|Re: Is fast charging OK??|
Message #3 Posted by James M. Prange (Michigan) on 29 Apr 2007, 10:57 p.m.,
in response to message #2 by Dave Shaffer
I don't really know, but from what I've read, slow charging (as with a charger really designed for NiCd cells) is bad for NiMH cells. "Quick" charging (although I don't, offhand, know which rates) is supposed to be better for NiMH cells.
Also, if using a charger that charges 2 cells in series only, and 1 of the cells doesn't need as much charging as the other, then it will be over-charged, resulting in a shorter lifetime. Try to get a charger that charges each cell individually, especially when you're using an odd number of cells in a device, as in a 49g+. The best are supposed to be those that use a "negative Delta-V" method to determine when to switch to a trickle-charge mode or stop charging completely.
I really don't have that much experience with NiMH cells, but so far, the only problem that I've noticed (other than the self-discharge and relatively sharp drop at the end of the discharge curve) is that all of the NiMH AA and AAA cells that I have are slightly larger (longer, larger diameter, and corners not rounded as much) than is typical with ordinary alkaline cells, resulting in a tight fit in some devices.
I haven't tried the "hybrid" (NiMH + alkaline?) cells, but I've read that they're supposed to have a much slower self-discharge rate, but on the other hand, can be recharged maybe only half as many times as more conventional NiMH cells.
Regarding the rechargeable alkaline cells, specifically Rayovac Renewal cells, I was lucky with them (no damaged calculators), but note that they can't be successfully recharged all that many times, and worst of all, my experience was that after being recharged several times, they started leaking while in the charger. I decided not to use them any more.
Edited: 30 Apr 2007, 2:10 a.m.