If your laptop has a dead CMOS battery and the OEM no longer sells new CMOS batteries (and aftermarket ones are hard to find), it is possible to take the dead battery apart and replace the cell so your laptop holds the CMOS contents again.

Note: This procedure is only recommended for older notebooks. If a replacement with leads is available, it's better to buy a pre-assembled battery. This approach is somewhat error-prone.

Guide notes:

  • The cell does not need to be 100% covered. However, every visible area of the cell must be protected. Liquid electrical tape is used to do this since it can be removed if something goes wrong.
  • Disassembly of your laptop is not covered. Every laptop is different, so research the disassembly procedure specific to your laptop.
  • This guide ONLY applies to coin cell rebuilds. Do not use this guide for other style batteries.
  • When adding tape to the cell, do not create a direct short. To avoid this, place the tabs slightly higher than the factory placement and cut the tape sorter then you need.
  1. Most laptops use a CR2016/2032 cell.
    • Most laptops use a CR2016/2032 cell.

    • Take the battery apart and check out what cell you need. Depending on how it is built, the wrapping may be difficult to remove.

  2. Use caution doing this. If you break the leads, you may need to purchase a new battery.
    • Use caution doing this. If you break the leads, you may need to purchase a new battery.

    • After purchasing a battery, disassemble the CMOS battery. Use caution not to bend the tabs a lot. Too much damage may make them unusable.

    • Break the tabs off of the old battery. Discard or recyle the old battery depending on your state's laws.

    • Do not use too much tape. This may short out the cell and cause it to explode!

    • After the polarity has been matched, tape the leads to the new cell. Do this for both sides. Start on the + side and cut the tape to fit comfortably. Doing this side now greatly reduces the risk of error.

    • To place the negative tab safely, try and keep it as close as possible to this example image.

    • Perfect coverage is not required. As long as most of the cell is covered, you are okay.

    • After verifying both leads are securely held onto the new cell, apply liquid electrical tape to the battery. 2 thin coats are recommended. If applied thick, only use one.


After building the replacement cell, install it in the notebook. Verify the battery works by setting the BIOS, powering it off and then removing the battery/AC adapter. If the CMOS memory is retained, your battery works.


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