About this replacement
Sony VAIO VPC-W111XX Series — 11.1V Li-ion Replacement Battery (VGP-BPS18)
This is an 11.1V, 4400mAh (48.84Wh) Li-ion replacement battery for the Sony VAIO VPC-W111XX netbook series. It fits VPC-W111XX/P, VPC-W111XX/PC, VPC-W111XX/T, VPC-W111XX/W, and over 98 additional VAIO W-series models. OEM part numbers VGP-BPS18 and VGP-BPL18 cross-reference directly to this cell.
- VAIO VPC-W111XX series fit: All VPC-W111XX variants share the same 11.1V three-cell rail, identical connector pinout, and BMS handshake protocol — which is why one cell covers the entire W-series lineup without modification.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on a VPC-W111XX unit. The BMS negotiated correctly with the VAIO's charge controller, held voltage above the low-cutoff threshold through full discharge, and accepted a complete charge cycle without interruption or fault flags.
- First-cycle calibration on the VAIO W series: After installing, run one full discharge until the laptop hibernates on its own, then charge uninterrupted to 100%. This forces the BIOS battery learn cycle to reset against the new cell's actual capacity and clears the inaccurate health warning that appears after every cell swap.
BIOS reporting poor battery health immediately after fitting a new cell
The VAIO's BIOS reads health data stored in the battery's EEPROM, not the live cell voltage. When a new cell is installed, the EEPROM contains factory-default data that doesn't match the BIOS's stored discharge history for the old pack. The system flags this mismatch as a fault. Running one full discharge-to-hibernate followed by an uninterrupted charge to 100% resets the learn cycle and rewrites the BIOS's reference data. After two to three cycles, the health reading normalises.
VAIO shutting down at 20–30% charge shown on screen
This happens when the fuel gauge IC hasn't yet calibrated against the new cell's discharge curve. The IC carries forward voltage-to-capacity mapping from the old, degraded pack. Under combined CPU and display load, the new cell hits a voltage cliff that the uncalibrated gauge misreads as 20–30% remaining. The laptop shuts down because actual cell voltage has dropped below the safe cutoff while the gauge still shows capacity. Force a full discharge to hibernate, then charge to 100% without interruption — the fuel gauge recalibrates at that floor and ceiling, and the reported percentage will track accurately from the next cycle onward.