On Tue, 26 Apr 2005 22:55:44 -0400, Mark Cassino wrote: > Ah - so Amps are purely additive - so many amps per hour, there you go....
Weeeelllll, amp-hours (Ah) are additive. 5 amps for one hour is 5 Ah. 1 amp for five hours is still 5 Ah. Amps (current) can combine in several different ways depending on serial versus parallel circuits and that sort of stuff. > I pulled the battery off the charger and will see how it works tomorrow. You might need to cycle it a couple of times to "bring it back to life" depending on the battery technology. I don't know squat about lead acid, NiMH, or L-Ion batteries, because I haven't ever driven them to the brink of destruction and brought them back. But I have done that to NiCd batteries. I have found that on NiCd batteries, in some circumstances, excessive overcharging, like I think you might have done, can raise the "noise floor" to the point that the useful life of the batteries is severely degraded. Our application (R/C cars) was "special" in that we were more focused on getting the energy out of the battery quickly. We wanted to go from maxed-out capacity to stone dead in four minutes and two seconds (the heat races were four minutes long). When the "noise floor" rose in our NiCds, we'd dead short the leads across a small value (1-100 Ohms) resistor of several watts capacity for a while (usually a day or two) to gradually bring them down to the vicinity of 1.0V per cell (6.0V across the leads of a six-cell pack). Then we'd ram a new charge into them at four to six amps to a temperature or voltage peak. Then repeat the cycle two or three times. It's _much_ better to do this sort of thing on the cells individually, but sometimes you have to improvise and do the pack as a whole. When you do the pack as a whole, you're only measuring the total (average) potential across the pack, and you can accidentally drive a cell into reversal, which can put it out of commission permanently. Anyway, with NiCds, a handful of cycles of very deep, controlled discharging followed by high-current charging to a voltage or temperature peak can recover the range of a cell or battery. It can also destroy it by causing it to vent. Some people are going to dispute what I've just said, including large-cranium-ed folks with degrees in various disciplines. That's OK. I've got the blown packs, the load-test traces, and the pack profile records to substantiate the effect I'm describing. Well, I probably should say that I _had_ them. They're somewhere in this compost heap I call a house, but I probably would need a month or two to put my hands on them. The difference between theory and practice? In theory there is none. In practice, there is. TTYL, DougF KG4LMZ
