CMOS Battery

Category: infrastructure

A small battery on the motherboard that powers the BIOS/UEFI settings even when the PC is unplugged.

The CMOS battery is the "memory backup." It stores the time, date, and hardware settings. If your PC suddenly forgets the date or keeps asking you to "Press F1 to Load BIOS Defaults" on every boot, your CMOS battery is dead and needs a replacement.

Common Examples

• Replacing the CR2032 CMOS battery on the motherboard fixed the recurring system-clock error we saw on every startup.
• The CMOS battery ensures that your BIOS configurations are retained even during long periods of total power loss to the system.