The design for the Electric Hubcap motor and the (updated) design for the Turquoise Motor Controller are on the web. They are "finished" as far as the original intent to make a motor and controller that work for the drive system. I updated the motor controller manual again this month with a clearer schematic of the power MOSFET transistors and supporting components of the heatsink area.
A system to propel a car now only needs a working Carmichael Magnetic Torque Converter, the subject of the next section. The motor and torque converter unit now weighs 56 pounds.
I hope to improve the motor in the future with custom flat rotors having built-in hubs, to replace the car disk brake rotors and re-machined trailer axle hubs, and with microcrystalline coil cores.
The set-up for doing the rotors with abrasive waterjet cutting will cost money, but it will allow for thinner profile motors that are easier to make and somewhat lighter and simpler.
Microcrystalline cores would make the motor coils easier to produce, improve efficiency, and make the motors a little lighter. Of course, they depend on the success of the microcrystalline cores project.
The motor controllers provide great basic operation, but they can be improved by options for regenerative braking. This seemed impossible using the present MC33033 motor controller chip, so I wrote to ON Semiconductor, who make the chip, to ask if there's any variant of the chip made for electric cars that I'm unaware of, i.e. with regenerative braking, and if not, to suggest detailed ideas for such a new variant. There has been no reply.
But in the last days of the month, it dawned on me that there is probably a way to "trick" the motor controller into doing regenerative braking, by reversing the drive outputs or inverting the position sensor inputs, so the motor is being pushed backwards when the controller thinks it's pushing forward. It's likely to take an extra logic chip or two and some devious connections.
Of course, these improvements are minor details: these are working products and the instructions for making them are on the web. Presently, I'm putting my time into the magnetic torque converter, and (currently more so) into battery ideas and development.
Magnetic Torque
Converter Project:
Torque Leverage Without Gears
September Details
Torque Leverage Without Gears
September Details
In October 2008 I got a prototype Electric Hubcap motor to move my car across level pavement. It didn't seem like enough torque, so I made another one with bigger coils, and made some motor controller improvements, by early summer (2009). I realized then that the Electric Hubcap motor system just wasn't going to propel cars on the streets by direct motor connection to the wheel: there just isn't enough torque with this size motor even with the high torque design and supermagnets, to accelerate quickly and to go up hills - perhaps not even with a motor on each wheel. Now what?
Then I had the idea it should be possible to make a torque converter using supermagnets. I made what turned out to be an "electromagnetic coupler", but it couldn't have any more torque at the output rotor than at the input rotor, a fine point which had at first escaped me. In July I came up with one possible design. (I'm suspicious the induction technique wouldn't have worked well.) Then in August I came up with a completely new design. It had the advantage of needing the components I'd already made, with some additions rather than changes. This one should give some "magnetic punch", but again the details of actual operation are a bit hazy. A couple of fine adjustments would be critical. In September, some feeble attempts were made to fabricate it.
Near the end of September, I got another new design idea, to make a mechanism like a clock escapement. Again I haven't figured out an exact layout yet. In essence, as a magnet goes by and pushes the pivoting magnet ("escapement cam") away, it pushes into a slot with 45 degree sides. The farther from the motor rotor magnets it pivots, the less the magnetic force. When the force is less than the torque needed, they will slip apart.
However, such a mechanism again appears like it can be arranged as an addition to the original and the August designs rather than "instead of", so I'm continuing that one, however gradually. If it works well, I'll use it as is. If not, there's the alternative "escapement" idea.
A final late-breaking idea (Sept. 30th) is to angle the magnets 45º. This would provide a short range, almost a point, of powerful thrust when magnets meet, while also reducing the powerful (and worthless) attraction between the input and output rotors.
But on October first, the original (August) idea was together to a basically testable state and I ran it. It's promising, though noisy. Even though only two pivoting magnets out of six are installed, and even then are incompletely done and with a wide air gap to the other magnets, it takes very considerable force to completely stop the output rotor while the motor is turning.
Are there alternatives to the torque converter that could put Electric Hubcap systems on the road? Of course! One is planetary gears so the motor can be geared down, eg 2 speeds 8:1 and 2:1. This gets complicated and is doubtless inefficient, so two motors and two sets of gears would probably be needed, adding expense and decreasing electric driving range.
A second alternative is a continuously variable transmission ("CVT"). Here is one someone pointed me to that uses balls that roll at different angles depending on the shifter position and an oil that solidifies momentarily to provide traction when there is sufficient pressure on it, when the rolling ball meets its contact point:
The NuVinci (made so far for bicycles), and other CVT mechanisms and other alternatives,
make putting together a magnetic torque converter look so much simpler than when considering the project by itself!
September Progress
For the construction, first I tried to find rectangular stainless steel tube 1/2" x 1" (inside dimensions) to put the magnets in. No one seemed to have any, but I had an inspiration and I bought a piece of 1-1/4" round tube. Then I got a 1/2" x 1" steel rod to slip inside. I hammered the tube to the right shape on my big garden rock "anvil", and it seems ideal.
I also picked up 1/4" stainless round rod for hinge pin axles, 1/2" square stainless bar as hinge mounting pieces, and a piece of sil-fos (silver-phosphorus) solder. I drilled the bar with 1/4" holes for the axles and made threaded 1/4" holes for mounting bolts. Easier shown, below, than described.
Everything seemed to be going smoothly... then I went to solder the hinge pins on. I heated the stainless to bright red hot (like the guy where I bought solder said to do) with the 'swirljet' propane torch, but nothing would stick to it. Silver solder, sil-fos and brazing rod all beaded up and fell off! No amount of flux helped, and hotter MPS gas made no difference. I knew stainless couldn't be soft soldered (low temperature tin-whatever solder), but I hadn't realized that might also apply to silver solders and even brass brazing!
Reluctantly, I concluded there was nothing for it but to weld it. Not my favourite sport! I dug out the arc welder and all the paraphernalia and protective gear - I don't think I'd used it in a year or more. Then I proceeded to burn holes in and warp my nicely made parts! The pieces were smaller and the metal thinner than anything I'd welded before. By the third one of the three I'd made, I had the technique down: get the weld started and almost immediately quit!
Stainless steel magnet pivot cases:
first overheated by torch, then mutilated by arc welder.
The best pivot magnet assembly (never torched) mounted on "the ring" of the output rotor. Nothing sticks out past the outer edge. (or I'll grind it off.) Shown in "retracted" position. The magnet is inside. I haven't decided whether to put a bolt across the open end or just hammer it closed to retain the supermagnets.
The ring with pivot magnet in the output rotor, which gets attached to the car's wheel. The ring will be raised to about the top of the rim of the pan to leave more depth for the magnets to retract into. The input rotor magnets (rear face of the motor rotor) will spin by 'the ring' with a small air gap.
One detail that may become an issue is magnet gap: if it's too small, the motor won't start spinning. If it's too large, the torque won't be enough to move the car. Hopefully these ranges will not prove mutually exclusive!
The ring, sitting on the motor rotor, with two magnet assemblies mounted, Sept. 30th.
On the evening of Sept. 29th, someone pointed out to me that magnets slide past each other on the flat with relative ease compared to trying to pull them apart. He had a good point. Interactions between magnets are weird. If the coupling proves insufficient, twisting the output magnets by some angle such as 45º would give the whole system more punch in the radial direction, while also reducing the more powerful (and useless) attraction between the rotors as magnets pass by each other. (In fact, this is probably a good idea regardless - sigh, back to the drawing board!)
On October first, I finally put everything together (as it was by then already made). First I had no magnets in the holders, but the bolts were magnetic steel. I put it on the axle with the motor rotor and turned the motor rotor by hand. Somewhat surprisingly, the output rotor, though resting on its four bolts on the bench, bumped along, turning a bit at a time as each magnet went by a bolt. A steady turning pressure of the force applied would have been insufficient to move it, but the same average force, split into the periodic strong magnetic "bumps" with the longer times with no force in between, did it. And there was certainly not enough time between bumps for a car to roll back again if it had been moved. This seemed like a good sign!
In fact, it gives rise to the idea that simple pivoting blocks of steel retracted by springs, instead of supermagnets, could be used in the output rotor. Of course, supermagnet against steel would have much less punch than supermagnet against supermagnet.
I put the magnets in and they clacked up and down as the rotor turned by them. Then I put the motor together and ran it. With the motor turning at a fair power, I put my hands (leather gloves) on the output rotor and held it back. It was very noisy with the magnets clacking up and down fast!
It had quite a bit of torque, but I could stop it by hand. It probably wasn't enough to move a car (though I wouldn't swear it wouldn't have on level pavement either), and I can't say for sure that it had more torque than the motor by itself. On the other hand, there were only two magnets installed, the air gap was 3/4", and I hadn't installed the magnetic catches. Six magnets with 1/4" gap and pivoting at the optimum times ought to be another story.
Running the motor at a lower power level, it would stall when I stopped the output rotor. This is probably largely a result of my skewed motor magnet arrangement. I'd redo that if epoxy glue wasn't so hard to get off, or if I felt I could afford another batch of magnets.
I want to devise a mounting system and try pivoting the magnets the other direction, at a 45º angle, before making more magnet holders of this type. Checking magnet interactions by hand, I can tell there'd be much more "punch" at that angle instead of flat, so it should work better - and more quietly! It has yet to be proven, but I expect it should shove a car even up a good hill.
Microcrystalline Electromagnet Coil Cores
September Details
I decided I shouldn't let a month slip by without at least attempting one core -- lest I forget what mineral is what and what they're for! And I had obtained one additional material I wanted to try after a bit of reading: barium carbonate. Barium titanate is a compound often mentioned as a ferrite core, although more as a 'hard ferrite' that retains magnetism than as a soft one for electromagnets.
There's titanium in the ilmenite, but no source of barium in what I'd been using thus far, so cores #20 and #21 had as "active ingredients" laguna borate, magnetite, ilmenite and barium carbonate. The carbonate "calcines", sheds its carbon to the air above - um - some temperature:
BaCO3(s) => BaO(s) + CO2(g)
In with all in the clay, I expect some barium titanate will be formed in the firing because, um... Ah, here it is:
"Solid-state reaction between BaCO3 and TiO2 in an equimolar ratio at temperatures >1200°C has often been used to prepare BaTiO3 powders."
Of course, ilmenite isn't TiO2, it's FeO:TiO2. Oops... on writing the above, it seemed I'd already gotten too much out of touch with the project: RUTILE is TiO2! Ilmenite might work anyway as it contains titanium, but I went off and mixed core #22, with rutile instead of ilmenite!
Well, none of these cores worked. What am I missing? On the other hand, I didn't heat it to 1200ºC, either. I didn't want to heat the other ingredients so hot.
I suppose I could try mixing some BaCO3 and TiO2 powders and heating them separately to over 1200 C. But would I know if I'd succeeded, and would BaTiO3 make for a successful core when nothing else has?
What am I looking at?...
TiO2: white powder
BaCO3: white powder
BaTiO3: "white crystals" (Wikipedia)
Here's something interesting about manganese and magnetism, which element I was looking up for battery info:
"With aluminum and antimony, and especially with small amounts of copper, it [manganese] forms highly ferromagnetic alloys. [And presumably could make "superparamagnetism"? The authors speak of metallic alloys, not oxides. I now have 5 pounds of manganese powder on order for batteries.]
But perhaps I'll refrain from making any more cores pending some additional understanding or an idea for a fresh approach to try out.
(To the point for batteries, with respect to self discharge: "The metal is reactive chemically, and decomposes [in] cold water slowly." ...But does "slowly" mean hours, or years?)
September Details
Good Cellophane!
Though having got no answers from the company about the product by e-mail, I bought some "Pacon" brand "clear" cellophane from amongst several "coloured" types at Island Blueprint, and to my surprise it appears to be the real thing: uncoated microporous cellophane that breathes. When I suck on it, cool air very gradually comes through it. And it makes an ionic connection instead of a very high resistance inside a battery: it works!
Having found microporous cellophane at last, I see it probably isn't the whole answer, because my batteries still won't retain a charge.
Perhaps a potassium and chlorine ion permeable membrane - a "salt bridge" - that won't let too much else through may be key. That way, dissolved metal ions will stay on their own side and can be used, rather than all charge and discharge reaction products (other than the electrolyte) having to be insoluble solids.
The battery book has a few notes on semipermeable membranes. They're okay starting points, but vague on exactly what and how in a mostly quite explicit book. This probably represents the unsure, groping exploration that had been ongoing and probably continued until the lithium juggernaut evidently pre-empted all other battery research.
I decided to try out my acetaldehyde and acetal ester tricks for preparing the surface. I used an artist's brush to brush acetaldehyde (fresh batch) onto a piece of cellophane. Then I brushed in some ferric oxide, then I brushed in some 20% hydrochloric acid to turn the acetaldehyde into an acetal ester. Notwithstanding that this cellophane is permeable, I turned it over, did the other side the same, then sprayed some seal oil on that side.
It didn't seem to work any better than a regular untreated sheet.
In order to have cases with a minimum of seams and a maximum of strength for battereis that will hold a certain amount of pressure, I started making and trying out improved jigs for turning round pipe into square in the oven. The maximum temperature to heat the oven to is around 150 C / 300 F. That, of course, is according to my oven's dial. Somewhere not much higher the ABS started sticking to the base it's on, and probably soon to the other jig pieces as well.
Two inch I.D. ABS drain pipe can just be coaxed into making a 3.2" x 15mm (5/8") rectangular case (inside dimensions) for a single 3" wide cell, though considerable stretching of the plastic is needed to accomplish this since the original circumference is 2 pi (6.28) inches and the final lengths add up to 7.25".
I found a pressure meter and an adjustable pressure relief valve at Coast Industrial Supplies. The meter is finally starting to tell me just what pressures are in fact building up inside my batteries.
Two inch pipe made into a 3" wide battery case. The skew was an unexpected feature of the stretching/squaring technique.
This finally made a well sealed battery, one that can be opened by removing the clamping bolts. It held 34 PSI!, but not without a rubber gasket and some wooden pieces under the metal lid to spread the force of the bolts.
Two short 1/4" stainless steel bolts, their heads screwed up tight against the lid on the inside, worked for sealed terminals. I had to drill small holes into the heads and thread them for #6 screws to allow a connection to be bolted to them on the inside.
The most extreme internal pressure measured - after charging at a high rate - was 34 PSI. At that pressure the sides of the case were bulging and bending the side bolts out, but it held!
I must mount the pressure relief valve next time! I'll probably set it at about 15 PSI.
I thought a three inch I.D. pipe should work out quite well for three inch wide plates batteries without such exertions to stretch the plastic as well as square it. However, it seems a four cell enclosure would again require some stretching while the plastic is hot. Perhaps I should just settle for three cells per battery. or thinner electrodes, which would also be higher current capacity.
Here is an attempt to make a squaring jig for 3" tubing. It needs 8 bolts:
A jig to make round 3" ABS pipe rectangular. Using the two types of former pieces, square bar and angle iron, resulted in a somewhat skewed diamond shape, not quite a rectangle. It is also a bit under 3" across the long side instead of a bit over. The next one will be wider but thinner.
The tube, with rough ends and then with the ends sanded. Even with slightly rounded corners and skew, this is a much better shape for flat battery plates than a round pipe!
The next version will have four identical corner formers and a better system of pushing them apart. Four of the eight wing nuts can be on the outsides as long as they aren't over 3" long, but one end has to fit through the 3" tube before forming. At least a couple will have to be removable so the jig can pass through the unformed pipe.
With the formed case sides rectangle, the only seams are at the top and bottom joins, much improving the chances of getting a sealed battery.
After forming, the cases are sawed flat top and bottom (if necessary), and then sanded very flat and smooth. Inspect for complete flatness with no unsanded areas. Set the flat top or bottom piece onto the case. Hold it up to the light, and if you can see any cracks of light between the pieces, re-sand.
Once satisfied, dip a "q-tip" in the "aerogloss clear gloss" model airplane dope glue (or other ABS solvent glue) and carefully coat the entire rim of the case with no gaps. Put on the bottom cover piece. Carefully weigh the assembly down or clamp it, to press the two pieces together firmly at all points until the cement sets.
Of course, if I could simply find injection molded cases - or rectangular plastic pipes - of suitable material, size, shape and wall thickness, it would make forming them in the oven superfluous. So far, I've had no luck.
Another idea that occurs to me to try out in October, now that I've thought of heating the plastic, is to make cases from flat pieces and then heat them in the oven until soft, perhaps arranged with weights pressing the seams together. A bit of "melting together" might just impart the needed strength to the joins, including the top or bottom cover. This might - possibly - be easier, and would provide complete control over the dimensions. (On the other hand, I find making every edge of every piece perfectly straight and smooth so the seams are "seamless" isn't trivial even if they can then be made strong enough. Somehow, Plexiclass does much better cuts than I do - it might work out well if I have the pieces cut there.)
Until now I've been putting "uncharged" chemicals in my batteries. In reading I've seen people putting chemicals in in charged condition. Nickel hydroxide is bleached with 10% NaClO to oxidize it to nickel oxy-hydroxide, and metallic zinc powder is used along with some zinc oxide. Since the battery is supposed to be positive limited to prevent hydrogen gas production (ie, the nickel's charge runs out before the zinc's does), it makes sense that perhaps some of the negative electrode should be installed as the metal, the "charged" condition, even if the positive is uncharged.
Plus, the only battery I've made that's really worked so far is the nickel-iron one, in which the iron electrode had some steel (impure iron) filings in it as well as iron oxide. (And it turns out Fe2O3 was the wrong oxide: purified Fe3O4 powder is the right one.) Perhaps using some "charged" negative material is a key to success?
I bought a chunk of zinc and sanded some zinc powder off it, but I think manganese could make a better negative electrode and couldn't find anywhere in town to get manganese powder (or metal), so it's turned from a simple $30 sample purchase into a $350 US import, counting getting some more monel powder as it's the same company (micron metals) and I'm almost out anyway. Manganese dioxide is available at pottery supplies and I have some, but this is an (overly) UNcharged state for a negative electrode.
For a negative electrode, manganese seems to have great potential energy in alkaline solution: about 1.5 KWH/Kg. That compares favourably with zinc at about 1.0, the best metal hydrides at about 0.8 or cadmium at 0.4.
That's without counting the OH's in the compounds and in practice none of these theoretical figures will be achieved, but the manganese looks like a very good bet! I think the reaction voltage of -1.56 volts should be okay -- after all, the lead oxide <=> lead sulfate reaction in lead acid batteries is +1.68 volts and that works. But if it proves a bit too high in alkaline solution, it could work in a salt electrolyte (probably around -1.3v), still a higher voltage than zinc (~ -1v).
139/58.7
Mn + 2OH- <==> Mn(OH)2 + 2e- [-1.56v]
The discharge reaction may carry on to Mn valence III in alkaline solution:
Mn(OH)2 ==> Mn2O3 [-0.25v]
or just possibly:
Mn(OH)2 ==> MnO2 [-0.05v]
It is also possible the reaction, in alkali electrolyte, may proceed straight from Mn to Mn2O3, and the voltage is likely to be lower rather than the sum of the two valence changes, perhaps -1.4 volts instead of -1.56. But then it should move 3 electrons per Mn atom instead of 2, multiplying the amp-hours by 1.5 and reducing self-discharge, so that could actually be an advantage.
Manganese has a confusing array of reaction possibilities, but the reaction products mentioned for a negative electrode are all solid and likely to be trouble free. In salt solution, reaction is likely to end at valence II as going to III will no doubt become a positive voltage reaction instead of weakly negative.
Edison used lithium hydroxide to improve the conductivity of his nickel hydroxide positive electrodes. How it works evidently isn't clear, but it does. I've decided to try it in both nickel and lanthanum electrodes, and also perhaps in the lead-acid batteries, where it might help desulfate the lead oxide plate.
I couldn't find lithium locally except as carbonate. (One store can sell this over the counter, at another you need a "prescription" to buy it - such is Canada's maze of arbitrary chemical restrictions.)
It turns out the hydroxide can be made from the carbonate by putting it in solution with calcium hydroxide in a swapping reaction. I weighed the ingredients carefully so as to have very little left-over unreacted stuff:
Li2CO3(aq) + Ca(OH)2(aq) ==> LiOH(aq) + CaCO3(s).
The calcium carbonate precipitate is filtered out, leaving the lithium hydroxide in solution in the water. I bought a coffee cone filter at Cairo Coffee to filter it with. (The merchant made the mistake of asking me how I planned to use the coffee filter - I doubt the answer was at all what he expected and he offered little advise!)
The only things that aren't clear are how much water to use and how long the reaction takes... seconds? minutes? weeks? Too much water and the LiOH will be dilute, too little and it will all be somewhere within the sediment, or even some will come out of solution.
I also had to buy calcium as carbonate rather than as hydroxide. The procedure for converting that is simply to put it in a pottery kiln and "calcine" it:
CaCO3 + ~900 degrees C ==> CaO + CO2
100 grams of CaCO3 shrinks into about 56 grams of CaO, giving off 44 grams of CO2 (that's ideally - I get about 57-58 grams). This calcium oxide ("lime") turns into hydroxide ("slaked lime") spontaneously in water. The temperature at which lithium carbonate calcines is too high for this direct method. (Calcium also has the interesting property of losing an electron, and, juggling the empty spot back and forth, can ride light beams and thus escape from the sun to wander through space.)
In theory, I can dry and re-convert the calcium carbonate to hydroxide again after making the lithium hydroxide, ready for the next batch.
New: The Lead Battery Project
September Details
Inspired at the end of August by stories of people reviving old lead-acid batteries with alum and epsom salt, I decided to look into the idea myself. The possibilities for improvement of the venerable lead battery seemed exciting:
1. If they had a higher current capacity, as some were saying they seemed to have, that would have some beneficial effects:
a. A smaller battery could start a car engine, potentially slightly reducing vehicle weight.
b. Fewer batteries in parallel would be needed to provide enough steady-state current for electric driving. This could reduce the weight of batteries needed simply to get the car to operate well.
c. At a given current, the amp-hours would be increased. Lead-acid battery capacity (amp-hours) is usually rated for gradual discharge over 20 hours. Used up in one hour of electric driving, the amp-hours actually available might be only perhaps 60% of the rating. With greater current capacity, the rate of discharge should be less limiting - maybe 65% to 80% might be usable.
2. There seemed to be promise of increased voltage as well. 15 volts instead of 12 would mean four batteries in series would replace 5 for 60 volts, for example, a 20% battery weight savings. Higher voltage would be set by adjusting the pH of the electrolyte.
3. Much of the ongoing cost of electric driving is for replacing batteries. Tripling the life span, as is apparently the least expected, would dramatically cut that cost.
4. If lead-acid batteries are discharged too far, they are soon ruined. It seemed likely that they could be made less "fragile", less prone to serious damage from overdischarge.
For a "best case" view, saving 20% of the battery weight by higher voltage and 20% of the remainder by higher current yielding higher amp hours is a total of 36% less weight or 36% fewer batteries, eg, 1000 pounds becomes 640, or twenty 50 pound batteries becomes 13. And a 400 pound vehicle weight reduction itself should save at least another battery, so make it 12 batteries, 600 pounds.
And if the fewer batteries should last four times as long, long-term battery replacement expenses would be just 15% of the previously expected amount!
What experiments over the month showed was that adding sodium sulfate (or sodium hydroxide) cleaned the battery, evidently removing corrosion and sulfation, but that the pH always went back to 1, so there was no way to up the voltage or to operate the battery at a less hazardous level of acidity.
Those who aren't interested may wish to skip "The Experiments" and go directly to the tentative directions for renewing batteries.
Initial results weren't quite what I expected, but I figured out much of what was happening, realized that most people wouldn't, and realized that sodium sulfate would work better than alum or epsom salt. Seems I've learned some chemistry from my other battery work. So I decided that it would be worth a diversion from other research to make a small project out of it, the Lead Battery project. I hope it'll be a short project.
Ah, here's the name... Feng Yuesheng would appear to be the person who discovered that using alum instead of sulfuric acid helps "restore" lead acid batteries.
One thinks, "Wow, salt instead of acid! Way safer!"
However, this is evidently not the case. After filling a battery with epsom salt (magnesium sulfate), which has a pH of around 5.5-6.5, and charging for perhaps 1/2 hour, I checked the pH and found it was 1 - strong acid! The magnesium was probably on the bottom as insoluble magnesium hydroxide.
Apparently the charging-discharging reactions still make sulfuric acid, using hydrogen from the water and sulfate from the salt. That means the cation(s) of the salt are "left over" in the reaction, and would make hydroxides. [Below, HOH = H2O. Water breaks down into "H+" and "OH-" ions, so I like to think of it conceptually as H-OH.]:
Alum: NaAl(SO4)2(aq) + 4HOH(l) => 2H2SO4(aq) + NaOH(aq) + Al(OH)3(s)
Epsom Salt: MgSO4(aq) + 2HOH(l) => H2SO4(aq) + MgOH2(s)
Aluminum and magnesium hydroxides are almost insoluble - they'll settle out on the bottom. The one sodium hydroxide of alum will remain in solution. It's alkaline and it's probably a reason for improved performance, but it doesn't balance out the two molecules of acid and the pH will remain near the bottom of the scale.
Somehow adding epsom salt to the acid evidently renews the battery, but the electrochemistry actually appears to be unchanged. Perhaps simply the increase of acid is what was needed. Or, it may - possibly - be that the magnesium hydroxide settles on the surface of the plates and improves the conductivity of lead sulfate so the battery gets "desulfated". This is more doubtful.
The sodium sulfate is a different story because sodium hydroxide is soluble:
Sodium Sulfate: Na2SO4(aq) + 2HOH(l) => H2SO4(aq) + 2NaOH(aq)
Theoretically, the acidity and the alkalinity cancel each other, leaving pH = 7, neutral.
In fact, the two products should recombine spontaneously to make salt solution and water again. Instead of replacing acid with sodium sulfate, which I'd ordered but it hadn't arrived yet, I tried adding sodium hydroxide solution to a battery that already had acid in it to derive the salt. ("Caustic soda" is dangerous - see instructions below) I used the hydrometer to siphon some acid (also dangerous) out of the battery, bringing the level down to the plates. Results, on a battery that wasn't working well anyway and turned out to have a leak, were inconclusive.
Finally the pre-made sodium sulfate salt arrived. I added it to warm water to s.g. 1.25. Not surprisingly, it took about 5 liters and over a Kg of the salt - about 30 $ worth - to fill one battery. The NaOH is much cheaper. But it turns out simply adding some to the battery rather than replacing the existing acid is best.
The solubility of sodium sulfate is of interest: according to Wikipedia it rises tenfold between 0 and 33 degrees C from 50 to almost 500 grams/liter, and then doesn't change much above that. The battery may have poor low temperature performance, and may be more subject to freezing in cold climes.
The "usual" lead-lead battery half reactions with "hydrogen sulfate" electrolyte are:
PbO2(s) + 4H+ + SO42- + 2e- <--> PbSO4(s) + 2H2O [+1.685 v]
PbSO4(s) + 2e- <--> Pb(s) + SO42- [- 0.350 v] (1.685 - -.350 = 2.035 v)
The voltages obtained with lead reactions tend to rise with pH, as seen on this chart from webelements.com:
Since voltages above 2.0 can't be used in aqueous batteries, it seems evident that the lead-lead battery can't be an alkaline battery. However, I suspected that by raising the pH somewhat with some acid and some sulfate salt, voltages above the pure acid ones could be obtained. Perhaps at pH between 3 and 6 we might see the positive voltage go up to, say, +1.8 from +1.65, and the negative from -.35 to -.5, yielding 2.3 volts per cell or 13.8 volts. Unfortunately, it probably isn't practical to go much higher with the positive electrode. +1.9 volts might be just workable if the charge is slow so that 2.0 volts isn't reached. The cells might then be 2.4 or 2.5 volts - 14 to 15 volts per battery.
At neutral pH (7.0), the battery bubbled strongly as it was being charged. Evidently, the voltage of the positive reaction is too high at neutral pH and the water was making gas instead of the positive electrode charging. This was not unexpected. [Later note: Actually, they bubble like coffee percolating coffee as soon as the NaOH or Na2SO4 is added even without charging, for quite a while, giving off SO2 gas. This is probably the desired cleaning action that renews the battery.]
I added a some concentrated sulfuric acid to each cell ("1/4 cup" according to the measure), but the battery still bubbled, and the experiment was halted for want of pH test paper. I had tried to buy some at "Science Works" a day or two previously, but they were out and I didn't know of any other supplier in town. I hadn't counted on that! I diced up my last two strips into "microchip" pieces, but they didn't go very far. The next day I found Van Isle Water Supplies had pH test paper (after being directed fruitlessly to garden stores, wine making places and aquarium stores). They looked very nice, but it was over $40 for a pack of 100 instead of $4! I decided I'd just have to wait for Science Works. Anyway, it would seem better to have something to discern between pH 0.0 to perhaps 5.5 in fine increments rather than these broad range papers, where it reads "somewhere between 1 and 3". When Science Works finally got some in a couple of weeks later, it was only a few jars and they'd only sell me two for now because others were also waiting for some. The pH test paper famine continues in Victoria, now with rationing!
Then, still without being able to check pH, I tried another "deep cycle" old "dead" battery, adding "some" sodium hydroxide to the acid. After a couple of charges and partial discharges, it seemed to be working quite well. The voltage seemed no higher though.
I tried adding a little lithium hydroxide (made per "Turquoise Battery Project" above) to this battery to to see if the current capacity might be increased - it worked for Edison, though in a very different kind of battery. I'll determine the current capacity just by seeing what the immediate voltage drop is when a heavy load (eg 25 amps) is turned on. Surely the less the drop, the better the current capacity. But I doubt it had much effect.
If the current capacity is increased, not only can a smaller battery start a car engine, but the effective amp-hours & watt-hours available at the continual higher loads of electric driving will be increased, giving greater driving range, or the same range with fewer or smaller batteries. Almost the same comments could be made about increased voltage.
The batteries I've tried so far have been "brought back from the dead" by the conversion. That's less of a feat than Jesus' raising of Lazarus of course, but still it's a surprise that it should be so simple given that everybody "has known" for over 100 years that they "can't" easily be restored. Knowledge is power!
The last battery done, on October first, had a bad internal connection. It sat at about 10.7 volts, and connected to four headlights, it instantly dropped to about 5 volts and made arcing sounds. After treatment, it would stay at 12.7 volts and it lit several lights fine. Though it still didn't hold much charge, the bit it had increased 60% between the first and fourth load tests, with some hours of trickle charging in between each test.
1. Get a battery hydrometer (auto supply, eg Canadian Tire), rubber gloves (Grocery) a face shield (Builders Supply) or at least eye protection goggles, and some sodium hydroxide (NaOH, caustic soda - Borden Mercantile gardening supply or a soap making supply). (I presume you have a lead-acid battery.)
2. There are two alternatives: use sodium sulfate salt directly (drug store or compounding pharmacy) or make it using sodium hydroxide. I'll describe using the hydroxide here for now because it's what I've mostly been doing. The salt is safer to handle -- it's been used as a laxative. But it will only go to around 1.125 density when dissolved unless it's heated up to about 35ºC, at which temperature it's much more soluble.
3. Put on the face shield (or at least eyewear) and rubber gloves. Fill a jar with pure water, not to the brim, and put it in a sink. With a small scoop, slowly add sodium hydroxide powder while stirring. It takes minutes not seconds to dissolve, and during that time it gives off heat. If you add too much too fast, a plastic jar may melt or a glass one shatter, or perhaps the water may boil. The powder and solution (it's also called "caustic soda") is corrosive to skin and will blind eyes. When the water clarifies and isn't too hot, you can add more powder. Check with the hydrometer and stop when the specific gravity is about 1.25 or so. I tend to add half, go have a coffee or something, then come back and add the other half.
3. Put the lid tightly on the jar and rinse everything: sink, jar, scoop, gloves, counter. Put away the caustic soda powder.
4. Now to the battery: In addition to face shield and gloves, shield bare skin. Old clothes or coveralls are an asset. Place the battery outdoors or in a sink (bathtub?) where a spill won't do much to anything. (Remember the acid will etch and eat stainless steel if it doesn't get rinsed off.)
5. Siphon acid out of the battery down to the plates with the hydrometer, into a jar. Put the lid on the jar. (What to do with the acid??)
6. Add some sodium hydroxide, an equal amount to each cell. I'm guessing 80cc per cell for a small car battery - maybe a couple of hydrometer fills worth. Keep the liquid level fairly low, not far above the tops of the plates. Leave the top covers off the cells!!! (Otherwise, it might explode, spewing acid!) There will be a strong bubbling, percolating action, bubbling off sulfur dioxide gas. This seems to be the cleansing and renewal of the battery.
7. Charge the the battery, preferably still outdoors. It may bubble furiously the first 2 or 3 charges and the covers may still 'explode' off if they're pushed on - that's dangerous.
8. Do some charges, and discharges down to about 11(?) volts to recondition it. I use a halogen car headlight or two or four for a load - they draw about 3 amps each... and if placed strategically the light will remind you not to accidentally leave the battery running until it's dead again.
At some point the bubbling will be reduced to the point where it is safe to replace the battery covers. It seems no matter how much salt or alkali is added, after the bubbling the battery pH is 1: strong acid. Thus, there's probably a limit to how much sodium sulfate is useful or desirable. Another question is: Does it just act once, or is there an ongoing anti-corrosion or other beneficial (or otherwise) effect?
BTW: If you notice a white powder around the battery holes: if it's long thin "needle" crystals, it's sodium sulfate salt (Na2SO4) formed by the acid (H2SO4) and the hydroxide (NaOH). (The other product of this reaction is H2O) If it's simply powdery it might be NaOH, nasty hydroxide, AKA "caustic soda". (If there's liquid it might be anything.) Whatever... put the covers on the holes after it stops bubbling and hose down the battery.
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Victoria BC