NiMH batteries use a Nickel Metal Hydride cell to deliver power to electronic devices. Unlike standard batteries, NiMH batteries can be recharged and used repeatedly once they have ran out of power. However, NiMH batteries can experience certain conditions that force them to loose their recharging capabilities. While some batteries are beyond repair and will not come back from the dead, there are a couple steps you can take to bring your AA NiMH battery back to life.
Place your dead NiMH batteries in the plastic bag and put them in your freezer. Let the batteries sit in the cold for 3-4 hours.
Place the battery in the discharger and let it deplete the battery completely.
Insert the battery into the charger as soon as it is depleted and wait overnight or until it has reached a full charge.
Put the battery back into the freezer and let it sit for another couple of hours.
Remove the battery from the freezer and place it on the discharger. Let it run completely out of power before placing it back on the charger. Charge the battery until it is full, place it in the freezer and repeat the process.
Continue repeating the process until the battery is restored; ideally this will take about 5-7 times. Perform the process to supplement the strength of the battery.
Not all dead NiMH batteries can be restored, especially if they have experienced some form of physical damage.