About this replacement
HP ProBook 645 G4 — 11.4V Li-ion Replacement Battery (HSTNN-IB8B)
This is an 11.4V, 3300mAh (37.62Wh) Li-ion replacement battery for the HP ProBook 645 G4 notebook. It fits the standard battery bay and connects via the original three-pin power and data connector. Covers ProBook 645 G4 variants including 3UP61EA and 3UP62EA.
- ProBook 645 G4 compatibility: All ProBook 645 G4 variants run the same 11.4V three-cell rail and use the same BMS handshake protocol over the SMBus data line. The CD03XL and HSTNN-IB8B share the same connector pinout and communicate identically with the EC firmware — no adapter or modification needed.
- Bench tested on actual hardware: We ran this cell on a ProBook 645 G4 unit under combined CPU and display load. The BMS held voltage above 10.2V at full draw and stepped through charge stages cleanly from CC to CV without fault codes.
- Post-install calibration on the ProBook 645 G4: After fitting, run one full discharge until the laptop hibernates, then charge uninterrupted to 100% without interruption. This resets the BIOS battery learn cycle and clears the inaccurate health warning that appears after every cell swap.
BIOS reporting battery health as poor after fitting a new cell
The HP ProBook 645 G4 BIOS reads health data from EEPROM registers on the battery's gas gauge IC, not from live cell measurements. When a new cell arrives, those registers contain factory defaults that don't match the BIOS's learned discharge curve from the old battery. The BIOS flags this mismatch as poor health immediately after installation, even on a full cell. Running one complete discharge-to-hibernate followed by a full uninterrupted charge rewrites the learned data and clears the warning on the next boot.
ProBook 645 G4 shutting down at 20–30% charge shown on screen
This happens when the cell voltage drops below the EC's cutoff threshold under full CPU plus display load, even though the fuel gauge IC still reads 20–30% remaining. The fuel gauge hasn't yet mapped the new cell's actual voltage-to-capacity curve, so it misjudges remaining capacity at high draw. The cell hits the voltage cliff — typically around 10.0V under load — and the EC forces an immediate shutdown to protect the hardware. Two to three full calibration cycles bring the fuel gauge IC back into alignment and stop the early shutdowns.