RadioBanter - View Single Post - 15 Minute Rechargeable NIMH AA's 2000 Ah (Ray-O-Vac)

September 2nd 04, 04:42 PM

On 31 Aug 2004 21:26:14 -0700, (Grumpus) wrote:

snip
Also, the batteries become quite hot while charging (which I
understand is normal) so it is probably adviseable to let them cool
off before using them. The charger has a built in fan to help
dissipate the heat. Theoretically, these batteries are good for a
thousand cycles. Is the plastic charger up to the task when so much
force is required to insert the batteries?

snip

Assuming quality NiMh cells and each cycle is a full discharge (to
1V/cell) and then each recharge properly terminated (so they are
not overcharged) and at a standard rate of C/5 to C/10 (5-14
hours) at room temp, yes they could give about 1000 cycles of
gradually diminishing available power capacity -- down to about at
least 50% of the original when new. The internal resistace
builds up gradually as they age.

Being exothermic, a little heating (40C) is normal for NimH
towards the end of a charge. But when they get very hot during
charging the cycles and capacity will drop rather quickly.