About this replacement
Dell Latitude E4200 / E4300 — 3V Lithium Replacement CMOS Battery (GC02000KG00)
This is a 3V, 200mAh lithium coin cell that replaces the CMOS backup battery on the Dell Latitude E4200 and E4300. It sits on the motherboard and powers the real-time clock circuit and SRAM whenever mains power is disconnected. Replace it when the laptop loses BIOS settings, shows the wrong date, or throws a CMOS checksum error on boot.
- E4200 and E4300 compatibility: Both models share the same motherboard CMOS socket and use the GC02000KG00 cell. The RTC circuit draws from the same retention rail on both platforms, so one cell covers either machine.
- Bench tested on actual hardware: We seated this cell in the E4200 socket and measured retention voltage at 3.0V under the RTC load. The BMS handshake on the main board accepted the cell without error flags, and SRAM held its state through a full mains disconnect cycle.
- Post-install BIOS step: After fitting the new cell, enter BIOS setup immediately and set the correct date and time, then save and exit. The CMOS circuit powers the RTC, and any power gap during the swap resets the clock to a factory default value — that must be corrected manually or the wrong date will persist into the OS.
BIOS clock resetting to 2000 after every power cycle on the E4200
The E4200 RTC circuit requires a minimum retention voltage of 2.8V from the CMOS cell to hold the clock and SRAM contents. Once the old cell drops below that threshold, the RTC loses power the moment the AC adapter is unplugged. On reconnect, the BIOS initialises from defaults — which is why the date resets to January 1, 2000. A depleted cell can still read above 2.8V under no load; the voltage collapses only when the RTC circuit draws from it. Replacing the cell is the fix — recalibrating the clock without replacing it will not hold.
CMOS checksum error on boot after fitting a new coin cell
A checksum error immediately after a new cell install usually points to a contact spring issue, not the cell itself. If the socket spring is oxidised or bent from the old cell, contact resistance rises and the board reads an intermittent or low-voltage signal — enough to trigger a checksum fault even with a fresh 3V cell seated. Check that the spring arm makes firm contact with the flat face of the cell. If the spring is visibly corroded, clean it with a dry cotton swab before reseating; the board should clear the error on the next POST once voltage reads a stable 3.0V.