Compaq Presario V6100 CMOS Replacement Battery 3V 200mAh

Compaq Presario V6100 / V6000 Series — 3V Lithium CMOS Replacement Battery

This is a 3V lithium coin cell replacement for the CMOS/RTC circuit on Compaq Presario V6000, V6100, V6400, and G6000-G6032EA laptops. Capacity is 200mAh (0.6Wh). It powers the real-time clock and SRAM that stores BIOS settings when the laptop is off or unplugged from mains power.

• V6000/V6100/V6400 and G6000 series fit: These models share the same motherboard CMOS socket geometry and RTC circuit voltage rail. The 3V retention voltage and physical footprint — 26.25 x 20.12 x 4.60mm — match the original cell across all listed variants.
• Bench tested on actual hardware: We seated this cell in a V6100 board and measured 3.0V at the CMOS socket contacts. The RTC held time and BIOS settings across repeated cold-power cycles with mains disconnected.
• First boot after swap: After installing, enter BIOS immediately and set the correct date and time, then save and exit. The CMOS cell powers the RTC circuit, and any power interruption resets the clock to a factory default value that must be manually corrected after the swap.

BIOS clock resetting to 2000 after every power cycle

The Presario V6100 RTC circuit requires the CMOS cell to hold at least 2.8V to retain the clock and SRAM contents. Once the original cell drops below that threshold, the RTC loses power the moment mains is removed. The system then boots with the last hardcoded default date — typically 1 January 2000 — because the clock register has reset. Replacing the coin cell restores retention voltage and stops the reset loop.

CMOS checksum error on boot after fitting a new cell

A checksum error after a cell swap usually means the BIOS compared stored settings to what it found in CMOS SRAM and got a mismatch — a sign the original cell had fully depleted and all stored values were lost. The new cell is not the fault; the stored configuration is simply gone and needs to be re-entered. Boot into BIOS setup, restore your settings manually, set the correct date and time, then save and exit. The checksum error will not return once valid settings are written.