About this replacement
IBM ThinkPad 240 Series — 11.1V Li-ion Replacement Battery (FRU 02K6606)
This 11.1V, 3400mAh (37.74Wh) lithium-ion battery replaces the original cell in the IBM ThinkPad 240, 240x, and 240z. It covers OEM part numbers FRU 02K6606, 02K6687, 02K6924, FRU 02K6691, 02K6580, 02K6607, 02K6763, FRU 02K6608, FRU 02K6690, 02K6923, and 02K6762. Physical dimensions are 108.50 × 65.70 × 12.80mm — verify against the original before installing.
- ThinkPad 240 platform compatibility: The 240, 240x, and 240z share the same battery bay geometry, connector pinout, and BMS handshake protocol. One cell fits all three variants without modification.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a ThinkPad 240z. The BMS negotiated correctly with the system board, and the protection circuit tripped at the expected low-voltage cutoff without requiring a manual reset.
- ThinkPad 240z post-swap learn cycle: After installing, run one 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 every cell swap on this platform.
BIOS reporting battery health as poor immediately after replacement
The ThinkPad 240 BIOS reads EEPROM data written by the original factory cell. When a new cell arrives, that EEPROM data doesn't match the new cell's charge history, so the BIOS flags health as poor or unknown. This is not a fault with the replacement cell. Run two full discharge-to-hibernate and charge-to-100% cycles. After the second cycle, the BIOS recalibrates against the new cell and the warning clears.
Laptop shutting down at 20–30% charge shown on the gauge
This happens when the fuel gauge IC hasn't calibrated against the new cell's actual voltage curve yet. The gauge shows 25% while the cell voltage has already dropped below the BMS cutoff threshold under CPU and display load — the system shuts down to protect the cell. It's not a faulty battery. Complete two uninterrupted full discharge-to-hibernate cycles followed by full charges, and the fuel gauge IC recalculates its reference points. After calibration, shutdown should not occur above 5–7% remaining.