About this replacement
Acer Swift 1 SF113-31 Series — 11.25V Li-Polymer Replacement Battery (AP16A4K)
This is an 11.25V, 3700mAh (41.63Wh) Li-Polymer battery for the Acer Swift 1 SF113-31 ultrabook series. It fits the SF113-31-P2VH, SF113-31-P87M, SF113-31-P1YS, SF113-31-P6YX, and over 160 additional SF113-31 variants. OEM cross-references include AP16A4K, KT.00304.003, and KT.00304.007.
- SF113-31 series compatibility: All SF113-31 variants share the same 11.25V three-cell architecture, connector pinout, and BMS handshake protocol. The AP16A4K part number covers the full production run of this chassis — Acer did not change the battery specification mid-run on this series.
- Bench tested on actual hardware: We ran this cell on an SF113-31 unit and confirmed the BMS negotiated charge acceptance correctly at each voltage step. The protection circuit tripped at the expected low-voltage cutoff and recovered cleanly on reconnect.
- Post-install calibration on the Swift 1: After fitting this battery, run one full discharge down 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 chassis.
BIOS reporting poor battery health immediately after fitting a new cell
The SF113-31 BIOS reads health data from EEPROM fields written by the original cell during its first charge cycles. A new cell arrives with blank or factory-default EEPROM values, so the BIOS flags it as degraded — even though the cell is new. This is not a fault with the replacement battery. Running one full discharge-to-hibernate followed by an uninterrupted charge to 100% writes new baseline data and clears the warning. After two to three cycles the BIOS health indicator will update correctly.
Swift 1 shutting down abruptly 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 reported percentage and the real cell voltage fall out of sync, and the laptop hits the hardware low-voltage cutoff before the OS gauge reaches zero. It is most pronounced under combined CPU and display load, which pulls the cell voltage down sharply. Run two full discharge-to-hibernate and charge-to-100% cycles — after that the fuel gauge IC recalibrates and the shutdowns stop. Confirm calibration is complete when the gauge reads below 10% without triggering an unexpected shutdown.