On Jan 17 2005, 17:06, Paul Koning wrote: <shoppa_classiccmp(a)trailing-edge.com> writes: of Lead-acid, lithium, various others, and NiMH/NiCd certainly need very different charging regimes, but NiMH and NiCd are very similar to each other. The most important difference is that for a NiMH you should stop the charging when the voltage flattens out, and before it starts to fall again; for a NiCd you should stop when the voltage just starts to fall again. Of course, you shouldn't let them get too hot, and you shouldn't fast-charge very cold batteries either. Maxim do a couple of inexpensive chips (MAX712/MAX713) that take the hard work out of all that; used with a thermistor, they won't fast-charge cold cells until they warm up, and they won't fast-charge until the cell voltage rises above some threshold. I've used them but I've not put enough cycles through enough cells to see what the life is like. Interestingly, Maxim's data sheet indicates that the difference between detecting the voltage slope flattening and detecting the slight fall is less important to NiMH cells, especially when the charge rate is fairly *high*. That means for a lot of applications you could safely use an NiCd charger for NiMH cells, but vice-versa would leave you with slighly undercharged NiCds. -- Pete Peter Turnbull Network Manager University of York