ray said:
I have a flashlight handle that uses 2 1700 mAH Nimh batteries in
series.
How strong of an unregulated ac/dc wall transformer can I use safely
to recharge the handle?
It must be safe to leave plugged in for days at a time.
Will a 3vdc 200 mAH output transformer overheat the batteries or cause
damage?
Should I stay at 100 mAH to be safe?
What is the strongest transformer I can use?
It's generally bad to leave batteries on continuous charge. The reason
you see it done so much is because it's cheap, and the vendor doesn't
care if your batteries last a long time.
Rechargeable batteries in a flashlight are problematic because the
voltage drops off suddenly. If the cells aren't perfectly balanced,
the weak one will go into reverse charge rather quickly. That weakens
it further and the whole thing snowballs. Turn it off at the first
sign of light dimming.
If you use it heavily sometimes and none other times, you have a
problem. You need a better method of charge control. If you use it
rarely, you should look into using the SMALLEST, not the largest current
that will keep it up...remembering that it's still bad.
I've put my rarely used items on a timer. I charge them half an hour
per day at a rate that just puts back the self-discharge plus average
use...which is typically zero. Had fewer battery failures since.
mike
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