About this replacement
Sony VAIO VGN-AX570G / VGN-BX Series — 11.1V Li-ion Replacement Battery (VGP-BPL4)
This 11.1V 8800mAh (97.68Wh) Li-ion battery replaces the VGP-BPL4, VGP-BPL4A, VGP-BPS4, and VGP-BPS4A across Sony VAIO VGN-AX and VGN-BX series laptops. It fits the VGN-AX570G, VGN-AX580G, VGN-BX143C, VGN-BX143CP, and over 50 additional VAIO models sharing this battery bay and connector. Capacity is 8800mAh — matched to the original specification.
- VGN-AX and VGN-BX platform fit: Sony used the same 11.1V battery rail, physical bay dimensions, and SMBus connector pinout across the VGN-AX and VGN-BX lines. Any model listing VGP-BPL4 or VGP-BPS4 as its OEM part number draws from the same electrical specification, so one cell covers the full range without adapter or modification.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on VAIO hardware. The BMS communicated state-of-charge correctly over SMBus, accepted charge from the OEM AC adapter without triggering a fault, and held voltage within spec at the discharge knee.
- First-cycle calibration on VAIO BX and AX laptops: After installing, run the laptop on battery until it reaches hibernate cutoff — do not plug in mid-cycle. Then charge uninterrupted to 100%. This gives the fuel gauge IC a full reference curve against the new cell and clears the inaccurate health warning BIOS displays after every cell swap.
BIOS reporting battery health as "poor" immediately after installation
Sony VAIO BIOS reads health status from EEPROM data stored in the battery's BMS — not from live cell measurements. When a new cell arrives, its EEPROM cycle count and rated capacity may not match what the BIOS expects from the previous battery's learned data. The system flags this mismatch as "replace battery" or "poor health" even though the cell is new. Running one full discharge-to-hibernate then a complete uninterrupted charge resets the learn cycle and brings the BIOS health indicator back to normal.
Laptop shuts down abruptly with 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 gauge loses accuracy at the low end, and the laptop hits the hardware undervoltage cutoff before the OS reaches 0%. Under combined CPU and display load, voltage drops faster than the uncalibrated gauge predicts. Run two full discharge-to-hibernate cycles with an uninterrupted charge to 100% between each — after that, the cutoff should align with the gauge reading at or below 5%.