How to refresh nimh batteries

Written by sarah coennen
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How to refresh nimh batteries
(digital multimeter 3 image by dinostock from

NiMH batteries, or nickel metal-hydride batteries are one of the most renowned rechargeable batteries on the market today, because they are said to outlast most other rechargeable batteries. They are also beneficial for the environment because of their charging capabilities. You can get over 1,000 uses out of these batteries if you take care of them properly. The batteries might need a quick refresher, especially if they have been in storage for awhile, so they will properly hold a charge.

Skill level:

Things you need

  • AC adaptor
  • Digital multimeter
  • Battery charger
  • Electrical socket

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  1. 1

    Use the digital multimeter as described in the instruction manual to test the voltage of each battery you wish to refresh.

  2. 2

    Make sure the voltage reads 1.0 volt or lower for each cell. If the voltage is 1.2 volts per cell, then the battery just needs to be charged.

  3. 3

    Touch the red cable alligator clip of the AC adaptor to the positive end of the battery.

  4. 4

    Touch the black cable alligator clip of the AC adaptor to the negative end of the battery.

  5. 5

    Hold for three seconds.

  6. 6

    Take the AC adaptor away from the battery.

  7. 7

    Test the voltage again with the digital multimeter. If the voltage is the same, repeat this process again. Sometimes it takes two or three shockings to revive a battery. If the voltage is still the same after trying this process three times, the battery needs to be replaced. The voltage should rise to only 1.2 volts per cell after shocking.

  8. 8

    Let the batteries rest for 10 to 15 minutes before attempting to use them. If the batteries are not working, charge them as usual with the battery charger.

Tips and warnings

  • You can buy all the equipment you need at tool supply and electronics stores, as well as online and through tool catalogues. If the battery casings are damaged, be safe and throw them away.

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