Medion MD41500 CMOS Battery 3V 200mAh Lithium Coin Cell

Medion MD41500 / MD41300 / MD41567 — 3V Lithium CMOS Backup Battery

This is a 3V 200mAh lithium coin cell that replaces the CMOS backup battery on Medion MD41500, MD41300, and MD41567 motherboards. It powers the RTC circuit and SRAM that hold your BIOS settings when mains power is disconnected. Without a functioning cell, the board loses its clock and configuration every time the plug comes out.

• MD41500, MD41300, MD41567 compatibility: All three boards share the same coin cell socket geometry and 3V retention circuit. The CMOS SRAM on each draws from this cell continuously — even when the system is off — to preserve BIOS settings and keep the real-time clock ticking.
• Bench tested on actual hardware: We measured open-circuit voltage on cells from this batch before dispatch. Every cell read above 3.0V under no-load and held retention voltage above the 2.8V CMOS minimum under a simulated RTC draw.
• After-install clock correction: After fitting the new cell, enter BIOS immediately and set the correct date and time, then save and exit. The RTC circuit resets to a default value — often 1 January 2000 — after any cell swap, and the board will not correct this automatically.

BIOS clock resetting to 2000 after every power cycle

When the CMOS cell drops below 2.8V, the RTC circuit loses its reference voltage and resets to the factory default date — typically 1 January 2000 — on every cold boot. The board may still POST and boot normally, masking the fault until you check the system clock. A cell reading below 2.8V on a multimeter confirms the cause. Replace the coin cell, then set the correct date and time in BIOS and save before exiting.

CMOS checksum error on boot after fitting a new coin cell

A checksum error immediately after a cell swap usually means the BIOS compared stored settings against a now-blank CMOS and found them mismatched — not a fault with the new cell itself. This happens because removing the old cell erased the SRAM contents entirely. Enter BIOS setup, load the optimised defaults, set your date and time, then save and exit to write a valid checksum and clear the error.