Is it proper to multiply the mA rating x the number of batteries/cells?

like.. 2 1200 mA batteries would in theory take 12 hrs minimum?

Dave

Chris W wrote:
RobsSanta wrote:

My brain has totally gone blank for this simple question, I know I should
have paid more attention in school !!!.

I just was given a 12volt 1200mAh battery and a 200mh 3W wall charger
by a
friend who is quitting flying. It has been that long since he used the
battery he doesn't remember charging times etc.


For NiMH and NiCd, you take the battery capacity * 1.4 (I don't know
where the 1.4 came from I just read it somewhere) and then divide it by
the charge rate. That gives you the number of hours. So 1200 * 1.4 /
200 = 8.4 hours or 8 hours and 24 minutes. As others have said that is
assuming the charger "really" puts out 200ma. If you have a good volt
meter and can monitor the charge from time to time, when you slow charge
a NiMH or NiCd battery the fully charged voltage should be about
1.45V/cell while it is on the charger. This voltage will drop to
1.3V/cell or so shortly after the charger is removed. So what I would
do is record the voltage during charge every 20 or 30 min and if it
reaches 1.45V/cell stop charging. If it seems to plateau at a slightly
lower voltage then stop there.