General Question

Jbor's avatar

Can I replace Nickel Cadmium batteries with NiMH?

Asked by Jbor (649 points ) January 14th, 2009

I’m trying to replace the internal rechargable batteries in a shaver. The ones used are two AA 600mAH Nickel Cadmium, an the ones I have lying around are NiMH 2100mAH (have some 1200 as well). All are 1.2V. Would that work?

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7 Answers

robmandu's avatar

Yah, that’s fine.

Just don’t put your NiMH batteries in the NiCad charger.

Jbor's avatar

That’s the problem, the charger is internal, so it’ll have to use the same. What would (or could) the consquences be?

robmandu's avatar

Hmmm… googling a bit and it looks like that there do exist chargers that can handle both battery types.

http://bit.ly/g1pP

OTOH, since you’re talking about an integrated charger in a device purposed for something else, I’d tend to err on the side that it won’t handle NiMH properly.

Got an owner’s manual? Maybe it can provide guidance?

Jbor's avatar

I’ve been googling as well:
http://en.wikipedia.org/wiki/Nickel-cadmium_battery
http://en.wikipedia.org/wiki/Nickel_metal_hydride_battery

The charger has a cutoff already, but I’m unsure as to whether it will work with NiMH.

Jbor's avatar

That was an excellent link, by the way.

“Many of the older NiCd chargers are the simple timed type charger which will charge batteries for a fixed amount of time and then shut off. Unfortunately, since NiCd batteries have a much lower capacity than NiMH batteries, the timer is likely to shut off long before the NiMH batteries are fully charged. This won’t harm the batteries, but the NiMH batteries won’t be fully charged since the timer will have stopped the charge cycle too soon.”

“Also common among older NiCd chargers are the so called “overnight” chargers which charge batteries at a low rate as long as the charger is plugged in. This type of charger can fully charge NiMH batteries, but it might take a very long time to do so. It’s possible that an old NiCd charger could take as long as 48 hours to fully charge new high capacity NiMH batteries! This type of charger is not likely to damage NiMH batteries unless the batteries are left in the charger for weeks at a time, but it may not be very convenient to use. If you have this type of charger you can get an idea of how long you’ll need to charge your batteries by using the calculator found above. ”

I think I’ll give it a go :-)

robmandu's avatar

G’luck, muchacho!

Jbor's avatar

NiMH turned out to be ill suited for the job. They just cannot deliver the energy fast enough. I bought a couple of 850mAH NiCD batteries for around 9$ delivered, and it works great now.

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