How to Fix a Computer Stuck in a CMOS Battery Reset Loop

Published 2026-10-16 · LuxuriousComputers Repair

Every time you turn on your computer, the date and time are wrong, the BIOS settings have reverted to defaults, or you see an error message like CMOS Checksum Error, CMOS Battery Failure, or System Time Not Set. You fix the settings and they hold until you shut down or unplug the computer — then the next boot resets everything again. This is a CMOS battery problem. The CMOS battery is a small coin-cell battery on the motherboard that keeps the BIOS settings and real-time clock running when the computer is powered off.

What the CMOS battery does

The CMOS battery (usually a CR2032 lithium coin cell) powers a small amount of memory (CMOS RAM) on the motherboard that stores BIOS/UEFI settings — boot order, hardware configuration, date and time, overclocking profiles, fan curves, and other parameters you configure in the BIOS setup. When the computer is plugged in and on, the motherboard powers this memory from the power supply. When the computer is off or unplugged, the CMOS battery takes over. A dead or dying battery means these settings are lost every time power is removed.

Symptoms of a failing CMOS battery

• Date and time reset: The most obvious symptom. The clock resets to a date in the past (often the motherboard's manufacture date or January 1 of some year) every time the computer starts. This causes certificate errors in web browsers, failed software license checks, and incorrect file timestamps
• BIOS settings reset: Custom settings like boot order, fan profiles, RAM speed (XMP/DOCP), and hardware configurations revert to factory defaults on every boot
• CMOS Checksum Error: A message at boot saying the CMOS checksum does not match, meaning the stored settings have been corrupted because the battery could not maintain them
• Press F1 to continue: The computer pauses at boot asking you to press F1 to enter setup or F2 to load defaults, because it detected the settings have been reset
• Boot order problems: If the BIOS resets the boot order to defaults, the computer may try to boot from the wrong drive, show No Boot Device Found, or boot into the wrong operating system on dual-boot setups
• Computer will not start at all: In rare cases, a completely dead CMOS battery can prevent the computer from completing POST (Power-On Self-Test), though most modern motherboards will boot with a dead battery using default settings

Replace the CMOS battery

Replacing the CMOS battery is the fix for 95 percent of CMOS reset loop problems. It is one of the simplest hardware repairs:

Desktop computers

1. Shut down the computer and unplug the power cable. Press the power button once after unplugging to discharge any remaining power
2. Open the side panel of the case
3. Locate the CMOS battery on the motherboard. It is a silver coin-shaped battery about the size of a quarter (20mm diameter), sitting in a small holder on the motherboard. On most motherboards it is easy to spot. On some it may be near the graphics card slot or partially hidden by cables
4. Note the orientation of the battery — the positive (+) side faces up on most motherboards
5. Release the retention clip holding the battery. There is usually a small metal tab that you push to the side, and the battery pops up
6. Insert the new battery (CR2032, available at any pharmacy, grocery store, or electronics store) in the same orientation — positive side up
7. Close the case, plug in, and power on. Enter the BIOS (press Delete, F2, or the key shown at boot) and set the correct date, time, and any custom settings. Save and exit. The settings should now persist across power cycles

Laptop computers

Laptop CMOS batteries are less accessible:

• Some laptops use a standard CR2032 in a holder accessible from the bottom panel
• Others use a smaller coin cell (CR2016 or CR1220) or a battery connected with a wire and plug to the motherboard. The wired type looks like a small flat disc attached to two thin wires with a small white connector
• On many modern thin laptops, the CMOS function is handled by the main battery. If the main battery is completely drained (0 percent for an extended period), CMOS settings can be lost. Charging the main battery resolves this without replacing a separate CMOS battery
• Check your laptop model's service manual for the CMOS battery location and type before opening the laptop

After replacing the battery

After installing a new CMOS battery, you need to reconfigure some settings:

• Date and time: Set the correct date and time in the BIOS. Windows and Linux will also correct the time automatically once they boot and sync with an internet time server, but the BIOS time affects early boot behavior
• Boot order: If you changed the default boot order (for example, to boot from an SSD instead of a hard drive, or to prioritize a specific drive), reconfigure this in the BIOS
• XMP/DOCP: If you had enabled XMP (Intel) or DOCP (AMD) to run RAM at its rated speed, re-enable it in the BIOS. After a CMOS reset, RAM runs at its default (slower) speed
• Fan profiles: Custom fan curves or quiet mode settings need to be reconfigured
• Secure Boot and TPM: If your system uses Secure Boot or TPM for BitLocker or other security features, verify these settings are correct. A CMOS reset may disable Secure Boot, which can prevent Windows from booting if BitLocker is enabled

Battery keeps dying quickly

If you replace the CMOS battery and it dies again within weeks or months instead of the normal 3 to 5 year lifespan:

• Computer is unplugged for long periods: If the computer sits unplugged for weeks at a time, the CMOS battery drains faster because it is the sole power source for the CMOS memory with no help from the power supply. Leaving the computer plugged in (even when off) extends CMOS battery life significantly because the standby power from the PSU supplements the battery
• Motherboard power drain: Some motherboard components draw excessive standby power from the CMOS battery circuit. This is rare but can happen with defective voltage regulators or other component failures. If the battery drains abnormally fast and the computer is normally plugged in, the motherboard may have a fault
• Bad replacement battery: Cheap or old-stock CR2032 batteries may already be partially drained. Buy a fresh battery from a reputable brand (Energizer, Duracell, Panasonic). Check the expiration date on the packaging

CMOS reset without battery replacement

If you cannot replace the battery immediately but need to stop the reset loop temporarily:

• Enter the BIOS, set all required settings, save, and leave the computer plugged in and powered on (or at least plugged in with the power supply switch on). As long as the power supply provides standby power, the CMOS settings are maintained
• Some motherboards have a CMOS jumper or button that can clear the CMOS. Make sure this jumper is in the normal position (not the clear position) — if it was accidentally moved to the clear position, the CMOS resets every boot regardless of battery health

CMOS jumper check

Before buying a new battery, check the CMOS clear jumper on the motherboard:

• The CMOS clear jumper is usually a 3-pin header near the CMOS battery, labeled CLR_CMOS, JBAT1, or similar
• Normally, the jumper cap sits on pins 1-2. If it is on pins 2-3, the CMOS is in clear mode and will reset on every boot
• If the jumper was moved accidentally during work inside the case, or if a tool touched the pins and bridged them, the CMOS clears on every boot even with a perfectly good battery
• Move the jumper to the normal position (consult your motherboard manual for which pins) and test

CMOS battery repair in Columbus or Delaware

If your computer keeps losing its BIOS settings, date, and time, LuxuriousComputers can replace the CMOS battery, check the motherboard for excessive drain, reconfigure your BIOS settings after replacement, and verify the fix holds across power cycles.