Acer TravelMate 240 CMOS Compatible Battery 3V 200mAh

Acer TravelMate 240 / 250 — 3V Lithium CMOS Backup Battery (417076-001)

This is a 3V lithium coin cell CMOS backup battery rated at 200mAh. It fits the Acer TravelMate 240, TravelMate 250, Aspire 4920, Aspire 4920G, and several other Acer notebook models. It replaces OEM part numbers 417076-001 and 23.22047.001.

• TravelMate 240 / 250 and Aspire 4920 series compatibility: These models share the same motherboard CMOS circuit, coin cell footprint, and connector pinout. The same 3V lithium cell backs the RTC and SRAM on all of them. One cell covers the full compatibility list.
• Bench tested on actual hardware: We measured open-circuit voltage before dispatch. Every cell shipped sits above 2.95V at rest. The RTC circuit on the TravelMate 240 motherboard held stable BIOS settings through repeated power cycles with no AC input connected.
• After installation — BIOS date and time correction: After fitting this cell, boot into BIOS setup and manually set the correct date and time, then save and exit. The CMOS circuit powers the RTC directly. Any power interruption during the swap resets the clock to a factory default value — it will not self-correct without a manual save.

BIOS clock resetting to 2000 after every power cycle on the TravelMate 240

The RTC circuit on this motherboard requires a minimum coin cell retention voltage of 2.8V to hold register values. Once the original cell drops below that threshold, the clock and CMOS settings reset to a hardcoded default — typically 1 January 2000 — on every cold boot. This happens even if AC power is connected during normal use, because the CMOS cell is the sole backup when mains power is absent or the laptop is off. Fitting a fresh 3V cell and saving the correct date in BIOS resolves it immediately.

CMOS checksum error on boot after fitting a new coin cell

A checksum error immediately after a cell swap usually means the motherboard lost all stored CMOS data while the old cell was removed — the SRAM has no retention voltage during the gap between removal and installation. The BIOS detects that its stored checksum no longer matches the (now blank) CMOS data and throws the error. This is expected behaviour, not a fault with the new cell. Enter BIOS setup, re-enter your settings, save and exit — the checksum recalculates and the error clears on the next boot.