About this replacement
HP ProBook 640 G2 Series — 11.4V Li-Polymer Replacement Battery (CI03)
This is an 11.4V, 3400mAh (38.76Wh) Li-Polymer replacement battery for the HP ProBook 640 G2, 645 G2, 650 G2, and 655 G2. It replaces OEM part numbers CI03, CI03XL, HSTNN-UB6Q, HSTNN-LB6T, and over a dozen related HP part numbers. The cell fits the same bay and uses the same connector as the original HP unit.
- ProBook 640/645/650/655 G2 compatibility: These four models share the same 11.4V three-cell Li-Polymer platform, identical battery bay dimensions, and the same SMBus BMS handshake. A battery validated on the 640 G2 communicates the same way across the full G2 quartet without hardware modification.
- Bench tested on actual hardware: We ran this cell on a ProBook 650 G2 and monitored the BMS initialisation sequence over SMBus. The controller accepted the cell, reported charge state correctly, and the protection circuit tripped normally at low-voltage cutoff without requiring a manual reset.
- First-cycle BIOS calibration: After installation, run one full discharge to hibernate cutoff, then charge uninterrupted to 100%. This forces the ProBook's BIOS battery learn cycle to index against the new cell and clears the inaccurate health warning that almost always appears after a cell swap.
Why the ProBook 640 G2 BIOS flags a new battery as "poor health"
HP's BIOS reads battery health from EEPROM data embedded in the old cell. When a replacement cell arrives, that EEPROM record is blank or contains generic factory values, so the BIOS compares them against internal thresholds and fails the check. This is not a fault with the replacement cell — it is a mismatch between stored cycle data and the new chemistry baseline. Running the full discharge-to-charge calibration cycle rewrites the learn data and the warning clears on the next boot.
ProBook shuts down at 20–30% charge shown on screen
When the CPU and display are both under full load, current draw spikes sharply. If the fuel gauge IC has not yet calibrated to the new cell, it overestimates remaining capacity by 20–30%. The cell voltage actually hits the low-voltage cliff while the OS still shows charge remaining, triggering an abrupt shutdown. Run two or three full discharge-and-recharge cycles so the fuel gauge IC can map the actual voltage curve of the replacement cell. After calibration, the OS percentage and real cell voltage align and the premature shutdowns stop.