About this replacement
Lenovo ThinkPad Edge E220s / E420S — 14.8V Li-ion Replacement Battery (42T4932)
This 14.8V, 2900mAh Li-ion battery replaces the original cell in the Lenovo ThinkPad Edge E220s and E420S. It matches the OEM voltage rail and connector spec for both models. Capacity is 2900mAh / 42.92Wh as rated by the manufacturer.
- E220s and E420S compatibility: Both models share the same 14.8V four-cell architecture, connector pinout, and BMS handshake protocol — the same physical cell fits both without modification or adapter.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on ThinkPad Edge hardware. The BMS negotiated correctly with the EC, charge current stepped down at the expected threshold, and no fault codes were thrown during the test sequence.
- First-install calibration on ThinkPad Edge: After fitting this cell, 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 poor battery health immediately after replacement
ThinkPad Edge firmware reads EEPROM data written by the previous cell and compares it against the new cell's charge behaviour. Until the learn cycle completes, the BIOS flags the battery as degraded — even when the cell is brand new. This is not a fault with the replacement cell. Run one full discharge to the hibernate threshold and one uninterrupted charge to 100% to write fresh EEPROM reference data and clear the warning.
Laptop shuts down unexpectedly at 20–30% charge shown
The fuel gauge IC on the ThinkPad Edge estimates remaining capacity against a stored charge curve. When a new cell is installed, that stored curve belongs to the worn original battery. Under full CPU and display load, the new cell hits a voltage point the IC misreads as empty — triggering shutdown while the gauge still shows charge remaining. Two or three complete calibration cycles sync the IC's curve to the new cell's actual chemistry. After calibration, the cutoff will track accurately down to the cell's real low-voltage floor near 11.1V.