Using the wrong charger?

What are the risks of using the wrong charger for rechargable batteries?  Can you do it if you don't leave the batteries on too long?  Can you get away with it if you make certain the batteries don't get too hot?  Specificially for my 18V power tools the charger I have is only intended to charge NiCad batteries.  The company that made the tools has also made different types of battery packs that are interchangable in the tools, but each battery pack comes with a different model charger.  What if I used the NiCad charger to recharge a NiMh battery pack?  What if I use the NiCad charger to recharge a Lion battery pack?

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Re-design5 years ago
I use the lithium batteries and they won't even plug into the old chargers. I doubt that the nimh batteries will either. Some people are selling old battery cases filled with nimh that will but I don't trust them.  Charging a nimh on the old charger will probably charge too fast.

In any case, the proper charger should be used for the battery you have. Batteries SHOULD NOT BE LEFT ON THE CHARGER LONGER than the time needed to recharge the battery.

My nicads lasted 4-5 years of heavy use because they were treated right even using the old charger. The new chargers are better but still the battery should not be left on charge too long.
Burf5 years ago
It depends on the charger type. An older type NiCad charger will usually charge an NiMh battery but it may undercharge it or take a very long time (like a couple of days) to fully charge. Less often, it may overcharge the battery and potentially cause a fire.
Unless the charger specifically states it will charge Li-Ion batteries, don't even try, it can destroy the Li-Ion batteries, and/or cause a fire or explosion.
If you have a newer DeWalt 18 volt charger as I do, they are "Smart Chargers," as are some others, and are backwards compatible with all three battery pack types. Just be sure to check the charger before you try.
etcmn (author)  Burf5 years ago
Unfortunately I have one of the first chargers made for the Ryobi +one. It is definately not a smart charger and even cooked the Ni-Cad batteries that originally came with it. They sell newer ones that are backward compatible but I can't afford to buy a new one. Don't mind if the NiMh batteries takes more than a full day to charge, just is there a way I can make sure they don't overcharge?
Burf etcmn5 years ago
Just keep an eye on the battery while charging. If it seems to be getting uncomfortably warm, remove it from the charger.