Gateway Solo 2100 CMOS Backup Battery 7.2V 20mAh Ni-MH

Gateway Solo 2100 Series — 7.2V Ni-MH CMOS Backup Battery

This is a 7.2V, 20mAh Ni-MH CMOS backup battery for the Gateway Solo 2100, Solo 2200, Solo 2300, and Solo 2300LS laptops. It powers the RTC circuit and SRAM on the motherboard, keeping system date, time, and BIOS settings intact when the machine is unplugged or powered off. Capacity figure is 20mAh (0.14Wh) as per the product specification.

• Solo 2100–2300 series fit: These models share the same motherboard CMOS socket, connector pitch, and RTC circuit voltage rail. The 7.2V Ni-MH cell format is consistent across the range, so one part number covers all listed variants without modification.
• Bench tested on actual hardware: We ran this cell against the Solo motherboard's retention circuit. The BMS handshake confirmed stable voltage supply above the 2.8V minimum retention threshold, with no checksum errors triggered during power cycle testing.
• Post-installation RTC reset: After fitting the new cell, enter BIOS immediately and set the correct date and time, then save and exit. The CMOS cell powers the RTC circuit directly — any gap in supply resets the clock to its default value, and that must be corrected manually after every swap.

BIOS clock resetting to a default date after every power cycle

When the CMOS cell drops below the 2.8V minimum retention voltage, the RTC circuit loses its reference and resets to a factory default date on every boot. The cell doesn't need to be fully dead — even a partially degraded cell that reads above zero under no load can collapse under the microamp draw of the RTC. The Solo 2100's RTC circuit has no secondary hold capacitor, so there's no grace period once the cell voltage sags. Replacing the cell and setting the correct date in BIOS solves this permanently.

CMOS checksum error on boot with the old cell still fitted

A checksum error at POST means the BIOS has detected that stored configuration values no longer match their expected checksum — almost always caused by a completely depleted CMOS cell that allowed SRAM contents to corrupt. The Solo's BIOS writes a checksum across all stored settings; if the cell drops out mid-session, partial writes leave mismatched data. Swapping the cell clears the hardware cause, but the BIOS will still need reconfiguration after the first boot. Enter setup, restore your settings, save, and exit — the checksum recalculates automatically on the next POST.