IBM ThinkPad i1400 02K6524 Replacement Battery 9.6V 4000mAh

IBM ThinkPad i1400 Type 2611 Series — 9.6V Li-ion Replacement Battery (02K6524)

This 9.6V, 4000mAh (38.4Wh) Li-ion battery replaces the original cell in IBM ThinkPad i1400 laptops across the Type 2611 range. It fits multiple 2611 sub-models, including the 435, 434, 41x, and 45x variants where specified. Voltage, connector, and BMS handshake match the original IBM specification.

• ThinkPad i1400 Type 2611 sub-model coverage: These sub-models share the same 9.6V power rail, physical form factor, and battery connector pinout. OEM part numbers 02K6524, 02K6525, 02K6563, BTP-1731, BTP-1831, FRU 02K6526, 60.45B04.011, and 91.45B28.001 all cross-reference to this cell.
• Bench tested on actual hardware: We cycled this battery through charge and full discharge on the ThinkPad i1400 platform. The BMS engaged at the correct voltage floor and communicated cell status to the BIOS without error flags on a clean cycle.
• Post-install calibration tip: After fitting this cell, run the laptop from full charge down to automatic hibernate cutoff without interruption, then charge uninterrupted back 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 immediately after replacement

The ThinkPad i1400 BIOS reads health data from EEPROM stored on the battery controller, not from live cell measurements. When a new cell is installed, that EEPROM data does not match the BIOS's learned values from the previous cell, so it flags the battery as degraded. This is not a fault with the replacement — it is a calibration mismatch. Run one full discharge-to-hibernate then a complete uninterrupted charge, and the BIOS will relearn the cell and clear the warning.

ThinkPad i1400 shutting down abruptly at 20–30% charge shown

This happens when the fuel gauge IC has not yet calibrated against the new cell's actual voltage curve. The IC underestimates how quickly voltage drops under combined CPU and display load, and the laptop hits the hardware cutoff before the displayed percentage reaches zero. It is not a faulty battery — the gauge needs two or three full discharge and charge cycles to map the new cell accurately. After calibration cycles, the shutdown point should align within a few percent of actual charge remaining, typically resolving above 4.8V total pack voltage at cutoff.