About this replacement
Lenovo ThinkBook 14p G2 ACH — 15.44V Li-Polymer Replacement Battery (L20B4PD2)
This is a 15.44V, 3850mAh (59.44Wh) Li-Polymer battery for the Lenovo ThinkBook 14p G2 ACH series, including the 20YN000LUS and related variants. It replaces OEM part numbers L20B4PD2, L20C4PD2, L20D4PD2, SB11C04258, and SB11C04259. The cell fits the slim 14-inch ThinkBook chassis and connects directly to the existing battery management circuit.
- ThinkBook 14p G2 ACH compatibility: All covered models share the same 15.44V four-cell architecture, connector pinout, and BMS handshake protocol. The EEPROM on this cell carries the correct capacity and chemistry identifiers that the ThinkBook firmware expects during initialisation.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a ThinkBook 14p G2 platform. The BMS accepted the cell without a firmware rejection event, voltage held steady across light and moderate CPU loads, and the charge controller reached full capacity without interruption.
- Post-installation discharge cycle: 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 commonly appears after any cell swap on ThinkBook hardware.
BIOS reporting battery health as poor after replacement
The ThinkBook BIOS reads health status from EEPROM data accumulated by the old cell over hundreds of cycles. When a new cell is installed, that stored wear data does not automatically clear. The firmware compares the new cell's initial readings against the old EEPROM baseline and flags a mismatch as degraded health. Running a full discharge-to-hibernate followed by an uninterrupted charge to 100% triggers the BIOS battery learn cycle, which rewrites the health record against the new cell's actual parameters.
Laptop shutting down at 20–30% remaining after battery swap
This happens when the fuel gauge IC has not yet calibrated against the new cell's voltage curve. The IC still maps percentage readings against the old cell's discharge profile, so the voltage cliff — where the cell drops sharply under CPU and display load — arrives earlier than the gauge predicts. The system hits the hardware low-voltage cutoff while the OS still shows 20–30% remaining. Two to three full charge-discharge cycles recalibrate the fuel gauge IC; after that, shutdowns should align with the gauge reading below 5V per cell.