VeriFone VX680 Replacement CMOS Battery 3V 550mAh

VeriFone VX680 — 3V Lithium CMOS Backup Battery

This is a 3V 550mAh lithium coin cell that replaces the CMOS backup battery inside the VeriFone VX680 payment terminal. It fits the VX680 and VX680 wireless terminal variants. Its sole job is to keep the real-time clock (RTC) running and retain configuration data when the terminal loses main power.

• VX680 and VX680 wireless terminal: Both models share this CMOS cell because they use the same RTC circuit and SRAM backup rail. The cell holds the clock and settings at a retention voltage floor of 2.8V — drop below that and the terminal loses both.
• Bench tested on actual hardware: We ran this cell through RTC retention and SRAM continuity checks. Voltage held steady above 3.0V and the BMS-adjacent protection circuit responded correctly to load — no false drops.
• Post-install clock correction: After swapping the cell, enter the VX680 setup menu and manually set the correct date and time before the terminal reconnects to any network. The RTC resets to a default value the moment the old cell is pulled — it does not recover the previous time automatically.

CMOS checksum error on the VX680 at boot — what triggers it

A checksum error appears when the terminal reads its stored configuration and finds it corrupted. This happens when the CMOS cell drops below retention voltage and SRAM loses power mid-session. The terminal cannot verify the stored data against its checksum, so it flags the error and resets to defaults. Replacing the cell resolves the root cause, but you still need to re-enter any custom configuration the terminal held.

New coin cell installed but VX680 clock still resets to wrong date

A fresh lithium coin cell ships at storage voltage, which can read slightly below 3.0V on a meter. Once installed and under light RTC load, it rises to its rated voltage within a short period — this is normal cell behaviour, not a defect. If the clock still resets after the cell has settled, check the contact spring in the battery holder for oxidation or deformation from the old cell. A bent or corroded spring breaks the circuit intermittently, reading as a missing cell. Clean the contact with a dry cloth or gently reseat it, then set the date and time again to confirm retention.