Fujitsu Lifebook AH77/M Compatible Battery 10.8V 4050mAh

Fujitsu Lifebook AH77/M Series — 10.8V Li-Polymer Replacement Battery (CP641484-01)

This 10.8V, 4050mAh (43.74Wh) lithium-polymer battery replaces the CP641484-01 in the Fujitsu Lifebook AH77/M, AH77/S, A556, and A556/G. It uses the same connector and BMS handshake as the original cell, so the laptop recognises it on first boot. Voltage and capacity match the factory specification exactly.

• AH77 and A556 series compatibility: The AH77/M, AH77/S, A556, and A556/G share the same 10.8V power rail, physical connector, and BMS communication protocol. One cell works across all four models without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the AH77 platform and confirmed the BMS communicated state-of-charge correctly throughout. The protection circuit tripped cleanly at the low-voltage cutoff threshold with no unexpected shutdowns during testing.
• First-cycle conditioning on the AH77: After installing, let the battery drain fully until the laptop hibernates, then charge uninterrupted to 100%. This resets the BIOS battery learn cycle and clears the inaccurate health warning that appears on first boot after any cell swap.

BIOS reporting poor battery health immediately after fitting the CP641484-01

The Lifebook BIOS reads health data stored in the old cell's EEPROM and compares it against the new cell's reported state. A fresh cell has no discharge history, so the BIOS flags it as unknown or degraded. This is a firmware interpretation issue, not a fault with the battery. Running one full discharge-to-hibernate followed by a full uninterrupted charge gives the fuel gauge IC enough data to recalibrate and clears the warning within two to three cycles.

Lifebook AH77 shutting down at 20–30% shown on the fuel gauge

This happens when the fuel gauge IC's calibration is still based on the old cell's voltage curve. The new cell hits a voltage cliff under combined CPU and display load at a point the gauge still reads as 20–30%. The laptop interprets the sudden voltage drop as a critical battery event and forces shutdown. Run two full discharge-to-hibernate cycles with no hibernation threshold override, then charge to 100% each time — by the third cycle the gauge aligns to the new cell's actual curve and the early shutdowns stop.