About this replacement
Toshiba Tecra Z40/Z50-A Series — 14.4V Li-ion Replacement Battery (PA5149U-1BRS)
This is a 14.4V, 3800mAh (54.72Wh) Li-ion replacement battery for the Toshiba Tecra Z40-A-17K and the broader Tecra Z40/Z50-A and Z40-B series. It matches the OEM part number PA5149U-1BRS and uses the same connector and BMS handshake as the original cell. Voltage, capacity, and physical dimensions align directly with what the Z40-A-17K chassis expects.
- Tecra Z40/Z50-A and Z40-B compatibility: These models share the same 14.4V power rail, identical four-pin connector, and the same BMS communication protocol. The BIOS on all variants reads the battery via the same EEPROM query, so one cell covers the full platform without modification.
- Bench tested on actual hardware: We ran this cell on a Tecra Z40-A under full CPU and display load. The BMS held voltage above the 10.8V cutoff threshold throughout discharge, and charge acceptance reached 100% without triggering the BIOS charge-limit flag.
- BIOS learn cycle after install: After fitting this battery, run a single full discharge to hibernate cutoff, then charge uninterrupted to 100%. This resets the BIOS battery learn cycle and clears the inaccurate health warning that appears after any cell swap on this platform.
Why the Tecra Z40-A BIOS reports poor health immediately after a battery swap
The Z40-A BIOS reads charge cycle count, rated capacity, and health state directly from the battery's EEPROM at boot. A new cell carries fresh EEPROM data that doesn't match the learned values the BIOS stored from the old battery. Until a full discharge-to-hibernate and uninterrupted recharge cycle is completed, the BIOS treats the mismatch as a fault condition. After one full calibration cycle, the health status updates to normal and the warning clears.
Tecra Z40-A shutting down at 20–30% charge remaining
This happens when the cell cannot hold its voltage above the system cutoff threshold under combined CPU and display load — the fuel gauge shows percentage remaining, but voltage collapses faster than the gauge predicts. It is almost always a fuel gauge IC calibration issue on cycles 1–3 with a new cell, not a faulty battery. The gauge IC needs to observe a full discharge curve to map the new cell's voltage-to-capacity profile accurately. Run the Z40-A fully down to automatic hibernate at least twice, charging to 100% each time, and the shutdowns will stop.