How to check a battery for a dead cell

Written by james stevens
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How to check a battery for a dead cell
Use a voltmeter to check for a dead battery cell. (multimeter image by dinostock from

Rechargeable battery packs contain multiple cells. The cells are wired together in a series to give the battery greater voltage. If you find your battery goes dead quickly, or doesn't power your device properly, don't dispose of the battery pack: check the battery for a dead cell. One dead cell reduces the battery's energy capacity. It's considerably cheaper to replace a dead cell than to purchase a new battery pack.

Skill level:

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Things you need

  • Battery charger
  • Screwdriver
  • Voltmeter

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  1. 1

    Charge your battery using the battery charger until it's full. Once it's full, unplug the charger and leave the battery for several hours; overnight is best. Good cells retain their charge while bad cells go dead.

  2. 2

    Remove the battery cover. Either remove the small screws using a screwdriver, or undo the clips that hold the cover in place. They are usually hinged clips, so insert a screwdriver under the clip and lever the hinge open. The battery cells are visible.

  3. 3

    Read the voltage output on the cells. Battery cells produce 1.2 volts or 3.7 volts.

  4. 4

    Place your voltmeter near the battery. Use the two wires from the voltmeter to touch the negative and positive terminal of a battery cell. The wires are coloured red and black, indicating positive and negative. The battery terminal are clearly labelled with "+" and "-" markings.

  5. 5

    Read the cell output on the voltmeter. It reads 1.2 volts or 3.7 volts, depending on the type of cell. If it reads less than 1 volt for a 1.2-volt cell or less than 3.4 volts for a 3.7-volt cell, the cell is dead and needs replacing.

  6. 6

    Repeat the process on all the battery cells. Mark bad cells with a marker so you know the ones to replace.

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