How to Rejuvenate an 18 Volt Cordless Battery

Written by james stevens
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How to Rejuvenate an 18 Volt Cordless Battery
Cordless power tools are great until the battery goes dead. (Electric drill with a drill on a white background image by terex from

Cordless power tools can be used almost anywhere: no worries about needing an electrical socket nearby or trying to find where you put your extension cable. Simply charge your 18V cordless battery for a few hours, put it in your power device and you're ready to go. It's all fine, until you find that your 18 volt cordless battery only lasts a few minutes, despite it being fully charged. If you find your cordless battery goes dead quickly then there's a simple, effective way of rejuvenating it.

Skill level:

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Things you need

  • 18 volt cordless battery charger

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  1. 1

    Put your 18 volt cordless battery in the charging unit. Turn on the charger and let it charge the battery until it's full. The light on the charger either illuminates to indicate it's full, or on some cordless battery chargers, a light is on while charging which turns off once the battery is fully charged.

  2. 2

    Turn off the charger. Remove the 18 volt cordless battery and insert it in the power device.

  3. 3

    Set the device to operate at its lowest power setting. You need to let the battery discharge as slowly as possible. Turn on the device and let it run. Wait until the device stops running.

  4. 4

    Turn off the device and wait 10 minutes so the battery and device cool. Turn on the device and you find that it starts running again. Leave it running until it stops then turn off the device. Wait 10 minutes.

  5. 5

    Repeat the process by turning the device on, letting it run until it stops and then turning it off. Eventually the device does not operate when you turn it on. The 18 volt cordless battery is fully discharged. Fully discharging the battery helps break down the chemicals in the battery cells and rejuvenates it.

  6. 6

    Put your battery into the charging unit once it's completely cool. Let it charge until full. You notice that it takes considerably longer than usual for the battery to charge. This is because the battery can now store much more energy. The longer it takes, the more rejuvenated your 18 volt cordless battery is.

Tips and warnings

  • If you find there's not much improvement after you have completed the procedure, repeat the steps a couple of more times. It can take two or three attempts to properly rejuvenate the battery.
  • If after completing the procedure several times the battery still doesn't retain a full charge then you need to get it replaced.

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