Panasonic Toughpad FZ-A1 CMOS Battery 3V 40mAh 0702.12

Panasonic Toughpad FZ-A1 — 3V Lithium Replacement Battery (0702.12)

This is a 3V 40mAh lithium CMOS backup battery for the Panasonic Toughpad FZ-A1, FZ-A1 4G, and FZ-A1BDAAA1M. It replaces OEM part 0702.12 and powers the real-time clock and SRAM when main power is disconnected. When this cell depletes, the tablet loses system settings and clock data on every power cycle.

• FZ-A1 series compatibility: The FZ-A1, FZ-A1 4G, and FZ-A1BDAAA1M share the same motherboard layout and CMOS circuit, drawing from the same 0702.12 cell footprint. All three variants use an identical connector and retention voltage threshold, so one part number covers the full series.
• Bench tested on actual hardware: We verified cell voltage at rest and under RTC load. The CMOS circuit draws microamps continuously, and the BMS on this replacement holds retention voltage above the 2.8V minimum required to keep SRAM and clock data intact.
• Post-installation clock correction: After swapping the cell, enter the Toughpad's system settings and manually set the correct date and time, then save and exit. The RTC circuit loses its reference the moment the old cell is removed, and the clock defaults to a reset value until corrected. This step is mandatory — skipping it causes timestamp errors in field service logs and data capture apps.

BIOS clock resetting to a default date after every power cycle on the FZ-A1

The FZ-A1's RTC circuit depends entirely on this coin cell when mains or main battery power is absent. Once the cell drops below 2.8V, it can no longer sustain the SRAM holding the clock value, so the system reverts to a factory default timestamp on every cold boot. A depleted cell often still shows a surface voltage close to 3V on a multimeter under no load — that reading is misleading. Under the microamp draw of the RTC circuit, a worn cell collapses quickly. Replacing the 0702.12 cell and setting the correct date in system settings resolves this immediately.

CMOS checksum error on boot after fitting a new coin cell

A checksum error after a cell swap usually means the CMOS stored a corrupted configuration before the old cell fully failed, and the new cell is now powering that bad data. It can also result from a contact spring that is bent flat or oxidised, preventing the new cell from seating with consistent pressure. Check that the spring makes firm contact with the cell's negative face and that there is no corrosion residue from the old cell. Enter system settings, clear or reset to defaults, re-enter the correct date and time, save, and reboot — the checksum error clears once valid data is written back to CMOS.