Acer Aspire 6920 CMOS Battery 02k6486 3V 200mAh Lithium

Acer Aspire 6920 / 8920 Series — 3V Lithium CMOS Backup Battery (02k6486)

This is the CMOS coin cell for the Acer Aspire 6920, 6920G, 8920, and 8930G motherboards. It runs at 3V with a 200mAh (0.6Wh) capacity and powers the RTC circuit and SRAM that stores BIOS settings while the laptop is off. When this cell drops below retention voltage, the board loses the clock and all saved BIOS configuration on every power cycle.

• Aspire 6920 and 8920 platform fit: These models share the same OEM part number 02k6486 because they use the same motherboard CMOS circuit — identical voltage rail, connector footprint, and retention spec. One cell covers all variants in both series.
• Bench tested on actual hardware: We verified open-circuit voltage at or above 3.0V before shipping. The cell holds a stable charge under the low-current draw typical of RTC and SRAM retention circuits.
• Post-install clock correction: After fitting this cell, enter the BIOS immediately and set the correct date and time, then save and exit. The RTC circuit resets to a default date on every install — the new cell holds whatever value you write to it, but it cannot pre-populate that value on its own.

BIOS clock resetting to 2000 after every power cycle

The RTC circuit on these Aspire boards requires at least 2.8V from the CMOS cell to retain the clock value when mains power is removed. A depleted cell may still show enough voltage to POST normally but cannot sustain retention voltage through a full power-off cycle. The result is the clock snapping back to a default date — often 1 January 2000 — every time you unplug or shut down. Replacing the cell and writing the correct time in BIOS resolves this; the minimum retention threshold is 2.8V.

CMOS checksum error appears on boot screen

A checksum error means the BIOS has compared stored settings against its checksum value and found a mismatch — which happens when the CMOS cell is fully depleted and SRAM contents have corrupted or cleared. This is a different symptom from a drifting clock: the board is flagging that saved configuration data is no longer intact, not just that the time is wrong. After fitting the replacement cell, enter BIOS setup, reload defaults, re-enter any custom settings, and save. If the error reappears after a fresh cell is installed, check that the battery contact spring is clean and seated — an oxidised spring can prevent the cell from making reliable contact.