Compaq Presario CQ60 CMOS Replacement Battery 3V 200mAh

Compaq Presario CQ60 / CQ50 / CQ70 — 3V Lithium CMOS Backup Battery

This is a 3V 200mAh lithium coin cell replacement for the CMOS/RTC circuit on the Compaq Presario CQ60, CQ50, CQ70, and CQ60-320SA motherboards. It sits in a retention socket on the board and holds system settings — date, time, and BIOS configuration — when mains power is removed. When the cell drops below the minimum retention voltage, the RTC circuit loses its reference and resets to a factory default on every boot.

• CQ50 / CQ60 / CQ70 platform fit: These three Presario lines share a common board layout from the same HP mobile platform generation. The CMOS socket, contact orientation, and cell footprint are identical across them — 20mm diameter, 3.8mm height.
• Bench tested on actual hardware: We measured open-circuit voltage at 3.0V and confirmed the cell seated correctly in a CQ60 socket. The BIOS clock held its value through a full mains disconnect with no bleed resistor active.
• Post-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 January 1, 2000 — on first power-up after a cell swap, and that must be corrected manually before the OS loads.

BIOS clock resetting to 2000 after every power cycle on the CQ60

The RTC circuit on the Presario CQ60 requires the CMOS cell to hold a minimum of 2.8V to retain clock data. Once the cell dips below that threshold, the SRAM loses its value the moment mains power drops. The symptom is the system clock reverting to a default date — typically January 1, 2000 — on every cold boot. A new 3V cell restores retention voltage and stops the reset cycle.

CMOS checksum error on boot after replacing the coin cell

A checksum error immediately after fitting a new cell usually points to a contact spring issue rather than a bad cell. If the retention socket spring is flattened or oxidised from the old cell, it won't make consistent electrical contact — the CMOS circuit sees an intermittent supply and throws a checksum fault. Check the socket spring with a flat tool to restore tension, clean contact surfaces with isopropyl alcohol, then reseat the cell firmly. If voltage at the socket reads below 2.9V with the cell installed, the spring contact is the fault.