Turquoise Energy Newsletter #27

The Electric Hubcap^TM Vehicle Drive System
March Details
A New Drive Configuration and Back

As

Mechanical Torque Converter Project:
Torque Leverage Without Gears
March Details

A

Nanocrystalline Ceramic Motor Coil Cores Project

Thi

Ocean Wave Power Project
March Details

In

Turquoise Battery Project

The Ni-Mn Alkaline Cell: April Experiments

   I took apart an old 'dead' (shorted) Ni-Cd cell from a cordless drill battery pack, and unwrapped the spiral electrodes. Rough dimensions, flattened:

Ni(OH)2 electrode: 35mm x 19cm x .7mm
Cd(OH)2 electrode: 35mm x 21cm x .6mm

   The separator paper seemed to be just a few fibers left stuck to the electrodes. It seemed so thin and insubstantial I wonder how it could ever work in the first place. No wonder most Ni-Cd cells end up shorted out! But I guess the thinest separator allows the highest current per square cm. I get to try out things selecting from (a) cellophane (b) the 90 weight heavy watercolor paper (c) woven nylon cloth (d) woven polyester cloth (e) fibreglass mat (f) writing paper or other thin papers (g)rayon nonwoven.
   I put the electrodes in small bottles so the CO2 in the air wouldn't convert their KOH electrolyte into K2CO3. (I hope that's good enough - there is some air in the bottles!)
   The battery case was strongly crimped in to force it to seal against a nylon ring at the open "+" end. It seems one must actually go to extremes to achieve a good seal, and we know that even then some batteries leak, though none of these eight appear to have.
   I can use the one still working cell as a benchmark, to see how many amp-hours the batteries are supposed to have (I predict about one), and how much current they ought to deliver with how much voltage drop (I prophesy around 3.5 amps for 1.0 volts - 50mA/sq.cm). Those measurements will tell the current per sq.cm and the energy per cc. The nickel electrode volume is about 4.5cc. According to "typical", that should mean maybe 7 grams of Ni(OH)2. At 200mAH/g, 1.4 AH. That would mean a 10 hour discharge rate for testing would be 140mA, so the load resistor, for 1.2 volts, is 8.5 ohms. I'll use 10 ohms and see how long it lasts.
   I note that the electrodes of this "little" battery, 3.5 x 20 cm = 70 sq.cm, are over half the area of the ones I've been planning for my "big" EV batteries, 3" x 6" = 116 sq.cm. Maybe I should be re-thinking this whole thing! Perhaps I should be considering making single cells with rolled up electrodes to get the large surface areas. big cylinder batteries 6" long with 18" long spiral electrodes, in, eg, 1-1/2" round pipe. It would still take four cells in parallel! (and about 20 in series for 36 volts under load, 80 cells.)
   Here again, I expected much higher currents from the perchlorate chemistry and 3"x6" might well be enough (or 2 or 3 or 4 of them), making multi-cell batteries of, eg, 12 volts, whereas with alkaline cells, 125 amps at 50mA/sq.cm is going to take, um, 2-1/2 square meters per cell.
   For large surface area wound-up electrodes, the compactor seems inadequate - it would be very tedious. perhaps some sort of 6" long roller sliding on a track over a thick 18" slab of steel, to compact them by rolling over the materials, will be required.

Lead-Acid/Sodium Sulfate Battery Renewal Project
April Details