Rechargeable batteries are conducive with a green standard of living that has taken the world by storm. These batteries are low maintenance with the proper care, but a little more care may be needed for batteries that have been stored for a long time, or batteries that have not been properly cared for.
Put the batteries into the electronic device and try to turn it on. If the device turns on, then let the device remain on until the batteries are fully dead. If the device does not turn on, take the batteries out and proceed to the next step.
Test the voltage with the digital multimeter by placing the cable ends to the corresponding polar end of the battery. The voltage should read 1.0 volts or lower for each cell.
Charge each battery with the AC adaptor and pay attention to the polarities. Failure to do so can permanently damage the battery and render them useless. Do not charge for more 3 seconds for each battery.
Check the voltage again with the digital multimeter. It should read 1.2 volts per cell. If not, repeat this process. If the voltage is still less than 1.2 volts per cell, discard the battery.
You can purchase AC adaptors and digital multimeters from any tool supply store.
Do not attempt to charge batteries in chargers that are not specific to your type of rechargeable battery (NiMH, NiCd, Li-ion, Alkaline, etc.), or batteries with broken or cracked casings. This may result in explosion and/or serious injury.