Evesham Voyager C720DC CMOS Replacement Battery 3V 200mAh

Evesham Voyager C720DC — 3V Lithium CMOS Replacement Battery

This is a 3V 200mAh lithium coin cell that replaces the CMOS battery on the Evesham Voyager C720DC motherboard. It powers the real-time clock (RTC) circuit and retains BIOS settings when mains power is removed. When the original cell drops below its minimum retention voltage, the board loses date, time, and firmware configuration on every power cycle.

• Voyager C720DC RTC circuit: The C720DC motherboard uses this coin cell to back the SRAM and RTC registers continuously. The cell supplies the RTC rail independently of the PSU, so a depleted cell means all settings vanish the moment the mains plug is pulled.
• Bench tested on actual hardware: We measured open-circuit voltage at 3.0V before dispatch. Under the low-drain RTC load, the BMS holds steady with no voltage sag — the SRAM retention current draw is typically in the microamp range.
• Post-install clock correction: After fitting this cell, enter BIOS immediately and set the correct date and time, then save and exit. The RTC circuit resets to a default date during the swap — leaving it uncorrected causes OS time errors and scheduled task failures until manually fixed.

BIOS clock resetting to January 2000 after every power cycle

The C720DC RTC circuit requires a minimum of 2.8V from the coin cell to hold register values. Once the original cell drops below that threshold, the board cannot retain the clock or BIOS settings between sessions. The symptom is always the same: date resets to a default value — commonly January 1st 2000 — on every cold boot. Replacing the cell and saving BIOS settings immediately after restores normal retention.

CMOS checksum error on boot after fitting a new coin cell

A checksum error immediately after a cell swap means the BIOS detected that stored values no longer match the checksum it calculated — because the depleted cell wiped everything before the swap. The new cell itself is not the cause. Enter BIOS setup, confirm or re-enter your settings, then select Save and Exit. The checksum error will not reappear once valid settings are written and the new 3V cell is maintaining the SRAM.