About this replacement
Lenovo Legion 5-15ACH6A — 15.36V Li-Polymer Replacement Battery (L20C4PC0)
This 15.36V, 3850mAh (59.14Wh) Li-Polymer battery replaces the original cell in the Lenovo Legion 5-15ACH6A and related Legion 5 15-inch notebooks. It matches the OEM part numbers L20C4PC0, L20M4PC0, L20D4PC0, 5B11B48827, 5B11B48819, and SB11B48820. Direct swap — same connector, same dimensions (229.10 x 80.34 x 8.26mm), same 4-cell configuration.
- Legion 5 15-inch platform compatibility: The Legion 5-15ACH6A, 15ACH6, 15ACH6H, and 15ITH6 all share the same battery bay geometry, 15.36V rail, and BMS handshake protocol — one cell covers the full platform without electrical modification.
- Bench tested on actual hardware: We ran this cell on a Legion 5-15ACH6A unit under combined CPU and display load. The BMS held the charge curve through all four cells without mid-cycle cutoff, and the protection circuit tripped correctly at the low-voltage threshold.
- Post-swap calibration step: After fitting this cell, run a 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 in Lenovo Vantage after every cell swap.
BIOS reporting battery health as poor after replacement
The Legion BIOS reads health data stored in the battery's EEPROM and compares it against the previous cell's wear history. A brand-new cell has a fresh EEPROM with no accumulated cycle data, which the BIOS can misread as an unknown or degraded unit. This is not a fault with the replacement cell. Run the Lenovo Vantage battery learn cycle — or manually discharge to hibernate-cutoff and recharge to 100% — and the health status will update correctly within one to three cycles.
Laptop shutting down at 20–30% charge shown on screen
The Windows fuel gauge IC calibrates itself against the old cell's discharge curve. After a swap, the gauge's stored curve no longer matches the new cell's actual voltage-to-capacity profile, so the OS reports 25% when the cell is already near its low-voltage cutoff. Under full CPU plus display load, the voltage drop is sharper than under light use — triggering an immediate BMS shutdown before the gauge catches up. Complete two to three full discharge and charge cycles without interruption. By the third cycle the fuel gauge IC will have mapped the new cell's curve and the reported percentage will align with actual remaining capacity.