Re: Can't Recharge Rechargeable Batteries?

powrwrap@xxxxxxx writes:

I bought a LaCrosse BC-900 battery charger last February. It came with
four rechargeable AA batteries. At the time, I charged these batteries
up and put them I put four of the batteries in one of those
self-contained video game joysticks to plugs into your TV. Eventually
after playing the game for several days (weeks?) the game would start
up and then crap out. I inserted them in the charger and three of the
four batteries gave the reading of "null" and couldn't be recharged.
LaCrosse replaced them but warned me that I had let them drain down too
far. I couldn't understand how, since the game would power up and then
"die" after about 5 to 10 seconds.

To protect rechargeable batteries, any electronic device that uses 4 of
them needs to shut itself down completely when the voltage drops to
about 4 V (normal operating voltage from 4 cells is 4.8 V). If it
continues drawing current beyond this point, it can drive some of the
cells down to zero volts and then into reverse charge, which is a good
way to kill them. If the game has a real mechanical power switch, it
shouldn't do this, but if it has some sort of "soft" power button then
it's probably drawing current from the batteries 24 hours/day.

I went out and bought twelve Energizer 2500 mAh nickel metal hydride
batteries. Have been using them in my camera and in the wife's portable
CD player. I put four of them in the TV game back around Easter and now
three of the four of them give the reading "Null" when placed in the
charger and apparently can't be recharged.

Or can they? Does anybody know if these batteries can be brought back
to life?

A voltmeter shows 0.06 volts or so on these cells.

It could be that the batteries are just fully discharged, and the
LaCrosse charger won't try charging them because it's cautious. Or
the cells could be shorted. If you have an old slow battery charger
(NiCd or NiMH), put the cells into it and let them trickle charge for
perhaps 10 minutes, then measure the voltage again. If they are now
above 1 V, the cells are probably recoverable, and the LaCross will
probably now charge them. If they're still around 0 V, they're shorted.

In an emergency, you could clear the short with a pulse of high current
and then recharge the cells, but their life is not likely to be long
after that. They're cheap enough that when they're shorted, just
discard them.

Dave
.