About this replacement
Sony VAIO PCG-SR Series — 11.1V Li-ion Replacement Battery (PCGA-BP2S)
This is an 11.1V 4400mAh (48.84Wh) lithium-ion battery replacing OEM part PCGA-BP2S. It fits the Sony VAIO PCG-SR1/BP, PCG-SR11K, PCG-SR17, PCG-SR17D, and over 70 additional SR-series notebook models. The cell matches the original connector pinout and BMS handshake required by the VAIO PCG-SR platform.
- PCG-SR platform compatibility: All covered SR-series models share the same 11.1V three-cell rail, identical physical connector, and the same BMS communication protocol — which is why one cell works across this wide model range without modification.
- Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on a PCG-SR unit. The BMS handshook correctly, charge termination triggered at the expected voltage ceiling, and protection cutoff activated cleanly under load.
- Post-install discharge cycle: After fitting this cell, run one full discharge to hibernate cutoff, then charge uninterrupted to 100%. This resets the BIOS battery learn cycle and clears the false health warning that appears after every cell swap on SR-series notebooks.
BIOS reporting poor battery health immediately after installing a new cell
The PCG-SR BIOS reads EEPROM data stored on the original cell and compares it against incoming charge cycles to estimate health. A new cell has no matching history in that register, so the BIOS flags it as degraded — even though the cell is new. This is not a battery fault. Run one full discharge to hibernate, then a full uninterrupted charge to 100%. After two to three cycles, the BIOS recalibrates its health estimate against the new cell's actual behaviour.
Laptop shuts off abruptly at 20–30% charge shown on screen
This happens when the cell cannot hold voltage above the BMS cutoff threshold under combined CPU and display load — even though the fuel gauge IC still shows remaining charge. The fuel gauge IC maps voltage curves from the old cell, so its percentage readout lags behind actual cell state. Under full load, voltage drops steeply and hits the BMS floor before the displayed percentage reaches zero. Run two full discharge-to-hibernate and full-charge cycles to let the fuel gauge IC relearn the voltage curve of the new cell, and the premature shutdowns should stop.