Can I substitute a NiMH battery for NiCd in a cordless phone?

Alright, I'm definitely sticking with the NiCd. ;-)

:I recently bought a cordless phone, which came with a NiCd battery. In the :manual it says: : :"To reduce the risk of fire, use only 3.6V 850mAh Nickel :Cadmium (Ni-Cad) cordless telephone replacement :battery pack." : :I've heard about the dreaded "memory effect" with NiCd batteries, so I'm :interested in replacing it with a NiMH one. Someone who is selling a 3.6V :1000mAH NiMH battery on Ebay claims it works with my phone, but will it really :be safe? Wouldn't want to install a NiMH battery and have the house burn :down. My oldest cordless phone is still going strong, and I feel strongly that it has NiCads, although I'm not certain. It must be around 7-8 years old or more. I always leave the thing charging.

My other cell phones have been a different story. I have a Panasonic, that replaced (by RMA) a previous version of the same phone, and they have NiMH's. Both of these phone's manuals suggest not leaving the packs charging for maximum battery life, which is certainly a PITA. It's much easier to just leave it charging, since the base has to be plugged in regardless for the phone to work. However, in deference to that admonition I've not kept it charging but the first battery pack died in less than a year in any case. The newer one is still alive after maybe

I'd seriously suggest just using the NiCads in this phone of yours and if and when they die, then think about replacing them, not sooner.

NiMH's do not like trickle charge, see ..

and this is what happens in most simple devices like phones etc.

/WK

I don't know where Panasonic is coming from on this, but most battery manufacturers are OK with trickle charging, indeed most of the cycle-life tests are done with a 13 to 16 hour trickle charge.

It might be that Panasonic is trying to cover up for the fact that NiMH cells _do_ have "memory" and are trying to keep people from seeing it.

Leaving the packs on a C/10 trickle charge for weeks on end will cause a voltage depression "memory" effect just like NiCads.

The oxygen recycling mechanism from NiCads works just as good or better with NiMH, trickle charging is OK.

Best regards mark

Wolfgang Kern wrote:

Agreed.

Jim

| I don't know where Panasonic is coming from on this, but most | battery manufacturers are OK with trickle charging, indeed | most of the cycle-life tests are done with a 13 to 16 hour | trickle charge. | | It might be that Panasonic is trying to cover up for the fact | that NiMH cells _do_ have "memory" and are trying to keep people | from seeing it. | | Leaving the packs on a C/10 trickle charge for weeks on end will | cause a voltage depression "memory" effect just like NiCads. | | The oxygen recycling mechanism from NiCads works just as good or | better with NiMH, trickle charging is OK.

C/10 is not a trickle charge -- it's much faster than a tricke charge.

It's a slow charge, mind you, but a trickle charge is a good deal slower.

Lots of people do seem to confuse C/10 with a trickle charge, however.

A `trickle charge' is defined as `An electric charge supplied to a storage battery at a continuous low rate to keep it fully charged' and for a NiMH cell that's probably around C/50, and for a NiCd it's even slower.

Neither NiCd nor NiMH cells like being charged at C/10 day in and day out. They may last a few months, and the NiCd cells will suffer voltage depression (which is often mistakenly called `memory') and I suspect that the NiMH cells will do, but to a lesser degree. But a few days of C/10 won't hurt it, and in fact about 20 hours of C/10 is pretty important for `forming' a NiCd or NiMH cell when it's brand new.

I agree with everything you say, but a lot of people call the C/10 charge a trickle charge. Right or wrong, jargon isn't locked down.

Best regards mark

Doug McLaren wrote:

quoting

ecautions.pdf

Though the ready made NiMh cardless packs are spec'd for this kind of service. They can take constant trickle charging much better than standard batteries. So as long as the OP gets one of these, he'll be ok.

There is always a trade off. The trade off with these batteries is lower capacity than standard NiMh. Just look at the capacity: The lower capacity is a dead give away, though it's still more than double than a standard NiCad pack.

It's about 2 years since I replaced the NiCd pack in my cordless phone handset with NiMH. No problems so far. The phone is one of the older types and probably about 6 years old.