About this replacement
Panasonic Toughpad FZ-M1 / FZ-B2 — 7.2V Li-ion Replacement Battery (FZ-VZSU94K)
This is a 7.2V 5600mAh (40.32Wh) Li-ion replacement battery for the Panasonic Toughpad FZ-M1 and FZ-B2 rugged tablet series. It replaces OEM part numbers FZ-VZSU94K, FZ-VZSU95K, FZ-VZSU94W, and related variants. The cell chemistry and connector match the original so the battery seats and communicates with the tablet's BMS without modification.
- FZ-M1 and FZ-B2 platform fit: Both tablets share the same battery bay dimensions, 7.2V power rail, and SMBus handshake protocol. A single cell revision covers the full variant lineup — FZ-M1C and the JS-suffix models included — because Panasonic kept the BMS interface consistent across the production run.
- Bench tested on actual hardware: We ran this cell on a Toughpad FZ-M1 under a mixed CPU and display load cycle. The BMS accepted the cell, reported state-of-charge correctly after two conditioning cycles, and the protection circuit triggered at the expected low-voltage cutoff without false trips.
- First-cycle calibration on the FZ-M1: After fitting this cell, run the tablet on battery until it hibernates at the low-voltage cutoff, then charge uninterrupted to 100% before using it again. The FZ-M1's fuel gauge IC stores learned capacity data from the old cell — skipping this step leaves the OS reporting inaccurate percentage readings and can trigger a spurious "battery health poor" flag in Panasonic's battery status utility.
Why the FZ-M1 BIOS shows "battery health poor" after a cell swap
The Toughpad FZ-M1 stores battery health data in EEPROM on the BMS board, not on the cell itself. When a new cell goes in, the EEPROM still holds the degraded capacity figures from the old battery. Until the fuel gauge IC runs a full discharge-to-cutoff and recharge cycle against the new cell, the BIOS reads stale data and flags the battery as worn. One complete calibration cycle — full drain to hibernate cutoff, then uninterrupted charge to 100% — writes fresh capacity data to the EEPROM and clears the warning on the next boot.
FZ-M1 shutting down at 20–30% charge shown on screen
This happens when the cell voltage drops faster under load than the fuel gauge predicts — a mismatch between the OS percentage reading and actual cell state. On the FZ-M1, running GPS, a bright display, and active LTE simultaneously pulls enough current to expose the voltage cliff on a partially calibrated cell. The tablet's low-voltage protection circuit cuts power before the OS gauge reaches zero. After the first full calibration cycle the fuel gauge recalculates the discharge curve against real cell behaviour, and the premature shutdown stops. If it persists beyond two cycles, check that the cell resting voltage is above 7.0V before fitting.