiMn2O4 -- (NiMn2O4, Positive Electrode Mix, for sale,
20¢/gram either one).
* First working cell with 1/4" square cylinder electrodes, nickel
and manganese (-) charges to about 2.3 volts.
* Ordered laser diodes, to have CNC machine burn the perforations in
the plastic, ideally sized and spaced, automatically. (Too simple!)
Construction Manuals and information:
Electric Hubcap Motor - Turquoise Motor
Controller - 36 Volt Electric
- Nanocrystalline glass to enhance Solar
Cell performance - Ersatz 'powder coating' home process for
- Electric Hubcap Motor Kit
- Sodium Sulfate - Lead-Acid battery longevity/renewal
- NiMH Handy Battery Sticks, Dry Cells
- LED Light Fixtures
...all at: http://www.TurquoiseEnergy.com/
(orders: e-mail email@example.com)
February in Brief
Although the month started with a quick test of the torque
converter (which showed it needed some adjustments to the
developed a strong interest in batteries, partly since I was going to
at Ideawave Conference [ideawave.ca] on the battery project on
25th. It seemed reasonable to put all effort into finally making
working battery cells - to
finally have some at any time
before the talk would be excellent!
First I tried to think of
way to make test electrodes. This rapidly evolved into a whole new
of making electrodes and batteries. I spent the first week developing
it, and ended up with perforated hard plastic pocket electrodes.
I started with .063" ABS I had and tested out the concept. Next, .020"
styrene was too soft, but I ordered some tough .030" PVC and switched
Two pocket electrode layouts were possible: perforated square cylinders
perforated flat plates. The cylinder layout is easier
for DIY construction, requiring only a few simple special tools, and I
decided to adopt this in spite of higher internal resistances. One
special power tool I came up with was a scucum
sewing machine to punch thousands of perforations in the rigid plastic.
that, I couldn't think of a practical way it could be done - almost
even for one electrode. Even at that, the number of holes I'm making
per unit area is less than 1/5th that of electrodes from a commercial
NiFe cell. On the 25th, I had the thought that a CNC laser might also
work better than the sewing machine - and cut out each electrode piece
to exact size as well.
Towards the middle of the month, reading a battery
research paper from Iran at last
twigged my mind into realizing that not only the electrode chemicals
but the current collectors have to have sufficient overvoltage
reaction voltage. Edison used either steel or nickel plating for iron
negatrodes, so I
figured anything would be fine. But iron is a lower voltage electrode.
Here lay all my mysterious trouble with high self discharge of all my
voltage electrodes. Neither
my copper, nickel, stainless steel, graphite nor grafpoxy had a high
enough hydrogen overvoltage, and it was the grills causing the
electrodes to discharge. The simple solution is to use zinc plated
metal. Zinc has the overvoltage. Or silver. An alloy with zinc,
"optalloy" or "white bronze", as presented in the paper, also appears
to work well.
Once I had the overvoltage problem figured out, manganese
for negatrodes at long last worked fine.
It appears to be the best ever: high
voltage, high amp-hours per kilogram, good
conductivity, and (to all appearances) very long cycle life.
"Mn" - fortified by 1% Sb2O3
(or whatever?) to raise its overvoltage - would appear to be the
outstanding choice for future negatrodes, probably
rendering NiFe, NiCd, and NiZn obsolete. The energy density should
or exceed that of lithium ion types for a fraction of the cost.
I came up with a better positrode chemistry as
well: Nickel manganate, NiMn2O4, instead of nickel hydroxide, Ni(OH)2.
I couldn't find this substance to buy it, about which
to be known, so I tried making it from nickel chloride
and potassium permanganate, and got a foul smelling tray of sludge,
which the water
had to be evaporated off of, the house smelling of chlorine or
something for days. Then I made some by
torching Ni(OH)2 + 2 MnO2 powders mixed together with a swirljet
propane torch. The end product had a lower resistance than the first
Nickel manganate has a highly conductive "spinel"
crystalline structure, and it made a more conductive electrode that
This was my original reason for investigating it. I'm not sure of the
exact charging and discharging reactions, but they seem to have the
voltages as with Ni(OH)2. A difference is that they should discharge
right down to valence 2.0, whereas Ni(OH)2 won't conduct current well
once average valence is below 2.25, so they'll probably get more
performance out of
each gram of nickel, which is the only somewhat costly substance
present in any quantity the cell.
years of mixed results at best, a battery with
all the features above worked well the day before my battery making
talk at Ideawave 2012. A Times-Colonist newspaper reporter interviewed
me, and I wrote him a brief description of the battery, leaving out
most of the ad nauseum technical details I always so scrupulously put
in. It probably bears reprinting here (re-edited):
* This potassium chloride salt water electrolyte battery with mildly
chemistry is safer than concentrated acid or alkali.
* The cells are about 2 volts instead of 1.2. It has at least as high
energy density as lithium ion, but the materials are dirt cheap.
* The electrode construction is a new type: square cylinder,
"perforated hard plastic pocket electrodes". The encapsulated chemicals
form a solid "briquette" inside, with a terminal wire sticking out the
Perforating the plastic with a sewing machine or CNC laser cutter makes
the battery "DIY"
* The positive electrode substance is new: nickel manganate. This works
similar to regular nickel electrodes (nickel hydroxide), but it's
insoluble at neutral pH for double voltage, and its low
resistance gives heavy current capacity.
* Uses a new high voltage, high energy manganese negative electrode,
reactions are made possible by an additive of 1% stibnite to stop
Finally, I updated the battery making book on the web site
about three times to try to keep up with the fast paced major
When John McCain was running for president of the USA, he
suggested that $45,000,000 should be given to anyone who could come up
with a better battery for electric cars. At last, I feel sure I'd have
earned that money... if McCain had won the election... and followed
through on it... and probably only if I was a US citizen... Instead,
after the conference I scrounged some firewood from a tree cut down
down the street - Oh boy, heat for next winter!
The Ideawave Conference got local newspaper and TV
coverage. The batteries got a couple of lines with my name in the
paper, and in a breath in "From impromptu poetry to better
batteries..." on the TV news.
Along with the
battery work, I was trying to set up a
netbook computer with a new solid state drive and with Linux. A friend
who was a Linux guru helped. Finally the computer simply refused to
come on just when all was finished and it was finally reassembled with
the new fast and silent "drive". It turned out (just before I was about
to throw it in the garbage) that downloading and installing a new BIOS
per a complex procedure fixed it. Everything took a lot of time that
ate project time. I needed to use the netbook for some jobs and
software, including to create new files for the PCB maker, who couldn't
seem to read the files e-mailed from my Macintosh, and to upload the
newsletters onto my other website with a new program.
Almost the only non-battery R & D I did was to add a
switch to an LED light fixture so it could be easily turned on and off
if it was hung on a wall. There seems to be potential that wall mounted
LED lights could replace many lamps as well as installed light
fixtures, thus saving the table space occupied by the lamp.
I went to a "VEVA" electric vehicles club meeting in
Victoria on the evening of the 15th, the second one and now intended to
be monthly. The instigator arrived on his electric bicycle. There's a
web site: http://veva.ca/veva-islands
Here I found someone who had a good experience buying a
Chevy Volt. No one badgered him and it arrived a couple of months early
instead of late. I got a ride. It was certainly a luxury car - really
quiet, smooth and with every conceivable appointment and more you've
never thought of. Of course I still
say they're making them that way to keep the price, over 40,000$, out
of most peoples' reach, but it's nice you don't get hassled if you go
to buy one. It was said General Electric has ordered 5000 of them -
that can only be good!
The "Seguay" was a no-show. Maybe next month? The "real"
VEVA meeting in Vancouver the same night evidently showed an electric
outboard boat motor made or converted by someone in North Vancouver.
And my friend's i-MiEV did finally arrive this month with
no further arguments or problems. It's a beauty, and if not cheap, it's
at least substantially less costly than the Volt. Perhaps the zeal, or
the grip, of those who want us to stay on oil forever is waning. He
wants to show it at the March
meeting. (Wednesday March 21st at
Dairy Queen, 2350 Douglas Street, Victoria BC - "Driving, Riding,
Testing & fun from 6:30 to 7:30. Meeting at 7pm to 7:30")
When my new chemistry
batteries are being mass produced (whenever that may be), it should
start knocking around $10,000 off the price of electric cars versus
using lithiums. (Boy could I use $10,000 'extra' dollars this year!)
I did get a non-battery idea: to try to get the torque
converter working on the dirt bike,
using the rotors already made or making a similar pair. The bike,
needing less torque than the
car, would only need the magnetic impulse part of the converter, which
seems to work great, and not the second mechanical assist part whose
present construction is more questionable. It seems
like a great interim project to prove out that part of the converter
and note any improvements that might be made to it, in operating
parameters or construction details.
I wanted to rush in and try to get it working by
month's end, before starting on my tax forms in March. But after weeks
of fast paced battery progress, writing an
up to the minute talk about it for Ideawave,
and then actually attending the conference and speaking, there was
hardly a clean dish in the house, the larder was bare, the place was a
mess, and a break could surely only do me good. With only 3 days left
February, the converter would have to wait until later in March. But on
the 29th I bought the
additional parts I
think I'll need - two choices of sprocket gear and some bearings.
On the 29th also, the CNC conversion kit for the milling
machine arrived, and I ordered plastic burning laser diodes to
perforate battery electrodes automatically.
Magnetic Impulse Torque Converter Project
An initial test at the start of the month showed the
springs weren't returning the "hammer rotor" to center, and a quick
adjustment didn't fix it. A couple of bolts were sticking out and
hitting the chain. Then I got into the new chemistry batteries.
Later I had an
idea: I still had the dirt bike here, and with the torque wrench I
measured how much torque it actually took at the motor shaft to move
the bike, on level ground, and with small resistance to motion such as
a bit of uphill grade or a rock. It all seemed to be under 10 foot
pounds - mostly closer to 5 or even less. Since the chain is geared 4
to 1, that equates to 20 to 40 foot-pounds at the wheel. That's 1/3 of
what the car needs. (It would be still less if the wheels weren't
As one might suspect from these figures, plus both the
motor specs (approximate tho they are) and the ride last summer, the
motor draws about 11 or 12 amps per foot-pound, hence the 80 amps it
took to go upslope would have been only 6 or 7 foot-pounds - about 25
at the wheels. As I said
at the time, it was as if the bike was stuck in 3rd gear.
A key difference between the bike and the car is that the
magnetic impulse of the torque converter seems able to put out about 8
or 10 foot-pounds as is, so it wouldn't need an additional 3-4x boost
of a mechanical hammer part to roll the bike. I have the rotors and can
get a fitting sprocket gear locally at Princess Auto, so it would be
easy to rig up the torque converter on the bike, by making a longer
shaft for the motor. With the variable advantage of up to 5 to 1, plus
the 4 to 1 chain advantage, the magnetic part of the torque converter
should do a nice job of running the bike while being very easy on the
motor. In fact, the 4 to 1 ratio might be reduced to 3 to 1 for
higher top speed.
Applied directly to the Tercel car wheel, the converter
would need something like 100 to 150 foot-pounds at its output; to the
Sprint mechanism with reduction, 25 to 40; to the bike, somewhere
between 5 and 15. Doing the bike
shouldn't be a long
project, and it seems like a good one for late March (after the
Turquoise Energy Limited year-end tax return is done) - (a) just to get
something that works after almost three years, and (b) to potentially
from before scaling up to cars.
On the 29th I went out and bought a couple of sprocket
gears, bearings, and a "1/2 link" for the bike chain, which it needed
have had long ago if I'd known there was such a thing. The link even
cotter pin so the chain could easily be attached to and removed from
I got a 12 tooth gear (4.33 to 1), but I also found an
complete with center bearing. If I can drill bolt holes through that, I
can mount the output rotor with the copper wedge on it and things might
be easier to assemble and more compact. It has 17 teeth (it was the
smallest one for #40 chain), so the final drive ratio will be 3 to 1
instead of 4.33 to 1 -- If I use it I hope the torque converter can
somewhat higher than planned load.
LED Lighting Project
What with hanging LED light fixtures
from nails on the
wall and plugging them in and unplugging them, the idea occurred that
it would be nice to have a switch on the light. I had a rare visit from
a cousin, who immediately got the idea that one could replace table
lamps with wall-hanging LED lights, which wouldn't occupy table space.
She seemed quite enthusiastic. I had been sort of figuring this myself,
and by this time had several LED light fixtures on the walls, but I
thought that others might not like the idea. Of course, one could make
them all dim-off-bright "3 way" lights with 3 position switches, too.
The next day I finally got around to putting a switch on
one of the fixtures. I had been concerned that flipping the switch
would cause the light to swivel back and forth, but then I got the idea
to turn the switch sideways, so it goes in and out from the wall. The
standard switch conventions now need an extension... is "off" push
or pull? I made it "pull" because it's easier to push it on groping in
the dark than to pull it.
I also got a shipment of nice plastic 6" globe diffusers,
and a few "plastic jar" diffusers, which are interchangeable with each
other and with the glass ones. I like them better, especially for
shipping if I do mail order.
I finally got acceptance and instructions from Energy
Star, but with all the battery work, and the unco-operative netbook
computer, I didn't get around to even reading it.
Turquoise Battery Project
Shorter Version of long story
A couple of days into February previous battery cell designs went
the wayside: I came up with a
whole simpler way to make batteries: with perforated hard plastic
electrodes. These self contained, self supporting electrodes might
be my best DIY battery making
A problem is that normally everything
has to be precisely fitted and crammed into place as the cell is
closed, or the electrodes swell up and lose their
conductivity when liquid is added. However, the fit of electrodes in
enclosures is of little import - tolerances within the battery can be
quite sloppy and electrode sizes and shapes quite approximate. With
perforated metal electrode enclosures, Edison even used round "pencil"
tube positives and flat plate negatives.
Compacting electrode powders into a
square perforated cylinder
I thought the idea might well be impractical, but I did
some footwork looking for ways and means. The essential DIY perforator
making thousands of tiny holes in rigid plastic sheets turned out to be
a heavy duty
sewing machine. Later, an idea from the Ideawave conference was
that a CNC
laser cutter could do the job better (more dense and better formed
holes) and unattended for 'real' production, and I ordered laser diodes
to mount on my own CNC drill-router - that'll be in fact cheaper than
the used sewing machine was.
Once the sheets are perforated, there seemed to be two
possible layout options: perforated square cylinders, or encapsulated
plates with perforated faces. For a while I was using 1/16" ABS
plastic. 1/2" square cylinders worked but had a disappointingly high
internal resistance, so I made some 1/4". Then I had better success
with a 1/2" one, so the jury's still out which is better.
plastic would be better. When at length I obtained some .020" styrene
curled up in the oven, so it couldn't be formed into cylinders. I
decided it was too soft, period.
ordered some gray .030" PVC near the end of the month. It
turned out to be pretty
stiff, a good hardness. The Singer 503 could punch the holes. So could
the cheap machine, but only barely and slowly. And, it could easily be
formed into a square tube in half a minute just by heating it with a
heat gun - forget the oven. It's the keeper.
cylinders are so much easier to make than the better conducting plates
that I think they're a keeper. (And in what other electrode can
you pull the whole current collector out and replace it?) But so far,
it looks like getting enough current to run an Electric
Hubcap motor would mean having enough battery substance for a very long
driving range. Hopefully this can be improved.
The perforated pocket electrode idea goes back to the
1880s, but the
material is changed from nickel plated steel to rigid ABS, PVC or
First flat plate perforated plastic pocket electrode.
I glued ribs outside on both faces, fearing the center would bulge out
For flooded cells gas needs a gap to bubble up
This nickel plated current collector grill and leed was the last one
before I found out they had to be zinc coated.
With both layouts the essential point is to
hold the electrode substance tightly compacted within the perforated
it can't swell and lose conductivity. The flat plate with grill yielded
substantially lower resistance and higher current capacity.
(not surprising) However, the cylinders seem much simpler to do.
First pocket electrode battery with 1/2" square cylinder electrodes.
Case is sheet ABS fised with methylene chloride.
For experimenting, pocket
electrodes can be immersed, removed and swapped around, so any working
can be used to test multiple opposite experimental electrodes. For
making batteries, as many pocket electrodes as desired can be assembled
of any size.
Before mid-month I
that not only the electrode substance but the current collector
have sufficient overvoltage not to bubble oxygen, chlorine, or hydrogen
gas at the electrode charging voltage. Hydrogen generation by the
negatrode collector grill has been the heretofore mysterious
cause of all my frustration with cells being hard to charge
and having unworkably high self discharge - it had little to
do with the chemistries being tested except that they were mostly
higher voltage, over a volt. The only negatrodes I made that really
worked were one with nickel
at -.5(?) volts... which is below hydrogen's voltage entirely, and a
zinc sheet electrode... with the soldered leed out of the electrolyte.
Finally I know what's going on.
The simple solution seems to be
to plate the negatrode current collector with zinc, or
silver, or an alloy including one of them, which metals have
overvoltage. The copper, nickel, steel, tin,
carbon or grafpoxy collectors
or coatings I tried all only work with lower voltage negatrodes -
cadmium, metal hydride, or iron. Of course, I've mostly been trying to
voltage negatrodes, zinc or manganese, for best energy density.
Zinc coated wire and grill can be purchased at
agricultural supplies, tho the finest grill there was awfully coarse
for a battery. I tried melting zinc (dry cell cases) in a stainless pot
on a stove burner, and it worked. It seemed to be about 1/2 slag,
yellowish zinc oxide, but there was a good pool of zinc too. The ends
wire or grill can be dipped into that to coat them, probably with borax
Zinc plated parts hasn't 100% solved self discharge
problems, but the remnant may likely be explained by impure
electrolyte, impure ingredients, or (tho unlikely) nitrate-nitrite
reactions of the ABS plastic - the manganese is about the same as the
zinc, which ought to stay charged. Or perhaps the zinc plating on the
bolts I used doesn't have 100% coverage? (Yes, this did seem to be the
These two solutions, perforated plastic pocket electrodes
and zinc coated negatrode components, put the project on track for
developments. The manganese negatrodes with 1%
stibnite to raise the hydrogen overvoltage finally started working
principle "NiMn" now looks like the
singular chemistry of choice, probably better for most
applications than NiFe, NiCd, NiZn or NiMH... or PbPb. It has high
and high conductivity without zinc's troublesome zincate ion, the most
energy of all per kilogram, should have exceptionally long cycle life,
green and it's dirt cheap.
I did a bit of testing of harder jewelry carving/casting
waxes to make "graf-waxy" for the positrodes. Resistances were higher
than for "grafpoxy" with the same amount of graphite by weight, but it
got hard to work if I added more graphite powder. I ended up diluting
it with parafin wax,
which is much softer. More experiments will follow.
At the same time as
I conceived the new construction, I got the idea of using nickel
manganate in addition to or in place of nickel hydroxide to improve
conductivity of the positrode. Cell conductivity and hence amp capacity
is substantially improved. A pretty small battery might
start a car.
I made some, and tried replacing the Ni(OH)2 entirely. It
worked. The nickel might charge from NiMn2O4 [II] to, eg, Ni(OH)Mn2O4
[III] and or Ni(O)Mn2O4 [IV], similar to regular nickel oxyhydroxide
reactions. In addition, it'll probably squeeze more out of the somewhat
pricey nickel, discharging it readily almost to valence 2.0, whereas
nickel oxyhydroxide ceases to provide much current when the valence
drops below 2.25 and so it doesn't attain the theoretical amp-hours
values. It was also likely to be solid both charged and discharged in
neutral pH electrolyte. And in neutral pH, the voltage of nickel is
almost a volt instead of half a volt, so altho the molecules weigh
more, the energy density of the nickel itself is doubled, improving the
watt-hours per dollar performance.
I made a bit by converting some nickel oxide to nickel
chloride and then adding potassium permanganate, but it was a smelly
mess and tedious to make a small amount, and it was slow as the liquid
had to be
evaporated off. I made some more by mixing nickel oxide and
torching it to red hot with a swirljet propane torch. (Outside, in
stainless steel pot, with a respirator on.) As long
as it has the 1 to 2 molecular ratio of Ni to Mn, as many oxygens as
want to can attach themselves to the NiMn2Ox, in the flame and then in
Its conductivity was better than the liquid-made batch,
of MnO2 and Ni(OH)2 (which gave no reading at all). As made so
far, it certainly won't replace graphite, but I doubt I've achieved the
possible. Positrodes made late in the month from this and
graphite powder seemed to perform much better than nickel hydroxide
positives. So this substance looks like a keeper!
I also studied the Pourbaix diagrams of the metallic
elements of interest and came to the conclusion that the ideal
pH would be in
the range of 10 to 12.5, neither neutral (7) as I've been trying,
solidly alkaline (14)
as is commonly used. But then I started to realize that
charging reactions turn the cells alkaline, probably to pH 14,
regardless of what's used
for electrolyte, just as lead-acid cells always return to being acid,
pH 1, even after replacing the acid with neutral sodium sulfate.
with KCl salt, however, is safer than using caustic KOH -- the
concentration of caustic OH- ions will remain low.
But once I had this all
worked out, the last cell of the month (with NiMn2O4 & Mn) seemed
to stay pretty neutral, and seemed to work admirably. After adding
Ca(OH)2, it appeared (as far
as the pH test paper could be relied on), that the electrolyte pH was 7
or 8 on the positive
side of the separator paper and about 10 to 12 on the minus. (And
that's without even any special coatings on the separator.) This range
seems just about ideal.
I also found that the pH
test strips I was using, with
distinct colors for each pH, are inaccurate in the alkaline area,
clearly indicating "13" in
concentrated KOH, which is clearly 14. The other type I have is even
worse, the alkaline colors all beng very similar (not to say
indistinguishable) on the chart. I need to find something better
before coming to exact conclusions about alkalinity from test results.
On the 23rd I made a battery with all the features
described above, and on the 24th, charging revealed that it worked -
after 2 out of 3 negatrode leeds corroded off, fortunately leaving just
the good one. That's the end of the "Short Version". The rest of this
newsletter (2/3 of it) is a long,
less a blow-by-blow, day-to-day diary written as I was doing the work.
It's probably worth reading only for historical record or for a few
"how-to" details if you
actually want to make batteries.
Simple Homemade Battery Electrodes? - Evolution of a new design
As I considered all the work to
make each electrode and get it into a battery cell to test it, a
idea for test electrodes came to me on the 3rd, which was a convergence
separate ideas I've had over the last couple of years, none of which
quite had everything that was needed separately. This developed over a
week or so into into a new, easier to do, DIY battery design. The
sections below are pretty much a diary of the project. To cut to the
chase, I suggest skipping to design 4.
Design 1 - simple perf tube test electrodes (was a no-go)
* Take a piece of fat
polyolefin heatshrink tubing [electronics parts
store] and put lots of tiny
holes in it (sewing machine with no thread)
* take a carbon rod from a D cell (no grafpoxying to do)
* put the piece of heatshrink around it, leaving the top clear for a
* tighten a cable tie [electronics parts store, etc] around at the top
end. Now it's a plastic 'pouch'
with the rod in the middle.
* stuff in the powder(s). Tamp it in well with a pipe that just fits
over the carbon rod, and just fits inside the heatshrink. K & S
brass tubes [hobby shop] come in telescoping sizes in 1/32" increments,
so a custom pipe can be made. The better you can cram the powder in
short of ripping the heatshrink, the better the battery should work.
my carbon rods and heatshrink, 3/8" and 13/32". I used a little
plastic 'stick' the first time, but the compaction, and hence
performance, was poor.)
* put a cable tie over the bottom end of the heatshrink - now the
powder is enclosed, a plastic
shelled "pocket electrode"
* take a heat gun to it to shrink the
heatshrink (a half-assed job of further compacting the electrode)
* put two such electrodes into a jar of electrolyte and try them out,
with or without painted separator paper and cellophane doping ideas.
Theoretically they're self insulating, but there may be enough powder
squeezes out the holes to short two together. If that proves to be the
case, use separator paper between them: watercolor paper, coffee filter
If you make a jig with a larger pipe to go around the heatshrink and
hold it upright on the table, you can probably cram the powder in
better with less risk of ripping the plastic, and both hands will be
free to work. If the outside tube is square and the tamper can be made
to fit... say a square piece of steel with a hole drilled for the
carbon rod... the electrodes could pretty much fill the space in the
case, and you could tamp with a hammer. (Say, I'm really starting to
To try a new electrode idea, it would be simple to re-use
the working opposite electrode. It didn't matter that the cells
wouldn't have much current or amp-hours, only whether they basically
worked and held charge. Then it would be seen whether it was worth
doing a proper electrode and battery cell.
The idea seemed promising enough to at least try out. The
obvious choice was to make a zinc electrode, and try it first with
nickel electrodes from the nickel iron cell. The mix was simple:
.2g veegum (bentonite clay)
work without overvoltage raising... but better with it than without.
First I crunched up some stibnite with a hammer on an anvil to make it
as fine as possible, as I had noticed even the 'fine' powder did a lot
of crunching when ground with mortar and pestle - it's too coarse.
Veegum for glue. About
6 grams stuffed into the 'pouch', theoretically about 3-1/2 amp-hours
worth. The nickel electrodes should be of similar capacity.
Electrolyte pH, left over from the Mn electrode, was about
13. The nickel plating on the nickel electrodes showed some
discoloration that might indicate they were starting to corrode in the
lower pH electrolyte. The voltage started at about .45 - the zinc was
entirely discharged as ZnO. I was eager to get it going, but the
Alkaline Storage Batteries book says to leave zinc electrodes in the
KOH for a day before charging, so the alkaline electrolyte can remove
any zinc carbonate. The voltage was rising, and in a few hours it was
around .8, so something did seem to be happening.
If the Pourbaix diagram is correct, at pH 13 instead of 14, the zinc
without making the troublesome zincate ion. How many things have people
tried to eliminate or reduce the effects of this ion, but no one
thought just to lower the pH! On the other hand, the standard dry cell
reaction Zn to ZnCl2 is -1.04 volts in neutral solution, which isn't
the voltage shown on the Pourbaix. So the idea is suggested, but not
proven, by the diagram indicating it.
The zinc electrode was crap. It sort of charged - about
like so many of my poorly performing electrodes. I don't think the
powder was well enough compacted. Later I uncovered two separate
causes: first, the zinc oxide powder was yellowish gray. According to
Wikipedia, that means it's not pure - it should be white. I had another
bag, and this one was white. But I found the resistance was quite high
even when well tamped down. I added graphite to the second attempt.
But by late afternoon of that day
(4th), I had not only ideas of how to improve this construction and
make real batteries with it, but all the vital jigs and parts ready to
go - even some more appropriate sewing machine needles.
Design 2 - "Real" Perf Heatshrink Cylindrical Pocket Electrodes
(second no-go design)
Compacted zinc electrode on carbon rod, and perforated heatshrink.
Note ABS plastic "washers" at each end.
Heatshrink on and shrunk
I replaced the cable ties with 1/8" thick ABS "washers"
that fit tightly around the carbon rod. A brass tube with 1/64" wall
thickness [K & S Brass, hobby shop] defined the outside shape of
the electrode, and the washers fit just inside it. The brass tube fit
upright in a hole in a piece of wood for a holding jig. The heatshrink,
fit just around the brass tube. I used 1/2" heatshrink, and "D" dry
cell carbon rods, which are about 5/16" diameter. I thought "F" cell
would be a nice length, but they're not as common.
I used this same brass tube to melt through the ABS sheet
form the washers, heating the tube with a 1500W heat gun and pressing
plastic until it melted its way through. (Drilling the 5/16" holes for
the carbon rod dead center was a challenge, and there were more rejects
than successes. Another jig or tool was required.)
First the bottom 'washer' was pushed over the bottom of
carbon rod, then the carbon rod was pushed into the bottom of the brass
tube. The top of the rod stuck out of the tube. The tube was held in
the hole in the wood.
A piece of the next size up of telescoping brass rod was
placed over the upright tube, and a little of the electrode mix was
dumped in through a funnel.
This larger tube was pulled off and a pipe (perhaps made
telescoping sizes of brass tube) was inserted into the upright tube. (I
had a lathe and a piece of 1/4" brass NPT pipe. So I turned the outside
bit until it fit well, and turned the end flat. This gave a nice solid
pipe, and the inside hole was a good size.) The pipe was gently but
firmly tapped with a hammer to compact
the particles in the tube. (Being careful of the brittle carbon rod!)
The process of pouring in powder and compacting it was
repeated until there was maybe 3/4" of carbon rod left free at the top.
top washer was slipped on and pushed down.
Now the perforated heatshrink was slipped over the bottom
end of the tube, and the electrode was pushed out of the tube with the
pipe, into the
heatshrink. Then the heatshrink was heated to tighten it over the
Presto! - I thought - one great Plastic Pocket
Well... that was the theory. The mix for the second
electrode, just a day after the first, was 20g calcined zinc oxide
(white - purer), .3g Sb2S3, .4g veegum, 7.5g graphite powder, and 1g
dieselkleen. The graphite powder greatly improved the poor
conductivity... for the initial test. I'm not sure why they didn't use
it in the mix in Alkaline Storage Batteries except that the
metal pocket electrodes were very thin, so all the zinc was very close
to metal. Less than 1/3 of this mix fit in.
It proved unexpectedly difficult to get the electrode to
slide out of the brass tube. I don't know why I didn't think it would
be, after mashing in the zinc mix with a hammer and punch. I could try
putting in a piece of polyethylene to make it slippery. If that didn't
work, I'd have to remake the tools so the heatshrink went inside the
tube with the electrode while it was being compacted. That might
come out easier... and hopefully the heatshrink wouldn't rip
during the hammering.
But I did eventually get the electrode out, then I shrunk
the heatshrink tube around it. Then it went into the battery to sit
overnight. It performed better than the first one... but not well.
nickel-zinc in alkaline solution is a known, working chemie, the
conclusion is the construction is at fault. [Note: It was actually the
low hydrogen overvoltage of the carbon rod.] The main thing that could
go wrong with the construction would probably be, as usual,
compacting or failing to keep the electrode compacted once it's in the
cell. It was supposed to keep itself compacted, but evidently the
heatshrink can expand too easily for this. But the heatshrink is about
the toughest stuff one could punch holes in with a sewing machine.
It seemed as if the whole idea was a failure. How could it
be redeemed? One way would be by finding a material that worked, that
had the strength. But if it didn't shrink, how could it hold the
Design 3 - "jammed-in" square heatshrink electrodes battery (not
There was another
way: make the electrodes square, and
make battery cases that were an exact fit, with no
room to expand except by bulging the slightly flexible ABS sides. A
square cross section electrode would be better
anyway - less liquid and
better conductivity in the battery.
Electrodes would be placed
checkerboard style. Each electrode has its post sticking up through the
the battery, and all connections are made externally, with metal clamps
on the exposed top section of each carbon rod.
It would need square
tubes and jigs. Doable, but the jigs would take more doing. It would be
better and easier to have rigid plastic tubes, and to compact the
electrodes within the actual tube. Where could I get square ABS tubes,
and how could they be perforated?
At this point, the idea had
moved away from a simple way
to make test electrodes, to another full-fledged battery design. But it
seemed like a good one - instead of two flat electrodes defining the
size and shape of a small cell, a checkerboard of any number of
electrodes could be accommodated to make a battery cell of any desired
size and capacity. It made sense.
Then, perhaps the terminal should then be a grafpoxied fat
copper wire, with the top end bare for the external connection? That
had the disadvantage of being thinner with less surface area to
interface to the electrode substance, but the advantage of eliminating
the arbitrary height constraint imposed by the D cell carbon rods.
Taller, thinner electrodes would be the result. If they were, say 10mm
square by 6cm tall, each one would have about 1/2 the capacity of the
flat electrode design. So a cell with 16 of them, just 2" square by 3"
tall, would have four times the capacity of the flat "cassette tape"
size battery. I decided to try common #14 AWG house wire and see how
that held out during assembly, ie, whether it would flex and crack the
grafpoxy. If it did, I'd go to #12 or #10, tho such fat wires would
surely not be required by the currents. I also thought I'd try dipping
the wire in graphite when the epoxy was still tacky. The powder that
only sort-of glued on would give the wire a matt conductive outer skin
which might connect better with the surrounding electrode mix.
It also needed square tubes for the jig, sized to match
some common heatshrink tube size. Optimally, one could use rigid
perforated plastic square tubes. I fear these would need elaborate
equipment to make.
Design 4 - Perforated ABS
Plastic Square Cylinder Pocket Cells (a go, after a couple of
A rigid but thin-walled perforated plastic tube would hold
the electrode compacted.
The only special compaction tool would be a punch with the hole for the
carbon rod. But perforations?... I could imagine setting up
the CNC drill-router and leaving it to drill tiny holes for hours, but
the drill bits would probably break before it got very far.
But at this point, I had another idea, in lieu of such
square plastic tubes and such perforating equipment. My sewing machine
couldn't punch through, eg, the 1/16" ABS plastic sheet - but maybe
was a more "industrial" one that could, if armed with a heavy punching
needle? (And if there was any thinner ABS to be had, that would be an
asset.) ABS can be glued! If one could perforate a flat sheet of ABS,
many options would be open, such as sheet electrodes of any size with
posts glued from top to bottom, at the ends and then about every
10 or 15mm, to form a series of narrow vertical column electrodes, eg,
6mm x 15mm cross section. This would be rather similar in form to metal
pocket electrodes, with the top and bottom also glued shut. Each slot
would only be able to expand to the extent of bulging the plastic a
bit. A grafpoxied wire would stick up from each
slot for external connection.
The ideas flowed fast and furious... perhaps my CNC
drill-router could be armed instead with that leather punch needle? It
would be awfully slow, but it might - probably - work. Maybe it could
hold several needles at once?
One could perhaps take thin wall round tube, heat it in
the oven, and form it square, but the punch has to fit through,
tightly, which would be close tolerance, hard to get with forming. It's
probably easier to glue flat sheets. So it now seemed to boil down to
material I could find: suitable square plastic tube, thinner ABS sheet,
or the 1/16" ABS sheet that I already had.
A couple of hours on the web searching for square plastic
tube yielded no better results than when I'd searched before (looking
somewhat larger sizes for battery cases).
Another idea... one could heat 1/16" perforated flat
in the oven, and try and form them square, around the square punch to
fourth corner would need gluing - and might break open. I decided to
try this anyway, with an unperforated sheet. I set the oven to
325ºF for 15 minutes. I put the 1/2" square punch in too, so it
wouldn't quickly cool and harden the plastic. (I soon stopped heating
the bar, and turned the oven up to 350ºF for about 5 minutes
for each piece - they shrink less with a shorter heating period.)
The plastic shrank in the oven (and thickened, perhaps
proportionately) and only covered 3 sides of the square. But it looked
Promising. It seemed to have the strength to hold an electrode together
without much swelling.
Then I had the
thought that one could lap the plastic over
at the seam. That would be stronger, and even a doubled side would have
less excess plastic than flat sheets with 3/16" or 1/4" dividers glued
in. I cut a bigger piece, 3-1/4"
to go around the
1/2" square with (I hoped) a lap. Then I cut a channel from a piece of
steel. I pushed the soft plastic into the channel with the square bar.
This did a neater job, but the channel was a bit wide and the sides
were rounded. For the next try, I cut a custom channel in a piece of
dogwood. The fit was good, and having the bar inside while forming the
tube ensured it
couldn't end up undersize.
Thus the results were quite satisfactory. The lap meant it
didn't matter whether the edges were square, which of course they
couldn't be with uneven shrinkage in the oven. The finished ends could
be cut or
sanded square. I could already see ways to improve the bending tools
for more even bends at all corners. And ABS comes in black (for
negatrodes) and white (positrodes). But fine tuning could come later -
the main objective was attained.
question then was whether it would be
practical to punch the multitude of tiny holes - preferably in the flat
sheet before forming it into a tube - assuming they wouldn't close up
when heated. If that could be done, it looked like I could soon have
real, working electrodes... followed by real, working batteries. Better
chemistry was merely a bonus!
When I went there, the sewing machine shops claimed
probably no sewing machine could
do it. I started getting discouraged, and thinking I'd have to build a
whole complex machine for the job. But the answer, suggested by the
owner of Victoria Clay Arts pottery supply store, did turn out to be to
get an "industrial" or upholstery sewing machine. He said he had worked
with such machines doing upholstery in the past and they went through
several layers of tough stuff. He said to stop by Tommy's Auto
Upholstery. A worker there demonstrated
that his heavy sewing machine could punch the plastic easily - so much
for the 'expertise' of the sewing machine shops!
I found a
heavier household machine that was just adequate on UsedVictoria.com
The holes were very tiny, much smaller than those of the upholstery
machine. In fact, they pretty much closed right up again when the
plastic was heated in the oven. Obviously he had bigger needles. I was
using leather punching needles. I went back the next day (7th) to see
what type he had - and if they'd fit my machine.
They were upholstery needles, and wouldn't fit a domestic
went back to a sewing machine store to see what else might be
available. There were a couple of slightly fatter needles. I bought the
largest and found my machine wouldn't push them through. I looked again
at my leather punching needles package and found it was an
"assortment". I had
been using the smaller sizes. I took the largest, ("100/16" - 1.00mm
diameter) sharpened it on a
diamond wheel, and tried it. The holes stayed open after forming - it
wires turned out to be an unexpected issue: the first batch had too
high a contact resistance. It was one
thing to make a grafpoxy coated grill with a lot of fine surface area
to connect to, but another to use a single wire with a limited surface.
In the first test electrode, I pulled out the wire with pliers, and
pounded in a fat piece of bare #8 nickel-brass wire to replace it.
it was a negative electrode and being tested in alkaline electrolyte, I
could get away with bare wire.
For the second batch, I added enough graphite to make the
mix 7 to 5 by weight. Then I had to add about 15-20% toluene to make
iit thin enough to work with. And I made a few from a larger gauge of
wire, #10, just for its greater surface area. The resistance dropped
from low kilohms to mid tens of ohms.
To get lower might take carbon rods from dry cells. That
would be a last
resort, but it would guarantee the design was viable if the grafpoxied
wires just didn't work out. It's also possible for negative electrodes
that bare wire would suffice, depending on alkalinity.
Some effective dimensions:
Changhong nickel plated steel pocket electrode (NPSPE): 2 x 55 x 65 mm
= 7.15 cc
Perforated plastic pocket electrode (PPPE): 12 x 12 x 50 mm (inside) =
My original flat electrodes: 4mm x 1.5" x 3" = 11.6 cc (just 1.6 * more
than a single pocket electrode)
max distance material to conductor:
NPSPE: 1 mm
PPPE: ~6 mm
Admittedly the steel pocket electrode should have a much better current
rate than the plastic. But nickel-iron has a slow rate - the iron is at
fault. Nickel-zinc and nickel-hydride are substantially better, but the
nickel is also slow. I think nickel manganate, with either zinc or
manganese negatrodes, will make up the difference; hopefully more. If
not... add more graphite. This is DIY, after all - "good enough and
doable" is better than "ultimate but too hard"!
I've already found that it's pretty much impossible to put
a grill inside an electrode like this - it just gets munched up during
compaction. Another rather appealing option would be to have four
grafpoxied wires, one in each corner, but examined carefully that's
a small improvement. Electrically better but not quite as easy
physically: four wires, about half way from the center to each corner.
This would cut the maximum distance to about 3mm, and four times as
much of the material would be within 1mm of a wire.
The single wire is certainly simplest, and extra graphite
powder probably weighs less than extra copper wires.
For the first electrode I used up the rest of the zinc
oxide mixed for the second heatshrink attempt. Even with the bare wire,
it proved unexpectedly slow, even for being a very thick electrode. I
could have added more graphite to the zinc - would that have done it?
Why did it need any at all? I poured out the electrolyte (still reading
pH 13 instead of 14, but the water looked clear - no more purple color)
and put in fresh KOH and a bit of KMnO4. The water turned green -
manganate, Mn2O4! That would probably turn purple again on charging.
The fresh electrolyte did seem to make some difference,
but not the difference. 100 times better conductivity would
have suited me fine. Would it get better as it charged the ZnO to Zn
metal? Only if enough current would go in to charge it!
Hmm... this time, the mix was well compacted, and could
hardly have swelled much trapped within the ABS enclosure. The
replacement bare wire was a good short circuit. Although it hadn't been
compacted with the electrode, it had taken a bit of force to pound it
in. What then was the problem?
Finally I decided it was a combination of everything.
First there weren't enough tiny
holes - the electrolyte ions have too hard a time getting in and
out. The commercial iron pocket
electrodes have much denser hole spacing, and the metal is thin, maybe
.01 to .015". The plastic is .063" thick, and the fewer holes tend to
close up considerably - around the needle, and more when the plastic is
heated. (This was soon improved with a fatter needle.)
The second aspect
to this is that a 12mm
electrode is really thick, regardless of holes, the
ions have a long way to go.
The third main thing is the distance the electrons have to
travel through semiconducting stuff before they reach the wire. 6mm,
with more and more of the substance as distance increases, is a
long way compared to 1.5mm max for a grill 1/2 way through a 3mm thick
electrode, making the resistance high.
I decided to try the manganese flat electrode with a
nickel coated copper grill made earlier, and encase it as a pocket
electrode with perforated front and back faces. I punched quite a lot
of holes, and since I wasn't heating the flat plastic, they wouldn't
tend to close up in the oven. The difference was immediately apparent:
when a 100mA charge was connected, the voltage only rose 50mV, making
total internal resistance .5Ω instead of several ohms. Presumably - and
hopefully - that would drop as the electrode charged. (How many time
have I expected that and got nothing?)
The cell with this electrode had the usual high self
discharge. It worked great with the Mn(OH)2 to Mn2O3 reaction at -.25
volts (cell total ~.75 volts), and discharged fine at over 100mA for
18 hours - well over 2 amp hours of juice. (It would thus have been
over 4 AH, and of course over a volt higher, with the right reaction.)
But was the tube idea dead? I decided to try making many
in another, thinner, tube electrode, 3/8" square, still with the 1/16"
ABS, and see what
improvement there was. If the first ones had a zillion holes, the next
sheet had 5-8 zillion. I found I couldn't set the machine to do them
too finely spaced, or each one pushed the last one closed. But I could
suck and blow air through it much more easily than previous attempts.
So the next electrode had lots of holes, and it was formed
around a 3/8" square steel rod instead of 1/2" - 9.5mm square instead
of 12.7. This should hit the problem from all angles. It would also
take almost twice as many such electrodes to make a battery cell of a
Then I remembered I'd have to drill a long hole through a
3/8" steel punch, and decided to try 1/2" again but with the more,
holes -- and with a zinc coated leed, the need for which had just been
recognized. I decided to try manganese again, and I used a zinc finish
machine screw, #10-24 x 4" long. Instead of compacting around the bolt,
I compacted without it and glued the bottom on. I got in about 18 grams
of the mix, which would have included at least 12g of MnO2,
theoretically 7 or 8 amp-hours worth. Then I pounded the bolt in with a
hammer. The plastic split open towards the bottom - maybe that wasn't
the best idea - but it might work with a zinced nail! I
patched it by gluing in little bits of plastic.
Initially it looked like the resistance was 3 or 4 ohms.
The simplest DIY fix might just be to put in lots of electrodes in
parallel. 6 * 6 electrodes, 18 of each in a checkerboard pattern, would
bring it closer to .15 Ω.
That would also be well over 100 amp-hours and, at 2 volts, 200
watt-hours. It would take a lot of cells to get to 150 amps capacity at
36 volts, like, 15 in parallel * 18 in series = 270 (almost 10,000
electrodes to make - ouch!), but at that point, it might be around
50,000 KWH. That's over twice what most well batteried EV's have.
Then I made a complete cell. For the positive (the usual
nickel oxyhydroxide, from monel) I used a grafpoxied wire. The
conductivity was awful. The grafpoxy had low enough resistance for a
grill will a lot of surface area to conduct through, but not enough for
a single wire through a cylinder.
One alternative would be to use carbon rods - only F cell
rods (from lantern batteries) were long enough.
The other was to hope the nickel manganate could be used
in place of the graphite, "nimanga-poxy", and had substantially better
conductivity. After all, it was originally for the reputed high
conductivity that I was making the nickel manganate.
If the square pockets are to be used to make cells,
the conductivity was now the thing to focus on. It appeared to be the
last major problem. Trying to compact around a conductive grill
in the cylinder would be problematic. More graphite could help to an
extent, but it's probably not enough. The thinner plastic, when it
arrived, would put the electrodes .086" closer together.
After thinking about a few ideas, I started to realize that 1/2" square
is probably just too fat. It's 6mm from the wire to the corners, where
other alkaline electrodes are 1mm or less from any point to a current
collector. 1/4" square electrodes would have four electrodes where one
1/2" one is. And they would be only 3mm to the corners (2mm with a fat
center conductor), and there'd be 4 wires in place of one. That's a
pretty small size to fill by hand, but undoubtedly more in line with
the electrochemical requirements. The big challenge then is to find
ways and means to make it very fast and easy to make each individual
small electrode. (How do those cigarette roller/stuffer things work?)
I bought 1/4" and 5/16" square steel rod to try. I decided
to go with 1/4" first - given the results with the 1/2" size, the
higher the conductivity gain the better. I made a channel to fold the
plastic into, and then, after perforating and forming four electrode
tubes, made a jig where the electrode fits in sideways, the powder is
dumped or brushed into a slot, and the 1/4" square punch pushes the
powder across the slot and into the electrode. Then it can be tamped to
I ground down the end of the 1/4" square rod a bit so that
it fit easily into the electrode pocket formed around the full
The very next day I inquired about my order and got the
plastic - the store hadn't ordered it for me because it was in stock
all along. Having just made the jigs for the .063" and not even
finished an electrode, I now made new ones for the .020". This turned
into a disappointment as the thin plastic curled up in the oven and
couldn't be made into cylinders. Later I decided it was too soft anyway
- not much better than the heatshrink - and ordered a sheet of .030"
When this arrived on the 23rd, I made 8 electrode
cylinders successfully with it. It perforated okay, was tough (much
tougher than the styrene), and it could be formed after simply heating
it with a heat gun for 20 or 30 seconds.
The electrodes and the cell as a whole seemed to work
acceptably, but the methylene chloride didn't glue the PVC and
conductivity dropped overnight - the electrodes probably swelled up by
spreading the unglued seams. (PVC probably needs MEK for glue.) The
story is continued under the "Nickel Manganate" subheading below, as
the postrodes used that substance.
To recap then, the idea morfed from a quick way to
test electrode into a new and evidently superior (at least for DIY
construction) way to make batteries. There were were
significant challenges and concepts to making
this construction work. At first glance, it seemed it
would be too difficult, as the materials didn't seem to be available.
The conductivity of the positive electrodes still needs work, but it
would seem to be achievable:
a. Using rigid, glueable, and non-brittle plastic for the
outside, and making square electrodes. The overlapped seam also was an
important idea. Square
.063" ABS (acrylonitrile butadiene styrene - the rubbery butyl is what
it a bit soft) or the .030" PVC both flex just enough not to crack
pounding and pressure,
which acrylic plastic or molded epoxy would probably do. And they are
rigid enough to hold the electrode compacted in a square, which the
heatshrink and the softer styrene wouldn't do. Square
electrodes also occupy most of the space in the cell, where round ones
waste space with the weight of extra water filling it. (Obviously, the
.030" saves considerable space over the .063", too.)
b. Forming square ABS or PVC plastic tubes in the oven or with a heat
gun. I couldn't find even
close to suitable square plastic tubes for sale. But I found out a
months ago that ABS plastic went quite limp if heated hot enough in an
oven (eg, 325-350ºF, hotter than I'd been trying previously),
it to be easily formed. (Even if I had found square tubes, they
easily have been perforated.) I made a little jig and formed some tubes
to prove the concept. On the second one it occurred to me to leave
extra material and overlap the join, solving the problem of getting a
solid join that wouldn't be prone to breaking open with the necessary
pounding. The overlapped join
is glued with methylene chloride when the bottom square is also glued
in. The fact that one side sticks out
farther than it otherwise needs to is a small price to pay for simple
c. Using a wire as a terminal and current collector - a simple
zinc coated nail or threaded rod for the negatrode, and a grafpoxy or
nickel-manganate-epoxy wire for the positive. This is simple, better
and easier to
connect to than the carbon rods used in the first couple of tests.
Probably the positives will put together the idea of grafpoxy with
lower resistance nickel manganate replacing [some of] the graphite. The
and working with a single wire and ending up with no gaps in
the epoxy coating are excellent - unlike for a whole brittle grill
with attached terminal wire.
d. How to perforate the plastic was the
last big puzzle. If I couldn't figure out a way, everything else was in
vain. Hundreds or thousands of tiny holes had to be easy to make -
with a drill and a tiny drill bit would have been impractical, almost
even for one electrode. Perforating the heatshrink tube was easy with a
sewing machine, but it would hardly dent the ABS. As related above, I
did get a machine and needle combo that worked, if only just. (Singer
503, 100/16 leather needle, sharpened.) The .030" PVC plastic was
easier, and the cheap sewing machine would - just - go through it too.
Bigger upholstery sewing
machines are available.
CNC Laser Cutter to cut and perforate electrode plastic shells?
At Ideawave, "Victoria
Makerspace" showed (in a photo) their CNC laser cutter, and I got the
idea that the
plastic might be perforated with such a machine, as well as cut to
exact size. That could perhaps make well sized, more closely and evenly
spaced holes - better product than the sewing machine... and do it
unattended, which would be fabulous. The main production question would
probably be not whether, but how fast, it could do them.
The main other practicality
question would be whether it was affordable. I saw a "make a 50 $ laser
the web, using stepper motors from 2 old flatbed scanners, but I'm not
sure I'm into it. Laser safety issues were raised in a number of the
On the other hand, I already have the CNC drill/router and
(CNC to be) milling machine - an appropriate laser mounted on either
one of them would cut. So, what is an appropriate laser, and how much
does it cost? The one in the article was only enough for cutting black
paper, not rigid .030" gray plastic. A commenter suggested 1 to 2 watts
for 1/8" plastic.
On the 29th I found various laser diodes on e-bay. (where
a search for them just the day before had returned "no results"!) I bid
on a pair of one watt infra-red ones that looked about right and got
them for 31
$. It even showed a couple of holes the
seller had burned in gray plastic with one. It could simply be held in
the drill chuck, and could be powered and switched (I'm sure) in place
of the compressed air valve solenoid.
Negatrode zinc plated current
collector coating eliminates [most of
discharge problems - other causes of self discharge
I read about an alloy of CuSnZn 55:25:20% called
'white bronze' that "behaves as a noble metal" and might not corrode. I
thought this might be worth checking out as a better conducting
alternative to grafpoxying wires and grills, but it turned out it
only used in zinc negative sides. There it didn't corrode, but the
paper mentioned it had a
overvoltage than other metals. (Graphite was chosen for the positives,
as I have done.)
statements of the composition of white bronze or optalloy were:
composition: 55% Cu; 25-30% Sn; 15-20% Zn
Alloy Composition: Copper 54 to 65%,
Tin 25 to 40%,
Zinc 6 to 10%
It still sounded potentially useful for reducing hydrogen
generation... Then I began to realize that my problem with all my
higher voltage negative electrodes bubbling was probably exactly that:
the current collector had a lower hydrogen overvoltage than the voltage
of the active chemical. It's probably been the current collectors that
have been bubbling all along, rather than the electrode chemical!
After all, what were my two most successful cells? The
vanadium-nickel cell, and the nickel-zinc cell with the zinc metal
sheet. Nickel as an alkaline negative is only -.72 volts -- lower than
hydrogen voltage (-.833) regardless of overvoltage raising additives.
The zinc sheet had no other metal in contact with the electrolyte: the
soldered connection wire was on the top corner, and the corner was bent
up to be out of the electrolyte. When I replaced the zinc sheet with a
"real" zinc powder compressed electrode, the self discharge started
happening as usual.
I looked again at zinc electrodes in Alkaline Storage
Batteries. Sure enough, where Edison used iron, nickel or anything
for iron electrodes (-.93 volts and they bubble hydrogen easily), for
zinc electrodes zinc or silver metal was used, with a welded silver
leed wire. If the reason had been given, I'd have had this figured out
long ago. (Instead I thought it had to do with them being silver-zinc
Making the alloy could perhaps consist of melting brass
and adding tin to it. (One can melt tin on the kitchen stove and
gradually melt brass into it. This would only work until the alloy had
enough copper that its melting temperature reached the stove
temperature, then it would solidify or at least stop melting more
brass. I wonder what percentage of copper that would occur at?)
Another thought would be to solder a brass wire with tin
flick off as much of the tin as possible, then heat it with a torch, to
get a 'white bronzeish' surface alloy - the surface is what counts.
I found an interesting article on stovetop zinc-aluminum
which may come in handy for such things as this: www.gizmology.net/stovetop.htm
On the 12th, I took some tin-silver solder and a small sheet of zinc
(from a dry cell) and melted some zinc into the solder with a soldering
iron with an 800 degree tip, so presumably I had tin-zinc solder (the
silver is at most only ~3% of the tin). I estimate it had at least 10%
zinc, possibly 20% or more. Zinc should have the best overvoltage. Tin
alone (as shown in the Iranian research paper) was crap.
I worked this along a copper wire with some plumbing flux
until it was completely coated. The wire would be the current collector
for the second zinc square cylinder electrode, which would have more,
bigger holes than the first one, which would show how much difference
improved electrolyte access made. The single job with the paste flux
ruined my good soldering iron tip!
Then I decided there might not be enough zinc in it, so I
decided to melt some zinc in a pot on the stovetop and dipped the wire
in it - galvanize it. I also considered that, assuming the manganese
worked, its voltage was higher than that of zinc, so a pure zinc
coating shouldn't corrode as long as the battery wasn't almost
completely drained. Then I realized I could just buy long thin
galvanized or zinc coated bolts - or even galvanized nails. Say,
something that would actually be easy, off the shelf, for a
I made a 1/2" square cylinder manganese negatrode with a
zinc bolt for the current collector and stuffed it into the nickel-iron
cell with a couple of nickelpositrode plates. The main problem seemed
to be solved, but it still had discharge, which got gradually worse.
Finally I took it apart. The corner had burst from excessive
compacting, and I had wrapped it up with (insulated) wire. I now
wrapped a separator paper around it. That seemed to mostly solve the
it would seem enough manganese and graphite had come out that it had
started touching the nickel plated positrode, something of a short
There's other reasons for self discharge, of course. I
"Impurities in the electrolyte, usually
out of the positive electrode, can be a significant source of
The most important of these is nitrate, which
participates in a nitrate-nitrite shuttle mechanism between the
negative electrodes that can produce very high
self-discharge rates in cells whose positive has not been carefully
Evidently the nitrate-nitrite shuttle can
a cell fairly quickly. It was originally identified when using
polyamide as a separator material caused the problem.
One advantage of flooded cells is that the electrolyte can
be changed if it's causing a problem -- and if it's recognized that it
could be the source of the problem, and that changing it could fix it.
And, of course, if the new electrolyte is purer than the
old... say, could my 50 pound bag of fertilizer grade KOH (it was all I
could get) possibly be less than pure? What farmer would care if his
0-53-0 fertilizer was 2-50-1 with a bit of nitrate? I bet that accounts
for the last remnant of the self discharge! So, that's enough of using
the positrodes in the old NiFe cell and that nasty KOH electrolyte -
I'll have to go with everything new and the "USP pure" KCl salt from
the drug store from now on.
But I'm not wholly convinced... another possibility is
just that the zinc plating on the bolts I used isn't 100% coverage. If
any little spots are unplated or if any plating got scraped off as I
pounded or screwed them in, well, 2% unplated means at least 2%
remaining self-discharge. Come to think of it, those bolts were both
used once. It's entirely possible that tighening nuts on them would
scrape off some of the coating. I got some zinc coated wire at Borden
Mercantile (agricultural supply store) and will try using that - and
plating the ends of the wire too, by dipping them with borax flux into
molten zinc on the stove.
Or, silver also works. A few years ago I made some 88-10-2
tin-silver-copper solder. To digress a bit, I was trying to make a
stronger soft solder, but it doesn't work. I saw there's some with
bismuth that was considerably stronger (3x?), but I can't remember the
other metal, and it was still way below the strength of hard solder.
I found the two batches I made, but they both say 4.7%
silver, so evidently I neglected to re-label the strengthened batch.
I'll take a guess. 4.7% silver might be enough anyway, tho tin alone
doesn't work. I also have some tin-indium solder (low melting point)...
I wonder if that would work? Or tin-lead? (Wouldn't it be just too
simple if ordinary solder works!?!)
I got some purple carving wax - much harder than parafin wax and
"sticky" when hot - on the 22nd, and tried melting it and
mixing it with graphite.
8g wax, 8g graphite: workable, sticky, hard to scrape off, but x10000's
8g wax, 12g graphite: thicker and harder to work with, less sticky,
around 4000 Ω
8g wax, 16g graphite: thick, hard to work with, and flaked off the
copper wire easily, x100's of Ω
8g wax, 2g parafin wax, 16g graphite: thinner and easier to work with,
x100's of ohms.
(Quantities shown don't consider the amounts lost in coating each test
The grafpoxy at 1g to 1g has lower resistance, eg under
200 Ω, and is workable, so so far it appears to be the choice. Of
course, the resistance measured is contact resistance with the
meter probe. The electrode contacts closely all over the wire, so
there's a lot of resistances in parallel for a (hopefully) very low
overall resistance. It might be worth trying out the fourth wire and
seeing what change it has on the internal resistance of a cell overall.
Thinner wax is more workable and a thinner coating should have lower
resistance, but I wouldn't try thinning hot wax with a
flammable solvent. Mixing in parafin wax seemed to work well.
I also got "dap wax", which is brittle but feels as hard
as plastic. Also sticky when hot, it's used to "glue" rocks, etc, onto
"dap sticks" to work with the rock without getting your hands too close
to the machinery. I have yet to try it.
"Grafwax" does work,
and unlike grafpoxy, which is useless
once it's set, wax can be melted over and over again whenever it's
needed. I'll be running more
experiments to see if really good
conductivity, hardness and coating characteristics can be obtained from
any type or mix of wax.
Another Better Chemistry - or a conductivity additive? - Nickel
With MnO2 and NiOOH mixtures both being common in alkaline
batteries, I started to wonder about complexes of these chemicals. One
be formed was nickel manganate or permanganate.
On the web I gleaned
that nickel manganate has low resistivity, owing to its 'spinel
structure', and might be interesting just for that reason. Some of that
in the nickel electrode could make for
higher currents than simple NiOOH.
I say info "gleaned" because there seems to be little of
it on these
substances, at least on the web. They aren't even mentioned in
"Nickel manganate spinels NiMn2O4 are of special interest
due to their low resistivity" -- This was my initial interest.
"Nickel manganate was obtained by precipitation using solutions
of sodium manganate and nickel chloride."
"of nickel manganate NiMn2O4 obtained from nickel permanganate
precursor" -- this was the most promising sounding prospect
(evidently this reaction is "adabiatic", that is, there's no heating or
cooling effect going from nickel permanganate to nickel manganate or
"All permanganates except silver permanganate are soluble in water."
(This is an interesting statement as common potassium permanganate is
only very slightly soluble. I suspect the same may be true of the
"Ni(MnO4)2→ [NiMn2] + 1.502" (If that
last, unexplained, figure is a
reaction voltage, that'd be some cell: +1.502 from the positrode and
-1.56 from a manganese negative is 3.08 volts! However, that reaction
was for thermal decomposition. I'm reading about +.65 from the
pourbaix showing Mn2O4.)
The simple way to get there might be to put some nickel
chloride in the electrode along with the KMnO4, expecting it to become
Ni(MnO4)2 'precursor'... and hope for the best. Nickel chloride should
be easy enough to make: NiO + 2 HCl -> NiCl2
Then in the electrode we'd have:
NiCl2 + 2 KMnO4 -> Ni(MnO4)2 + 2 KCl (all soluble except _probably_
the nickel permanganate)
The first is the desired product, the second is just more
KCl electrolyte. The next step is more suspect:
Ni(MnO4)2 -> NiMn2O4 + 2 O2
If the reaction happened as part of cell discharge,
balanced by the negatrode, it
Ni(MnO4)2 + 4 H2O + 8 e- -> NiMn2O4 + 8 OH-
If it works this way, and if the reaction is reversible
and a good voltage, this is suddenly very exciting electrochemistry:
are three metal cations per molecule, but each reaction creates eight
ions and moves eight electrons, instead of one. That would give
amp-hours per kilogram than the usual nickel reaction, and using 1/3 of
the nickel (hence lower cost - manganese is cheap). It would be on a
par with the perchlorate idea that I didn't get going, potentially
yielding cells of well over 200 watt-hours per kilogram.
Referring to the Mn Pourbaix diagram, it appears that the manganate ion
will only form at pH 13 or above, but at about +.65 volts, which is 30%
higher energy than the .5 volts of the NiOOH reaction on top of the
higher amp-hours, and probably higher maximum amps capacity owing to
lower internal resistance with the manganate spinel structure.
But the Pourbaix diagrams are for non-complexing
chemistries. It may be that nickel manganate and or permanganate are
solid (insoluble), perhaps forming at a somewhat lower pH, and a
different voltage if so - maybe .7 to .8, which sounds ideal if it
doesn't just make oxygen gas on charging.
On the other hand, the reaction
voltage of nickel is lower (both in alkaline and salty solution), so
the nickel might just attach an OH- to
charge to valence 3:
NiMn2O4 + OH- <=> Ni(OH)Mn2O4 + e- [+.95
V at neutral pH; +.49 V in alkali].
consideration, this or something akin seems more
main differences then would be the high conductivity of nickel
compared to nickel hydroxide, allowing higher current flow, and that
nickel manganate and the charged coumpounds are (seem to be) insoluble
at neutral pH where the reaction voltage is around +.95, rather than
the usual +.5 in alkali.
More subtly, the nickel would retain its conductivity
until it was completely charged and discharged, so the valence would go
from 2.0 to 3.0 instead of only from about 2.25 to 3.0, a 33% increase
in energy. Then, as is common in the presence of manganese
compounds, there's the
likelihood that the nickel will
charge to mixed valence between 3 and 4. The second step might be along
the lines of:
Ni(OH)Mn2O4 + OH- <=> Ni(O)Mn2O4 + HOH + e- .
In practice again, this usually goes from 2.25 to around
3.5 or 3.75 with nickel hydroxide, and again this should work right
down to 2.0 with the manganate, so 2.0-3.75 versus 2.25-3.75 gives 16%
more energy. If this is what happens, it would be headed for squeezing
.5 AH/g and 500 WH/Kg from the nickel in salty electrolyte, but
the nickel is more
Calculating with the atomic weights of the substances,
NiMn2O4 ~= 232.5; Ni(OH)2 ~=93; MnO2 ~= 87:
NiMn2O4: 116 AH/Kg, * .95 v = 110 WH/Kg (charging from valence 2 to 3)
NiMn2O4: 173 AH/Kg, * .95 v = 165 WH/Kg (valence 2 to 3.75)
Ni(OH)2: 217 AH/Kg, * .5 v = 108 WH/Kg (charging from valence 2.25 to 3)
Ni(OH)2 + 40% MnO2 additive: 260 AH/Kg, * .5 v = 130 WH/Kg (valence
2.25 to 3.75)
it appears that the energy density from the electrode as a whole would
be fairly similar for either case, probably with some advantage to the
manganate. There are two wild cards:
* if the actual valences that can be attained on charge and discharge
* the amount of conductivity additive required.
As to the conductivity additive, the high resistance
hydroxide often has pricey cobalt oxide added (reducing watt-hours per
dollar). It's also very 'fluffy' stuff, perhaps occupying more volume
than the manganate. So it surely needs more graphite or whatever
is used, diluting down the density more than for the lower resistance
manganate, which might make a more dense and hence physically smaller
electrode. Smaller means less supporting case and electrode materials.
(It's the negative electrode that brings up the battery's
overall energy density: Mn metal has 976 AH/Kg, and thus 1152 WH/Kg at
So much for
theories. With so little known
(at least by me - and no info on
Wikipedia) about the substances and the reactions, it would
have to be 'try it and see', and hope my
interpretations of the results bear some relation to reality. A
positive result would [did] atone for much 'wasted' experimenting time.
The hydrochloric acid with the nickel oxide in it soon had
a nasty smell. I opened the windows and wished I had a fume hood. I
couldn't find my face shield and with safety glasses on I couldn't put
on the fume respirator, so I left the lab. Visiting briefly by holding
my breath, I saw that the liquid was indeed turning green, ie, solid
nickel oxide powder was becoming dissolved green nickel chloride.
Little or no heat, but lots
of visible fumes. After a while there was still black grit (which now
had to be broken up to stir). pH was still 1. Perhaps the solution was
saturated? I added some water to dilute it. A while later much of the
'black crud' was gone; pH was still 1. But I was probably just too
impatient, and now I had more water to evaporate off. Whyever, the
black layer on the bottom gradually thinned.
That was the simple part. But the liquid showed little
sign of evaporation in almost two weeks. I didn't want to move the
acidic trays with my nickel stuff down by the wood stove or anywhere
else where there might be extra heat - they might get dumped. Finally
it occurred to me that I might simply add the KMnO4 to the liquid, as
long as the acid was pretty much used up, which was accomplished by
adding some nickel hydroxide. The nickel permanganate - if that's what
it was - accumulated on the bottom, but it could hardly be collected. I
spooned some out, then had to wait for a lot of evaporation, then I had
a small tub of it, just 3 grams.
Much later in the month...
Resuming the great positrode chemistry idea after
interruption for developments to make cells that actually work in the
first place... The ratio
of manganese to nickel elements is two atoms to one. The atomic weights
of the initial ingredients are:
MnO2 = 54.9 + (16*2) = 86.9
Ni(OH)2 = 58.7 + ((16+1)*2) = 92.7
So the molecular ratio is: 86.9/92.7 * 2 = 1.87 (Mn) to 1 (Ni)
or 1.87 / 2.87 = 65 wt% MnO2, 35 wt% Ni(OH)2.
Since cycling in the battery would add and remove oxygen
substance, I wasn't very concerned about the amount of "O" in the
product, except for the fact that it could be an unknown in subsequent
calculations such as amp-hours per kilogram. Other than that, it just
needed to have two Mn's attached to each Ni.
PROCEDURE: The first mix was 1/4 that many grams of each, total
25 grams. I used pottery supply manganese since the graphite in
salvaged dry cell manganese would burn, (Hmm... is that bad, or just
free fuel?) I placed the mixed powder in a small stainless steel
pot, and heated the powder to glowing red with a swirljet propane
torch, going around
the pot several times. The powder
blew around in the pot when the strongest flame hit it.
RESULTS: I didn't think much of it blew out, but the
final product was about 15 grams. Some was black, and could possibly
have been unreacted MnO2 or NiO. But over 1/2 of it looked more
I think it was brownish right after the flame hit it, and it was
changing color repeatedly in the pot. Adding the initial weights: 92.7
+ 2*86.9 = 266.5
For NiMn2O4: 58.7 + 2*54.9 + 4*16 = 232.5 ; 232.5/266.5*25g = 21.8g
For NiMn2: 58.7 + 2*54.9 = 168.5 ; 168.5/266.5*25 = 15.8g
The product should have weighed more than 15g. Either most
of the oxygen
was driven off in the reducing propane flame or more powder blew
out during the torching than I suspected.
I tested the resistance by
pressing together on the meter leeds in the powder. Resistance was far
lower than Ni(OH)2 (in which I can't get any reading at all) but seemed
substantially higher than MnO2, and much higher than graphite.
I was hoping the conductivity would be such that graphite might be
dropped, making even smaller, lighter electrodes, but it doesn't look
Placed in water, the water
was clear. There was no sign of the purple permanganate
color, nor soluble green manganate or any dissolved substance. This
there's no permanganate, unless nickel permanganate is insoluble. It's
quite possible it's only slightly soluble, but purple should still have
been evident. The lack of green doesn't necessarily mean it's not
nickel manganate may be insoluble.
Despite the weight of the
product, the resistance readings are too high to suggest a metallic
(33%:67%) with no oxide was formed, so the substance must surely be
nickel manganate oxide of some sort, or a mix of two or more at varying
Still, the conductivity looks much better than nickel
hydroxide. (It's also much better than the stuff made by the liquid
process.) If it has the manganate-permanganate reactions, the amp-hours
and voltage should be
higher too. If so, the two common alkaline positrode substances
combined are considerably superior to either alone. But the nickel
reactions probably apply, being the lower voltage.
The next thing to do was to make a nickel-manganate
electrode from it and see what happened. It might be as fantastic as
envisioned or close via some reaction along the same lines, or it might
work about the same as a regular nickel electrode, or it might not even
Commercial interruption: since it did work, I made
more later. The second time, I tried 100 grams, 35 & 65 of Ni(OH)2
& MnO2. It was too much. I torched it all carefully, and when I
brought it in, the top was the blackish powder, but under that was the
original light grayish powder. I had to stir it and re-torch it several
times before I was sure it was pretty much all 'cooked'. Some powder
was in the outer catch tray, and it looked about the same - blackish,
'cooked' - so I dumped it back in. When I brought it in and weighed it,
there was 73 grams of product.
I'll happily make and sell it for other
experimenters/battery makers, seeing how it seems no one else does, but
given the cost of the ingredients (mainly the nickel), the yield of
under 75% so far, and the work of doing it, I think I'll want about
20¢ a gram. That can be reviewed later as I see how it goes. I
make no warranty of the composition of the product, much less the
purity, but it seems to work in my batteries. Gee, I can sell the whole
mix, ready mixed, for positrodes... Okay, same price. Now back to
For the first three electrodes:
* 11g nickel manganate (the torched stuff)
* 6g graphite
* .5g Ne2O3 for a bit
of rare earth [hydr]oxide to raise the oxygen overvoltage - better high
temperature performance, and if the
is the higher permanganate reactions,
it really may need it. (Oops, forgot to put it in.)
* ~.3g of some sort of binder 'glue' (Sunlight dishsoap)
That made 17 grams, but I had a gram or two left over, so about
5 grams went into each cylinder. It might have averaged 3.3 grams of
NiMn2O4 (if that's truly what it is) per electrode, 10 total. If it's
nickel valence 2 to 3 reaction it might total 1-2 amp-hours; if it
charges to permanganate, maybe 3-6.
After the substance was rammed into the cylinders, a 1/8"
drill bit was used to ream out a hole through the center. #14
grafpoxied wires were twisted and pushed into the holes and ABS caps
glued on. The PVC seams didn't glue with the methylene chloride solvent
- PVC needs MEK solvent, I think. But the ABS caps glued on fairly well.
I could try to melt the seam shut, perhaps with an iron.
But melted PVC vapour is notoriously carcinogenic, so it would be
outdoors with a respirator.
A Working battery! - just in time for my Ideawave talk
Two of these electrodes were tried with three
* 17g MnO2 with graphite (from dry cells)
* about 1.7% stibnite powder
I didn't add anything more to see if using nothing stopped
"all" self discharge. About 4 grams went into each electrode cylinder -
probably about 2-1/2 amp hours each - and I filled four of them, total
10 theoretical amp-hours. I then twisted in zinc coated (galvanized)
2-1/4" box nails for current collectors, and soldered zinc coated wire
to the nail heads with tin-silver solder.
Two positrodes and three negatrodes went into the same
upright battery case I made for two 1/2" electrodes. Four of each
didn't quite fit.
But first I had the three negatrodes in with the 1/2"
positrode. Cell resistance with this electrode had been unusably high,
and that didn't change with the new negatives.
So I was pleasantly surprised when I connected the first
of the new positrodes to find it had vastly better conductivity. Adding
the second one made further improvement.
The nickel manganate works great, at least as a new form
of nickel electrode with greatly improved conductivity. A
considerable amount of manganese has been used in most recent nickel
electrode formulations, eg, 25-40%. The additional amount of it in the
nickel manganate will probably be made up for in compactness and
reduced amount of graphite.
DIY battery makers are far more likely to be
successful at achieving cells that work than with poorly conducting
The cell was still a few ohms, but once a fair number of
electrode cylinders are put into one cell, low values should be
obtained. Or the flat plate with grill form can be adopted to get lower
values with smaller cells.
I let the cell sit overnight before trying to put a real
charge into it. It lost considerable conductivity overnight with the
electrodes just sitting immersed, but it still worked. I attribute this
probably to swelling of the electrodes - my usual problem - since the
seams of the cylinders didn't glue shut with the methylene chloride. I
methyl-ethyl keytone (MEK). It occurred to me belatedly that I could
have at least have zipped 2 or 3 cable ties around each electrode to
help hold them shut.
I charged up the cell starting on the 24th. It seemed to
be much the same as previous cells: when taken off charge, it began a
slow self discharge as usual, tho slower with the zinc plated
bringing the voltage down. Then I moved the battery, checked the pH -
neutral! - and added some electrolyte. When I glanced
at the meter, the voltage had gone from about 1.67 and slowly dropping,
to 1.933 and just sitting there... just like a real battery. I checked
the connections. No, no wires had moved over and started it charging
I put a load on it, and the voltage went down, and began a slow drop.
It recovered to over 1.9 volts... just like a real battery. After that
it continued to behave like a real battery, and continued charging
up to about 2 volts. (The voltage of nickel is nearly
+1 at neutral pH.) Whatever was dragging it down had suddenly ceased,
finally showing that whatever the problem was, it wasn't some intrinsic
flaw in the design or formulations. I soon found out what had happened:
two of the wires had corroded off the three manganese
negatrodes, leaving only one connected. Evidently, one of them (or the
was causing the self-discharge. At first I figured it was the solder,
even with the
silver in it, but then I realized that the bent end of the wires was
missing. The wire had corroded off the join at the bend, and the
soldered end was still there. Perhaps bending the wire to a right angle
had made a gap in the zinc plating. Anyway, when they fell off, they
dragging the cell down. Gaps in the plating on the bolts also doubtless
explained the slow negatrode self discharges of the earlier manganese
and zinc electrodes, too. (I'll replace those bolts and try those
electrodes again to verify that.) Luckily, in this last cell, one
electrode was a little longer and the solder join was above the
liquid, and at least that one nail was fully plated, or I might still
be in the
dark about the cause of the problem.
Okay, technique: I'll try silver-bearing solder even over
the zinc plated components prior
to use - don't trust the factory plating job! I have a feeling that
being able to melt zinc on the stove is going to prove valuable.
Perhaps the zinc:aluminum alloy [3:1] mentioned in the stovetop
metalcasting article may prove good.
But all the details weren't important for that moment.
after 4 years, the very afternoon before my
battery making talk at Ideawave, I had a real, working battery, with
the sort of optimum chemistries, voltage and energy density I'd been
When I returned home from the talk
the next day, it had charged up to almost 2.2 volts. That was in accord
with the reaction voltages given in the figures for salt electrolyte,
assuming the NiMn2O4 nickel reactions were similar to Ni(OH)2: +1V -
-1.18V = 2.18V. The next day (26th) it hit 2.3 volts. left overnight,
it discharged to 1.7 (rather than the usual .8 to 1.4 or whatever, so
it was an improvement).
The electrolyte was full of guck with a scum on top,
probably accounting for the remaining self discharge. I changed it,
which is evidently a normal part of making pocket electrodes. The pH
was a bit of a surprise: the negative side of the separator sheet was
mildly alkaline, and the positive slightly acidic. Other cells I've
made have turned quite alkaline all by themselves during charging. A
hydroxide charging to metal puts out lots of alkaline OH- ions. These
might be quickly absorbed into the nickel manganate, making it nickel
hydroxide manganate. Since neutral to acidic pH might mean that there
were soluble reactions occurring, I added calcium hydroxide to raise
the pH to 12.3 or so. But it didn't seem to raise it very much. On the
other hand, there were solids on the bottom of the old electrolyte, but
no dissolved color such as green that might indicate dissolved mangante
or nickel chloride. Perhaps nickel mangante, even if charged to (eg)
NiClMn2O4 or NiCl2Mn2O4 isn't soluble. But the amount of "Cl-" is
limited anyway (especially if it's done as a dry cell). Since it works,
it probably charges to an insoluble ternary oxide/hydroxide. Solidity
at neutral pH is a distinct chemical advantage. I have a lot of
question marks about pH and its causes and effects. If the worst comes
to the worst, that nasty KOH stuff works. Others have simply avoided
the whole issue by using that. But so far, the neutral KCl seems to
work fine too.
It was really a treat being able to open a battery, remove
the electrodes, rinse everything, repair a negatrode and put it all
back together again without any issues - try to do that with any other
battery construction! With the near neutral pH I didn't even need
gloves or eye protection.
Cell resistance and current drive obviously needed
improvement next. The reconstituted cell had two of each electrode.
With only a 66 ohm load (only about 25mA at 1.7V), the voltage
immediately dropped around 400mV. With one of the positrodes
disconnected, that became 600mV. With a negatrode missing, it was
around 450mV. This indicates that both types have low conductivity, but
that the plus is the side most needing improvement. The .4v drop / .025
A = 15 ohms is about the figure it has had since the electrodes first
swelled - it's not changing much.
At risk of repetition (of which I'm sure there's none
anywhere else) I'll remark that I expect conductivity wouldn't have
been high enough to make it work at all without the nickel manganate
replacing nickel hydroxide.
construction and compaction, a reasonable DIY target might be 2 or 3
ohms per electrode pair,
obtaining good current drive simply by having lots of the small
a cell. The first
thing for raising conductivity was to get the PVC electrodes to glue
shut properly so
the electrodes couldn't expand them and swell up. Then to
compact them really carefully and see if they fared better. Then to add
graphite, but there seems to be a limit to how much of it helps. After
I had one of each type electrode left. I heated the
plastic with a soldering iron and melted the seams shut on both
(wearing a respirator). I coated the lower end of the zinced wire with
tin-silver solder. Then I replaced two of the electrodes with these two
and left the cell to sit a few hours.
It occurred to me
that altho I had no 'standard
hydrogen electrode' with which to determine individual electrode
voltages, I could stick a copper wire into the liquid. With the pH and
a copper Pourbaix diagram, I could find the electrode voltage of copper
metal, and subtract that from a measured voltage to get the voltage of
individual electrodes. It appeared that in chloride solution (there
were four separate Pourbaix diagrams for copper in different solutions)
it should be -.13 volts from acidic pH up to about 10, but the readings
didn't jibe with approximately known figures. Maybe I should try zinc.
I checked out the perforations with a magnifying glass. In
any one view there were about 4 or 5 holes scattered around, which
looked like ugly gashes at 10x. In a metal pocket electrode from a
commercial nickel-iron battery, there were about two dozen neat, even,
rectangular slit holes in the same space. This could be a good part of
the cause of the low conductivity.
When I started charging it, the new negatrode was dragging
the cell down. I replaced it with the old one, so there were was only
one new positrode with the seam sealed shut and the other three were
the old ones. Still, one of the negatrodes had ten times the self
discharge of the other, impressing the need for (I assume) relative
perfection of higher overvoltage current collector coatings.
In spite of the sealed seam, performance seemed worse.
This can perhaps be attributed to the new electrode having a bit less
graphite powder than the others, perhaps 25% instead of 33%. Or perhaps
the sealed seam further reduced the electrolyte flow. Seemingly the
seam sealing made little improvement internally, which means that with
the stiff plastic and the small diameter of tube, the electrode doesn't
swell enough to make much difference.
So I'm going to go with the paucity of holes as being
likely to be a major problem, along with need for more graphite. I'll
make another one and try to do make more holes and use about 40%
graphite. I may be after that laser cutter soon.
If I have working
batteries holding lots of energy but still with insufficient current
drive to run the Electric Hubcap motor system well, I have the idea to
connect the new cells to sufficient NiMH
cells (or perhaps lead-acid cells) to run the motor, so that when the
system is on, they'll
continually charge the NiMH cells whenever they're below 1.38
volts/cell, ie, when the motor is drawing current or their charge is
down at all. This probably wouldn't work very well for continuous
highway travel, but it should for stop and go city driving. The minimal
NiMH (or PbPb) cells to get sufficient current - still five or more
banks of 30 NiMH D's,
which might provide up to 10 kilometers - would thus act as a buffer,
while the bigger (and cheaper... except for my construction time) NiMn
battery would provide the main energy for extended driving
But it should be possible to get at least as much current
from NiMn as from other types - and probably more with NiMn2O4
On the 28th I soldered my #8 nickel brass wire with silver
bearing solder (4.7% or 10% silver) to see if the original 1/2" square
size Mn electrode would hold charge instead of bubbling it off, using
the case and a couple of the Ni positrodes of the NiFe cell, in KOH.
The voltage in KOH electrolyte is lower than in KCl, charging to about
1.8 volts, since Ni is only +.49 instead of +.95 and Mn (for whatever
reason) is little or no higher than the neutral pH value of -1.18. I
found the total cell resistance was about 2 ohms. Doubtless resistance
mostly from my Mn 'trode, but if I was getting that from the large size
electrode, why was I making smaller ones that seemed worse rather than
So I may go back to the 1/2" size! If the holes are the
problem, it may just be that the 1/2" size has twice as many, since it
has twice the plastic surface area. Laser cut perforations should help
(either size) with denser hole spacing.