About this replacement
IBM ThinkPad 240 Series — 11.1V Li-ion Replacement Battery (FRU 02K6608)
This 11.1V, 1700mAh (18.87Wh) Li-ion battery replaces the original cell in the IBM ThinkPad 240, 240x, and 240z. It fits all three models in this ultraportable series and matches the original voltage rail and connector. OEM part numbers covered: FRU 02K6608, FRU 02K6606, and FRU 02K6690.
- ThinkPad 240 series fit: The 240, 240x, and 240z share the same battery bay dimensions, 11.1V rail, and connector pinout. One cell covers all three variants without modification.
- Bench tested on actual hardware: We cycled this cell through charge, discharge, and load on the ThinkPad 240 platform. The BMS communicated correctly with the system board and held voltage stable under CPU and display load.
- First-cycle reset on the 240 series: After fitting this cell, run the ThinkPad down to hibernate cutoff on battery alone — no AC. Then charge uninterrupted to 100%. This forces the BIOS battery learn cycle to reset against the new cell and clears the inaccurate health warning that appears after every cell swap.
BIOS reporting poor battery health immediately after fitting a new cell
The ThinkPad 240 BIOS reads health data stored in the outgoing cell's EEPROM, not from live voltage measurements. When a new cell goes in, that EEPROM data is gone and the BIOS flags the battery as degraded or unknown. This is not a fault with the replacement cell. One full discharge-to-hibernate followed by a complete uninterrupted charge rewrites the learn cycle and the health status updates correctly.
Laptop shuts down with 20–30% charge still showing on the gauge
This happens when the fuel gauge IC has not yet calibrated against the new cell's actual discharge curve. The gauge inherited the old cell's profile and calls the cutoff point too early. The ThinkPad 240 draws sharply under combined CPU and backlight load, exposing this mismatch faster than idle use would. Run two to three full discharge-to-hibernate and full-charge cycles — the gauge recalibrates and the premature shutdowns stop.