About this replacement
Sony VAIO Fit 15A — 15V Li-Polymer Replacement Battery (VGP-BPS40)
This is a 15V, 3150mAh (47.25Wh) lithium-polymer replacement battery for the Sony VAIO Fit 15A and its SVF15N and SVF14N variants. It fits the ultra-thin chassis where the original VGP-BPS40 cell sits flush across the base. Use it when the factory battery no longer sustains a charge through a normal work session.
- VAIO Fit 15A and 14A compatibility: Sony's Fit A-series shares the VGP-BPS40 cell across both screen sizes — same 15V rail, same flat Li-Polymer pack dimensions, same BMS handshake protocol. SVF15N18PW, SVF15N13CW, and the 14A variants all draw from identical battery firmware.
- Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on the Fit 15A platform. The BMS handshake completed without error flags, charge acceptance hit rated capacity, and the protection circuit tripped correctly at low-voltage cutoff.
- Post-install calibration on the VAIO Fit 15A: 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 the VAIO firmware throws after every cell swap.
Why the VAIO Fit 15A reports poor battery health immediately after a cell swap
The VAIO firmware stores charge history and cycle count in the old cell's EEPROM. When a new cell goes in, the BIOS reads no stored data and flags the battery as degraded or unknown. This is a data mismatch — not a fault with the replacement cell. Running the battery learn cycle (full discharge to hibernate, then a full uninterrupted charge) writes fresh calibration data and clears the health warning. After two to three full cycles, the reported health status normalises.
VAIO Fit 15A shutting down at 20–30% charge remaining
This happens when the fuel gauge IC hasn't yet calibrated against the new cell's voltage curve. The OS reads the old curve, assumes the cell is near-empty, and triggers shutdown — even though usable capacity remains. The fix is a full discharge-to-hibernate cycle followed by a complete charge to 100%, repeated twice. After that, the fuel gauge maps the correct curve and the remaining percentage tracks accurately down to the real low-voltage cutoff near 12V.