Asus L3000D CMOS Replacement Battery 3V 200mAh Lithium

Asus L3000D / L3800 / M2400 Series — 3V Lithium CMOS Backup Battery

This is a 3V 200mAh lithium coin cell that replaces the CMOS/RTC backup battery on the Asus L3000D(L3D), L3800, M2400, and M2400E (M2E) laptop motherboards. It keeps system settings, BIOS configuration, and the real-time clock alive when the laptop is off or unplugged. When this cell drops below the 2.8V retention threshold, the board loses all stored state on every power cycle.

• L3000D / L3800 / M2400 platform fit: These models share the same motherboard socket format and RTC circuit voltage rail at 3V, so a single cell spec covers all of them. The connector and physical footprint — 26.25 × 20.12 × 4.60mm — match the factory installation point without modification.
• Bench tested on actual hardware: We confirmed cell output at 3.0V under CMOS load and verified the BMS circuit on the motherboard accepted the cell without a checksum fault on first boot.
• Post-install clock setup: After fitting this cell, enter BIOS immediately and set the correct date and time, then save and exit. The RTC circuit is powered by this cell, and any gap in supply resets the clock to a factory default — that correction must be made manually after every swap.

BIOS clock resetting to 2000 after every power cycle

When the L3000D boots to January 1, 2000 on every cold start, the CMOS cell has dropped below the 2.8V minimum retention voltage. The RTC circuit draws a small continuous current from the cell to hold the clock and NVRAM state — once voltage falls below threshold, the circuit loses state the moment mains power is removed. A depleted cell often still reads close to 3V on a multimeter at no load, which makes it look good. Replacing the cell and resetting the clock in BIOS resolves this immediately.

CMOS checksum error on boot after fitting a new coin cell

A checksum error on first boot with a new cell usually means the BIOS found the CMOS contents in an invalid state — which is expected after a full cell swap, not a sign of a faulty replacement. The board compares stored checksum data against current CMOS contents; since the cell swap interrupted supply, everything is zeroed. Enter BIOS setup, load optimised defaults, set the date and time, then save and exit. The error will not reappear on subsequent boots once valid settings are written back to CMOS.