About this replacement
VeriFone NURIT 8020 / 802B-WW-M05 — 3V Lithium CMOS Backup Battery
This is a 3V 550mAh lithium coin cell replacement for the VeriFone NURIT 8020 and 802B-WW-M05 payment terminals. It backs the RTC circuit and SRAM that hold transaction records, terminal configuration, and the real-time clock when main power is removed. Without a functioning CMOS cell, the terminal loses those settings every time mains power drops.
- NURIT 8020 and 802B-WW-M05 compatibility: Both models share the same CMOS backup circuit and coin cell socket. The cell supplies continuous low-current voltage to the RTC and SRAM — the terminal does not draw from main power for this function at all.
- Bench tested on actual hardware: We measured open-circuit voltage on arrival and confirmed stable retention voltage above 2.8V under the low-drain SRAM load. The cell held terminal configuration and clock data through repeated mains-off cycles without reset.
- Post-swap clock correction on the NURIT 8020: After fitting the new cell, manually enter the correct date and time through the terminal's supervisor menu and save. The CMOS circuit powers the RTC independently, and any interruption during the swap resets the clock to a factory default — the new cell does not restore the previous time automatically.
BIOS clock resetting to a default date after every power cycle on the NURIT 8020
The RTC circuit on the NURIT 8020 requires a continuous minimum retention voltage of 2.8V from the CMOS cell to keep the clock running. When the cell drops below that threshold, the RTC loses power the moment mains is disconnected and resets to a default factory date on next boot. A degraded cell may still show 2.9V at rest but collapse under even the tiny SRAM load — open-circuit voltage alone does not confirm a healthy cell. Replacing the cell and setting the correct date through the supervisor menu resolves the cycle.
Terminal configuration wiped every time mains power is removed
The NURIT 8020 stores terminal configuration in SRAM, which requires uninterrupted low-level voltage from the CMOS cell to retain data when main power is absent. A depleted cell can no longer sustain that voltage, so the SRAM loses its contents the moment the terminal is unplugged. This is a different symptom from a clock reset — the terminal may boot with the correct time but show a blank or default configuration. Fit the replacement cell, confirm open-circuit voltage reads 3.0V, then re-enter terminal settings and save before disconnecting power.