About this replacement
Lenovo ThinkPad X220 Tablet Series — 11.1V Li-ion Replacement Battery (0A36285)
This 11.1V 4400mAh (48.84Wh) Li-ion battery is a direct cell swap for the ThinkPad X220 Tablet, X220i Tablet, X220t, and X230t. It fits the convertible form factor that pivots between laptop and tablet modes. Voltage and connector match the original Lenovo spec for these models.
- X220 Tablet and X230t compatibility: These models share the same 11.1V battery rail, connector pinout, and BMS communication protocol. OEM part numbers 0A36285, 0A36286, 42T4879, 42T4881, and 45N1078 all cross to this cell without modification.
- Bench tested on actual hardware: We cycled this battery on a ThinkPad X220 Tablet and confirmed the BMS handshake completes correctly — charge current initialises at full rate, and the protection circuit trips at the expected low-voltage cutoff without false shutdowns.
- BIOS learn cycle after installation: After fitting this cell, run one full discharge down 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 ThinkPad hardware.
BIOS reporting battery health as poor immediately after replacement
ThinkPad firmware stores cell health data in EEPROM from the previous battery. When a new cell is installed, the BIOS reads stale EEPROM values and flags the battery as degraded — even at 100% charge. This is not a fault with the new cell. Run the Lenovo Battery Gauge Reset tool or complete two full discharge-to-hibernate and full-recharge cycles. After calibration, the BIOS should report capacity above 90% of rated 48.84Wh.
Laptop shuts down at 20–30% charge shown on the fuel gauge
This happens when the fuel gauge IC has not calibrated against the new cell chemistry. The gauge IC carries over learned capacity curves from the old battery and misjudges the voltage cliff. Under combined CPU and display load, the cell voltage drops faster than the stale curve predicts, triggering an emergency shutdown before the displayed percentage reaches zero. Complete a full uninterrupted discharge to hibernate — do not plug in mid-cycle — then charge to 100%. The fuel gauge recalibrates against the actual cell and the shutdowns stop.