I've used a row of vertically mounted edgewise analog meters to monitor the modules in a battery. This was in my 1980 Comuta-Car. When, not if, the car's battery developed a stinker module, I could see it instantly, though not at night, since I never fitted illumination to the meter panel. Veteran EV list correspondent Lee Hart had a better idea that immediately solved the illumination problem: replace the meters with LEDs. Day or night, an extra-dim LED is even easier to spot than a low meter reading.
Yep, I think this design was a modification of the Lee Hart concept (guy loved zeners) with a "hey, LEDs can light in both directions now!". The only drawback was that it pulls about 10ma when idle all the time, which can of course kill a lead acid battery over say a winter. But NiCDs don't care about going to zero, in fact they love it. So I think I'll look around for some of the PCB boards and build another one or two.
Working today I found that after a full charge zone 2 was reading about .4 volts under the other two under load (idle gear, motor at max speed for a draw) which was odd. I checked the cells and sure enough one was at .9 volts when measured from the neighbors, but 1.3 volts when measured at its own posts. Yep, one of the interconects was dropping .4 volts. Pulled it and found the contacts needed cleaning. A quick cleanup and now all are good
Yeah, totally not good. I have the feeling this one was just providing power backwards, sub optimal to the extreme.Thoughts about your reversed cell: NiCd cells can handle reversal much much much better than lead cells, but it's sure not healthy for them!
It was at zero with the motor load when I pulled it, however it was not shorted and had resistance.If you want to try salvaging that cell, I'd suggest taking it to zero SOC with a suitable resistance and then a shorting bar. I might leave it at zero for a few days.
Apply a (forward!) constant current charge of around C/20 to C/10. That is, for a 34AH cell, 1.7 to 3.4 amps. Charge until the cell has consumed 150% of its rated amp-hour capacity, ie, 15h at C/10. You can let the voltage rise to about 1.8 volts.
*nod* after 10 hours it's at 1.5vpc and I have to stop as I am going out for the evening. I'll put the bench supply on the one replacement cell in the E15 this evening and let it go at 2a overnight as a finishing charge.
Thanks for the thoughts and the time taken to put them down David. Glad you're around; these Elec-Trak's plus BB600s will last forever. :-)