Fujitsu FPCBP155 LifeBook T4210 Replacement Battery 10.8V 4600mAh

Fujitsu LifeBook T4210 Series — 10.8V Li-ion Replacement Battery (FPCBP155)

This is a 10.8V 4600mAh Li-ion battery for the Fujitsu LifeBook T4210, T4215, and T4220 Tablet PC. These are convertible tablet-notebook hybrids from the mid-2000s that depend on a working battery for any unplugged operation. This cell replaces OEM part numbers FPCBP155, FPCBP155AP, and S26391-F405-L600.

• T4210, T4215, and T4220 compatibility: All three models share the same 10.8V battery rail, connector pinout, and BMS communication protocol — one cell fits all three without modification.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the T4210 platform. The BMS handshook correctly, charge termination triggered at 100%, and the protection circuit responded to over-current conditions as expected.
• Post-install calibration on the T4210: After fitting this cell, run the laptop down to hibernate-cutoff under normal use, then charge it uninterrupted to 100%. This resets the BIOS battery learn cycle and clears the inaccurate health warning that appears after every cell swap on this platform.

BIOS reporting poor battery health after swapping the cell on the T4210

The T4210 BIOS reads health data stored in the battery's EEPROM, not from live cell measurements. When a new cell arrives, that EEPROM data does not match the old unit's learned values, so the system flags the battery as degraded. This is a data mismatch, not a fault with the cell itself. Running one full discharge-to-hibernate then a complete uninterrupted charge lets the BIOS rewrite its learned capacity values and clear the warning.

Fuel gauge jumping erratically for the first few cycles after replacement

The fuel gauge IC on the T4210 estimates remaining capacity based on charge and discharge curves it learned from the previous cell. A new cell has different internal resistance and a slightly different voltage curve, so the gauge reads wildly off until it recalibrates. Expect inaccurate percentage readings for the first two to three full cycles — this is normal IC behaviour, not a battery defect. After two or three full discharge and charge cycles, the gauge IC locks onto the new cell's curve and the readout stabilises.