About this replacement
Acer Aspire Switch Alpha 12 / SA5-271 — 7.6V Li-Polymer Replacement Battery (AP16B4J)
This is a 7.6V, 4450mAh (33.82Wh) Li-Polymer replacement battery for the Acer Aspire Switch Alpha 12 and SA5-271 2-in-1 hybrid devices. It also fits Switch 5 variants including the SW512-52P-50Q and SW512-52P-75HB. OEM part AP16B4J cross-references to KT.00204.003, NT.LCDAA.014, and NT.LCDEK.002.
- Switch Alpha 12 and Switch 5 compatibility: These models share the same slim Li-Polymer cell format, 7.6V nominal rail, and BMS connector pinout. The AP16B4J part number spans both the Alpha 12 and Switch 5 lines because Acer kept the battery architecture consistent across the SA5 and SW512 chassis revisions.
- Bench tested on actual hardware: We ran this cell on an SA5-271 unit and confirmed the BMS handshake completed without fault codes. The charge controller accepted the cell immediately, and the fuel gauge IC began tracking state-of-charge from the first cycle.
- Post-install calibration on the Switch Alpha 12: After fitting this cell, let the device discharge fully to hibernate cutoff, then charge uninterrupted to 100% without interruption. This resets the BIOS battery learn cycle and clears the inaccurate health warning that appears in Acer Care Center after every cell swap.
BIOS reporting battery health as poor immediately after replacement
The Switch Alpha 12 BIOS reads health data stored in the old cell's EEPROM and flags any new cell as degraded until a learn cycle updates that record. This is a firmware behaviour, not a fault with the replacement cell. The fix is one full discharge-to-hibernate followed by an uninterrupted charge to 100%. After that cycle, the BIOS recalculates health against the new cell's actual charge curve and the warning clears.
Laptop shuts down at 20–30% remaining after battery swap
This happens because the fuel gauge IC is still calibrated to the old cell's discharge curve. When the Switch Alpha 12 is under combined CPU and display load, the new cell's voltage profile differs enough that the gauge reports a false low-battery threshold. The device hits the shutdown voltage floor before the displayed percentage reaches zero. Run two full discharge-to-hibernate cycles back-to-back and the gauge IC relearns the new cell's voltage cliff — shutdowns at false percentages stop after the second calibration cycle.