About this replacement
HP Pavilion 15-CS1004NA — 15.4V Li-Polymer Replacement Battery (HSTNN-IB8S)
This is a 15.4V, 4350mAh (66.99Wh) lithium-polymer replacement battery for the HP Pavilion 15-CS series notebook. It fits the 15-CS1004NA and over 40 closely related CS1000-range models. The OEM part numbers covered include HSTNN-IB8S, L32535-141, L32535-1C1, L32654-005, and LG04XL.
- Pavilion 15-CS series compatibility: Every model in this CS1000 range uses the same 15.4V four-cell LG04XL cell stack, identical connector pinout, and the same BMS handshake protocol. One battery covers the full group without modification.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a Pavilion 15-CS unit. The BMS completed full charge termination at 16.8V, and the protection circuit held under sustained CPU and display load without tripping.
- Post-install calibration on the Pavilion 15-CS: After fitting this battery, run the laptop down to hibernate-cutoff on a single discharge, then charge uninterrupted to 100%. This resets the BIOS battery learn cycle and clears the inaccurate health warning the CS series throws after every cell swap.
BIOS reporting poor battery health immediately after fitting a new cell
The Pavilion 15-CS BIOS reads health data from EEPROM embedded in the battery's BMS — not from live cell measurements. When a new cell arrives, that EEPROM contains factory baseline data the BIOS hasn't yet validated against actual charge cycles. The system flags it as unknown or degraded because it has no learned history for the new pack. One complete discharge-to-hibernate followed by a full uninterrupted charge gives the BIOS enough data to update its health register correctly.
Laptop shuts down abruptly at 20–30% shown on the fuel gauge
This happens when the fuel gauge IC is still calibrated to the old cell's voltage curve. The new lithium-polymer cell has a steeper voltage drop in the lower state-of-charge range, so the gauge misreads remaining capacity and reports 20–30% while the cell is already near cutoff voltage. The laptop shuts down because the cell can't sustain voltage under combined CPU and display load, not because of a battery fault. Run two full calibration cycles — discharge to hibernate, charge to 100% — and the fuel gauge IC will re-map to the new cell's actual curve.