NiMH batteries are a type of rechargeable battery. They generally come in AA size but can sometimes come in smaller and larger sizes. They have uses ranging from digital cameras and remotes to wireless video game controllers and other portable electronics. Often they are used to replace disposable one-time use alkaline batteries, allowing the user to reuse the NiMH battery over and over again. Over time the batteries will lose their original charging capacity and eventually cease to function. Testing them determines if you need to replace them.

 

Remove the NiMH batteries from the device they are in. Most devices have a battery compartment that opens by a sliding door or hinged door.

 

Insert the batteries into the NiMH battery charger. Plug the battery charger into a wall outlet. Allow the batteries to charge for up to five hours. It is important to not overcharge NiMH batteries as this can shorten their lifespan.

 

Remove the batteries from the charger and reinsert them into the device. Turn on the device and use it normally. If the device powers on and is usable, the batteries are still working.

 

Note the amount of time of normal use it takes for the batteries to drain. Over time and after hundreds of recharge and discharge cycles, the NiMH batteries lose their full charge capacity. Also, if the batteries fail to hold a charge for more than a few minutes, then they are no longer usable.