GoKawiilExplainer: effects of a dead CMOS battery on desktop PCs
A failing CMOS battery, typically a CR2032 or CR2025 coin cell, loses its ability to keep a motherboard's clock and BIOS/UEFI settings intact when the system is unplugged. Symptoms include the date resetting to a default like January 1, 2000, boot-time warnings, and BIOS settings such as boot order reverting to factory defaults. Replacing the battery is cheap and simple, and using sleep mode instead of rebooting can temporarily preserve settings on a dead battery.
GoKawiil's interpretation of the reporting above, not reported fact.
An incorrect system date can cause practical problems beyond annoyance, such as HTTPS websites failing to load because security certificates depend on accurate time. Many modern operating systems mask early symptoms by fetching time online, which could mean users don't notice a dying battery until BIOS settings are fully reset. The issue mainly affects desktops, since most laptops rely on their main battery rather than a dedicated CMOS cell for timekeeping.
- CMOS batteries, usually CR2032 coin cells, power a motherboard's clock and BIOS memory when unplugged.
- A dead battery resets BIOS/UEFI settings to factory defaults and can cause date errors affecting HTTPS sites.
- Desktops are more prone to this issue than laptops, which often use their main battery for the clock instead.
Energizer CR2032 Lithium Batteries — If your PC's clock keeps resetting to 1970, a fresh CR2032 coin cell is the cheap fix that solves it instantly. These are the same standard batteries used in motherboards and AirTags, so keeping a few on hand means you're never caught without one when your CMOS battery finally dies.
See Energizer CR2032 Lithium Batteries on Amazon → Affiliate link — we may earn a commission on purchases, at no extra cost to you. Product picked by AI based on this article; it is not a tested recommendation.Source: engadget.com — Calvin Wankhede, 2026-10-26
Published there as: “What happens when your PC's CMOS battery dies?”
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