I'm curious as to how much of your description of ni-cads appplies to AAA, AA, C, D size batteries?
Hm. Well, these SAFT NiCDs I am using are flooded batteries. Small size NiCDs are sintered plate batteries, and are significantly different from the flooded ones.
Probably the biggest problem is that my batteries can have the electrolyte/water replaced, small cells cannot. The Safts also have a large amount of water in them, which can act as a "buffer" while charging. I can do relatively un-intelligent charging because if some cells go over they just vent a bit of gas. Every once in awhile I check the water level after a full charge and if they are low you add water.
This does not work with sintered plate. If they vent, that electrolyte is lost.
Another issue is that despite what I say you really can't parallel NiCDs too well. I get away with it because I am using two strings, and they gass to equalize. Not much honestly, but it happens. With three strings the discharge rates get a bit more wonky. But two strings is 80ah of battery. You would need eight 10ah strings of D cells to match that. And since the strings charge/discharge at different rates you raise the possibility of venting again.
I've built some pretty smart chargers to try and use Prismatic NiMH batteries from Prius packs. As in watch 10 cells at a time, temp monitor, delta T, as well as monitoring the change in voltage over time to pick up peak charge. And a timer. And a pulse "start charger" and pulse finish charger. They are *still* tough to charge properly. Stay away from small NiMH batteries, they are the devil.
I would recommend 40ah flooded NiCDs for elec-traks, but that's the smallest size. One pack is good for the lawn, two are good for tilling, and with three I can blow wet snow all morning long. I do not think I would recommend sintered plate NiCDs for anything other than experiments.
Chris tbamc wrote:
David, and Chris, etc.
Working temps, charging temps, leaving partially charged, etc. ? Thanks. Thon _______________________________________________ Elec-trak mailing list Elec-trak cosmos phy tufts edu https://cosmos.phy.tufts.edu/mailman/listinfo/elec-trak