Xerox 490 Printer PLC Replacement Battery 3.6V 1200mAh

Xerox 490 / 980 Printer — 3.6V Li-SOCl2 Replacement Battery

This is a 3.6V lithium thionyl chloride cell rated at 1200mAh (4.32Wh), built to the same footprint as the original backup cell in Xerox 490 and 980 printers. It powers the onboard SRAM and real-time clock, keeping programmed settings and the system clock intact when mains power is removed. Without a live backup cell, both are lost the moment the printer powers down.

• 490 and 980 compatibility: Both models use the same 3.6V backup architecture and identical cell footprint (26.36 × 15.50 × 14.60mm). The SRAM retention circuit draws continuously from this cell regardless of mains state, so both printers consume the backup cell at the same rate over time.
• Bench tested on actual hardware: We confirmed stable float voltage and verified the cell holds the SRAM rail above the 2.5V retention threshold under continuous low-current draw. The BMS on this chemistry is passive — no handshake, no reset — so what matters is cell voltage, not protocol.
• Hot-swap is mandatory on this cell: Always replace this battery with the printer powered on and running. Li-SOCl2 cells in backup roles have no charge path — the printer cannot recover SRAM from a dead cell. Pull the old cell and seat the new one before power is interrupted.

Xerox 490 losing saved settings every time it powers off

The 490 stores user-configured parameters and network settings in SRAM, which requires a constant low-level voltage from the backup cell to retain data. Once the Li-SOCl2 cell drops below approximately 2.5V, the SRAM loses its retention voltage and flushes on every power cycle. This is not a firmware fault — the settings are genuinely gone, not hidden. Replace the cell while the printer is live and reconfigure once; the new cell will hold those settings indefinitely at its rated self-discharge rate.

New cell reading below 3.6V immediately after installation

Li-SOCl2 cells develop a passivation layer on the lithium anode during storage, which temporarily suppresses open-circuit voltage. A freshly installed cell may read as low as 3.2V on the printer's diagnostic readout in the first few hours. This is normal and not a sign of a faulty or partially discharged cell. The passivation layer breaks down under load — leave the printer powered on and the cell will stabilise at or above 3.5V within 12–24 hours.