HP ProBook 4435s Compatible Battery 11.1V 4400mAh HSTNN-Q87C

HP ProBook 4435s / 4530s Series — 11.1V Li-ion Replacement Battery (HSTNN-Q87C-4)

This is an 11.1V 4400mAh (48.84Wh) lithium-ion battery for the HP ProBook 4435s, 4436s, 4530s, and 4535s. It replaces a wide range of OEM part numbers including HSTNN-Q87C-5, HSTNN-DB2R, PR06, PR09, and 633805-001. The connector and BMS handshake match the original HP spec for these ProBook models.

• ProBook 4435s / 4436s / 4530s / 4535s compatibility: These four models share the same battery bay dimensions, the same 11.1V three-cell series configuration, and the same SMBus communication protocol to the BIOS — that's why one battery part number covers all of them.
• Bench tested on actual hardware: We ran this cell on a ProBook 4530s and monitored the BMS handshake at startup. The BIOS recognised the battery immediately, the charge IC accepted a full charge cycle, and the protection circuit triggered correctly at the low-voltage cutoff threshold.
• First-cycle conditioning on ProBook BIOS: After fitting this battery, run the laptop on battery power until it hibernates at the low-voltage cutoff — do not interrupt it. Then charge uninterrupted to 100%. This resets the BIOS battery learn cycle and clears the inaccurate health warning that appears after every cell swap on ProBook firmware.

Why the ProBook 4435s BIOS reports poor battery health immediately after a swap

The ProBook BIOS reads battery health from EEPROM data stored inside the battery's fuel gauge IC — not from live voltage measurements. When a new cell arrives, that EEPROM contains factory default values that don't match a fully conditioned charge cycle, so the BIOS flags it as degraded or unknown. This is firmware behaviour, not a fault with the replacement cell. Running one complete discharge-to-hibernate followed by an uninterrupted charge to 100% allows the BIOS to write fresh cycle data to the EEPROM. After one or two full learn cycles, the health indicator updates to normal.

ProBook shuts down at 20–30% charge shown on screen

This happens when the fuel gauge IC hasn't calibrated against the new cell yet. The percentage shown on screen is based on old capacity data, so the displayed figure and the actual cell voltage are out of sync. Under full CPU and display load, the cell hits its real voltage floor before the OS expects it — the BIOS triggers an emergency shutdown to protect the cell. Run two full discharge-to-hibernate and charge-to-100% cycles back to back. After that, the fuel gauge recalibrates and the cutoff aligns with the displayed percentage; the shutdown threshold on these ProBook models sits at approximately 10.5V under load.