HP EliteBook 820 G3 CMOS Replacement Battery 3V 150mAh

HP EliteBook 820 G3 / Folio 9470m — 3V Lithium Replacement CMOS Battery (702853-001)

This is the 3V, 150mAh lithium coin cell that backs the RTC circuit and SRAM on HP EliteBook 820 G3, Folio 9470m, 9480m, and EliteBook Revolve 810 G3 motherboards. It keeps the system clock, BIOS settings, and hardware configuration intact when mains power is removed. When this cell drops below retention voltage, the board loses everything it was holding.

• EliteBook 820 G3 / Folio 9470m platform fit: These models share the same motherboard footprint for the CMOS cell — same contact spring orientation, same 28.70 × 23.20 × 3.00mm envelope, and the same 702853-001 OEM part number across the listed variants. No modification needed to seat the cell.
• Bench tested on actual hardware: We confirmed open-circuit voltage at 3.0V before dispatch. The cell was seated in the socket and BIOS retention was verified across a full mains disconnect cycle — date, time, and boot order held without reset.
• Post-installation 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 value during the swap — even a brief power interruption clears it. Set it once correctly and the cell holds it from there.

BIOS clock resetting to 2000 after every power cycle

When the CMOS cell drops below approximately 2.8V, it can no longer hold the RTC circuit between power cycles. The board reverts to a hardcoded default date — typically 1 January 2000 — on every cold boot. This happens even when the laptop runs normally on mains power, because the cell only takes over when AC is disconnected. A cell reading below 2.8V under light load needs replacing; no amount of BIOS resets will fix a voltage problem.

CMOS checksum error on boot after fitting a new coin cell

A checksum error immediately after installing a new cell usually means the BIOS lost all stored settings when the old cell was removed. The board recalculates the checksum against blank SRAM and flags the mismatch. Enter BIOS setup, load defaults, then manually re-enter your settings — boot order, time, date, and any custom hardware flags. Save and exit cleanly. If the error persists across reboots with a confirmed 3.0V cell installed, inspect the contact spring on the motherboard for oxidation or mechanical damage preventing full contact.