About this replacement
HP ProBook 640 G1 — 10.8V Li-ion Replacement Battery (CA06XL)
This is a 10.8V, 4400mAh (47.52Wh) Li-ion replacement battery for the HP ProBook 640 G1 and the broader ProBook 640, 645, and 655 notebook lines. It replaces OEM part CA06XL and cross-references HSTNN-IB4W, HSTNN-LB4X, 718755-001, and related HP part numbers. Install it when the original cell no longer holds charge or the laptop shuts down unexpectedly under load.
- ProBook 640 / 645 / 655 series fit: These models share the same 10.8V battery rail, physical connector pinout, and BMS handshake protocol — which is why one cell covers the full range. The laptop's EC communicates with the battery's protection circuit over SMBus; mismatched cells from other ProBook generations will fail that handshake and refuse to charge.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a ProBook 640 G1 unit. The BMS passed the SMBus health query correctly, the OS fuel gauge registered capacity within expected tolerance, and the charge circuit completed a full cycle to 100% without fault codes.
- First-cycle calibration after install: After fitting this battery, run the laptop down to hibernate-cutoff on normal use — do not force-drain it — then charge it uninterrupted to 100% without logging off. This gives the BIOS battery learn cycle a clean baseline against the new cell and clears the inaccurate health warnings that appear after every cell swap.
BIOS reporting poor battery health immediately after replacement
The ProBook 640 G1 BIOS stores battery health data from the previous cell in its embedded controller memory. When a new cell is installed, the EC compares live readings against that stale EEPROM data and flags a mismatch as degraded health. This is not a fault with the new battery. Run one full discharge-to-hibernate followed by an uninterrupted charge to 100% — the BIOS battery learn cycle will rewrite its baseline and the warning clears on the next boot.
Laptop shuts down at 20–30% charge shown on screen
This is a voltage cliff symptom: the fuel gauge IC reads state-of-charge from a cell model calibrated to the old battery's wear curve, not the new cell's actual chemistry profile. Under full CPU and display load, the real cell voltage drops faster than the IC predicts, triggering a hard shutdown before the displayed percentage reaches zero. It typically resolves after two to three full discharge-and-charge calibration cycles. If the shutdown persists past three cycles, check that the charge completed to a full 10.8V terminal voltage each time.