About this replacement
HP Pavilion 15-CX Series — 11.55V Li-Polymer Replacement Battery (SR03XL)
This is an 11.55V, 4000mAh (46.2Wh) lithium-polymer replacement battery for the HP Pavilion 15-CX series, including the 15-CX0058WM, 15-CX0071TX, and 15-CX0061TX. It replaces OEM part numbers SR03XL, HSTNN-IB8L, L08934-1B1, and L08855-855. Swap it in when the original cell no longer holds a charge or fails to register with the OS.
- Pavilion 15-CX series fit: The CX line uses a shared battery bay geometry, connector pinout, and BMS handshake across its variants. The SR03XL communicates cell data to HP's EC firmware over the SMBus interface — the same protocol used across the full CX platform, which is why one part number covers this many models.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a Pavilion 15-CX unit. The BMS negotiated correctly with the EC firmware, the fuel gauge IC initialised without error codes, and the charge controller reached full termination voltage at 12.6V without interruption.
- Post-install calibration on the CX platform: After fitting, run the laptop down to hibernate-cutoff under normal load, then charge uninterrupted to 100%. This forces the fuel gauge IC to recalibrate against the new cell and clears the inaccurate battery health warning the HP BIOS posts after every cell swap.
BIOS reporting poor battery health immediately after fitting the SR03XL
HP's EC firmware reads EEPROM data stored on the old cell and caches it. When a new cell is installed, that cached data conflicts with the fresh cell's reported state, triggering a false "poor health" or "consider replacing" warning in BIOS and Windows Battery Report. This is not a fault with the replacement cell — it is a calibration state. Run one full discharge to hibernate-cutoff, then a full uninterrupted charge to 100%. After two to three cycles, the fuel gauge IC rewrites its learned parameters and the BIOS warning clears.
Laptop shutting down at 20–30% charge shown on screen
This happens when the fuel gauge IC has not yet mapped the new cell's voltage curve. Under combined CPU and display load, the cell voltage drops faster than the uncalibrated gauge predicts, and the EC triggers a hard shutdown before the displayed percentage reaches zero. The gauge is reading a learned curve from the old cell, not the actual new one. Run two full discharge-to-hibernate and full-charge cycles — after that, the IC recalculates the voltage cliff point for the SR03XL chemistry and the shutdowns stop. Confirm the fix by watching cell voltage hold above 10.8V at the 20% mark under load.