About this replacement
Acer Aspire S 13 S5-371 — 11.55V Li-Polymer Replacement Battery (AP15O5L)
This is an 11.55V, 4600mAh (53.13Wh) lithium-polymer battery for the Acer Aspire S 13 series ultrabook. It replaces OEM part numbers AP15O5L, AP1505L, AP1503K, and AP15O3K. Fits the S5-371 chassis and all sub-models on that platform.
- S5-371 platform compatibility: Every S5-371 variant — including the 52JR and 53NX — runs the same 11.55V three-cell Li-Polymer architecture with a shared connector pinout and BMS handshake protocol. One cell covers the full range.
- Bench tested on actual hardware: We cycled this cell on an S5-371 unit and confirmed the BMS completes charge handshake correctly, holds voltage above 10.8V at full CPU and display load, and does not trigger an early cutoff under sustained draw.
- First-cycle calibration on the S5-371: After installing, run one full discharge until the laptop hibernates on its own, then charge uninterrupted to 100%. This resets the BIOS battery learn cycle and clears the inaccurate health warning the S5-371 displays after every cell swap.
BIOS reporting poor battery health immediately after fitting a new cell
The S5-371 BIOS reads health data stored in the old cell's EEPROM before the new cell has completed a learn cycle. Until calibration runs, the firmware compares current state-of-charge against stale reference data and flags the battery as degraded. This is not a fault with the replacement cell. One full discharge-to-hibernate followed by an uninterrupted charge to 100% gives the BIOS a fresh reference point and clears the warning on next boot.
Laptop shuts down at 20–30% shown on the OS fuel gauge
This happens when the fuel gauge IC has not yet calibrated against the new cell's actual voltage curve. The gauge shows 20–30% remaining, but the cell voltage has already dropped below the BMS cutoff threshold — typically around 9.9V under load on this platform. The system shuts down to protect the cell even though the percentage looks safe. Run two to three full discharge-to-charge cycles and the OS gauge will align with real cell voltage. After calibration, the shutdown point moves back to below 5% as expected.