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I have a couple of rechargeable AA NiMH batteries that I can no longer charge. After the charger claims the batteries have been charged fully they still output 0 Volt.

I found some posts that claim that batteries like this can be fixed by

  1. placing them in a freezer in a sealed plastic bag for 16-24 hours
  2. letting them warm up to room temperature
  3. Charging and discharging them a couple of times

Is this safe? Could this restore the batteries to "decent" working condition?

The question is meant to be generally useful but my specific batteries have the following specs: AA/HR6/DC1500 NiMH/1,2V/2300mAh.

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NiMH batteries can form dendrites internally that short out the battery. This is probably what is causing the symptoms you see. The usual way to deal with this is to discharge a big enough capacitor into the battery to blow out the dendrites.

However, if your batteries have been shorted for a significant time, which appears to be the case, they have been irreversibly damaged. These batteries shouldn't be discharged below about 900 or 800 mV. In your case they've been at 0 V for some time. Even if you could revive them, their capacity would be very low.

Ditch them and move on.

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  • 5
    \$\begingroup\$ He means "recycle them". ;^) \$\endgroup\$ – Transistor Dec 19 '15 at 13:37

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