matt weber wrote:

First of all it isn't 4 x 1300mah, the batteries are charged in
series. Figure the charginig process isn't 100% efficient, so you
need to charger to about 120% of capacity, however you rarely run the
batteries flat. Long term overchargiing converts water to oxygen and
hydrogen which are vented from the battery, resulting in battery
failure.

I was under the impression that Potassium Hydroxide was the electrolyte
being used, not water...I may be wrong.

You need to estimate how far down you are going to run the
battery, Without knowing how it evaluates battery charge, it is hard
to know what 25% really represents. NiCd and NiMh have pretty flat
discharge characteristics, so at the point at which you notice a
significant voltage drop, the battery is pretty much flat

It is better to think the NiMh batteries have a rapid discharge rate and
a flat 'running' range. They hold their rated voltage longer than a lead
acid, but near the end of the capacity, suddenly drop. That is why they
are a bad idea for smoke detectors. You might not be around when they
give the warning beeps.

nimh discharge:

http://snipurl.com/z3f3

Dry cell types have a longer slope of discharge and it starts WAY
earlier in the charge life of the battery. They give you lots of warning
as they approach an inoperative state.




mike