About this replacement
Lenovo Legion 5 17ACH6H Series — 15.36V Li-Polymer Replacement Battery (L20C4PC2)
This is a 15.36V, 5000mAh (76.8Wh) Li-Polymer replacement battery for the Lenovo Legion 5 17-inch gaming laptop. It fits the Legion 5 17ACH6H-82JY00GMMX and over 150 compatible Legion 5 variants across the ACH6, ITH6H, and related sub-series. OEM part numbers covered include L20C4PC2, L20M4PC2, L20L4PC2, L20D4PC2, SB11B53887, and SSB11B53884.
- Legion 5 17-inch platform fit: The ACH6H, ACH6, and ITH6H sub-series all share the same 15.36V four-cell battery architecture, connector pinout, and BMS handshake protocol — which is why one part number family covers all of them. Swapping between sub-variants does not affect BMS communication.
- Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on Legion 5 hardware. The BMS negotiated correctly, charge current stepped down properly at 95%, and there was no fault flag at the EC level during load transitions from idle to full CPU and GPU draw.
- Post-install calibration cycle: After fitting, run the laptop on battery until it hibernates at the low-voltage cutoff, then charge uninterrupted to 100% without using the machine. This resets the BIOS battery learn cycle and clears the inaccurate health warning that appears after every cell swap.
BIOS reporting poor battery health immediately after replacement
Lenovo's BIOS reads health data from EEPROM embedded in the battery pack — not from live cell measurements. When a new cell arrives, that EEPROM data does not match the charge history the BIOS expects to see, so it flags the battery as degraded or unknown. This is a data mismatch, not a fault with the replacement cell. Run one full discharge-to-hibernate cycle followed by an uninterrupted charge to 100%. After one or two complete cycles the BIOS learn cycle re-establishes baseline data and the health warning clears.
Laptop shuts off at 20–30% charge shown on screen
This happens when the fuel gauge IC has not yet calibrated against the new cell's actual voltage curve. The OS is reading a fuel map built from the old, degraded cell — so it thinks 25% remaining is safe when the new cell is already near its real low-voltage threshold under load. Under full CPU plus display draw on the Legion 5, voltage sag on a miscalibrated gauge hits the EC cutoff before the reported percentage reaches zero. Fix this by completing two full discharge-to-hibernate cycles followed by full charges — recalibrates the fuel gauge IC against the actual cell chemistry and the premature shutdowns stop.