About this replacement
IBM ThinkPad R60 / R61 — 10.8V Li-ion Replacement Battery (40Y6799)
This is a 10.8V, 6600mAh (71.28Wh) Li-ion battery for the IBM ThinkPad R60 and R61 series laptops. It cross-references over 30 OEM part numbers, including 92P1137, 92P1139, and 42T4504. Fits ThinkPad R60 9455, R60 9456, and all R61 variants that originally shipped with the 6-cell or 9-cell 10.8V pack.
- R60 and R61 battery platform: Both the R60 and R61 share the same 10.8V battery rail, connector pinout, and BMS communication protocol. IBM carried the same battery architecture across both generations, so one replacement covers the full lineup without firmware or connector changes.
- Bench tested on actual hardware: We seated this cell in a ThinkPad R60 and cycled it through charge and discharge under mixed CPU and display load. The BMS communicated correctly with the EC, charge current tapered as expected at end-of-charge, and no fault codes were thrown during the session.
- ThinkPad EC learn cycle after install: After fitting this battery, run it down until the laptop hibernates on low voltage, then charge it uninterrupted to 100%. This one full discharge-to-hibernate cycle resets the embedded controller's battery learn table and clears the inaccurate health warning that appears in Lenovo/IBM Power Manager after every cell swap.
Why the ThinkPad R60 reports poor battery health immediately after a new cell is installed
The ThinkPad EC reads health data stored in the battery's EEPROM — capacity, cycle count, and design Wh. A new replacement cell carries factory EEPROM values that do not match the EC's learned profile for the old pack, so the EC flags the mismatch as degraded health. This is not a fault with the replacement battery. Run one full discharge-to-hibernate cycle followed by a full uninterrupted charge. After that calibration pass, the EC rewrites its learn table against the new cell's actual data and the health warning clears.
ThinkPad R60 shutting down abruptly at 15–25% charge shown
This happens when the cell's actual voltage under load drops faster than the fuel gauge IC predicts. The IC was calibrated against the old pack's discharge curve, not the new cell's. Under full CPU plus display load, the voltage cliff arrives earlier than the percentage readout suggests, and the EC triggers a hard shutdown before the OS can hibernate. Run two to three full discharge-to-hibernate-then-100% charge cycles. After each pass the fuel gauge IC recalibrates its curve against the new cell, and the remaining percentage readout becomes accurate — target a stable reading down to at least 10% before treating the gauge as trustworthy.