About this replacement
HP Pavilion X360 15-BK150SA — 11.1V Li-ion Replacement Battery (WA03XL)
This is a 11.1V, 3950mAh (43.85Wh) Li-ion replacement battery for the HP Pavilion X360 15-BK150SA convertible notebook. It also fits a wide range of Pavilion X360 15 variants, including the 15-bk102ng and 15-br041nr. It replaces OEM part numbers WA03XL, HSTNN-LB7T, and 916367-421, among others.
- Pavilion X360 15 compatibility: These 15-BK and 15-BR models share the same three-cell Li-ion pack configuration, voltage rail, and connector pinout. The BMS handshake protocol and EEPROM data structure are consistent across this generation, so one cell fits all of them without modification.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the X360 platform and monitored BMS communication. The protection circuit responded correctly to charge cutoff at full capacity and to low-voltage cutoff under load — no rogue trip events recorded.
- Post-install calibration on the X360: After fitting this battery, run the laptop down to hibernate-cutoff under normal use — do not force it. Then charge uninterrupted to 100% without using the machine. This resets the BIOS battery learn cycle and clears the inaccurate health warning that appears after every cell swap on this platform.
Laptop shutting down at 20–30% shown on the Pavilion X360
This happens when the fuel gauge IC still holds calibration data from the old, degraded cell. The new cell's voltage curve does not match what the IC expects, so the system sees a steep voltage cliff and triggers an emergency shutdown well before the actual charge is gone. The fix is a full discharge-to-hibernate cycle followed by a full uninterrupted charge — repeated two to three times. After those calibration passes, the reported percentage will track the actual cell state correctly.
BIOS reporting wrong Wh rating after battery swap
The HP BIOS reads Wh rating from the cell's EEPROM, not from live measurement. If the EEPROM in the replacement cell carries a different factory-programmed rated capacity than the original, the system info screen will show a figure that does not match the label on the battery. This is an EEPROM data difference, not a fault. Actual charge capacity is determined by the cell chemistry — 43.85Wh in this case. To confirm, check the battery report in Windows: run powercfg /batteryreport in an elevated command prompt and compare the Design Capacity to the Full Charge Capacity after two calibration cycles.