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What battery does a computer motherboard (CMOS / BIOS) use?
Most computer motherboards (CMOS / BIOS) take a CR2032 (3 V lithium coin cell). Some use CR2025 instead. The coin cell sits in a round holder on the motherboard; switch the PC off and unplug it before removing it.
| Battery | How common | Size | Volts | Capacity |
|---|---|---|---|---|
| CR2032 | Most common | 20 mm × 3.2 mm | 3 V | ≈ 225 mAh |
| CR2025 | Also used | 20 mm × 2.5 mm | 3 V | ≈ 165 mAh |
Computer Motherboard (CMOS) battery: what to know
- Almost all desktop motherboards use a CR2032 to keep the clock and BIOS settings while the PC is unplugged.
- A dying CMOS battery shows up as the date and time resetting, or BIOS settings being lost after power cuts.
- Many laptops use a coin cell with a wire lead and plug instead of a loose CR2032; buy the matching part for the laptop model.
How to check which battery your computer motherboard (CMOS / BIOS) takes
The coin cell sits in a round holder on the motherboard; switch the PC off and unplug it before removing it. Battery codes are printed on the flat face of coin and button cells and along the side of AA, AAA and 9V batteries. Match the code exactly: a CR2025 or CR2016 is the same width but thinner, and a CR2450 will not fit.