HP ZBook x2 DN04XL Replacement Battery 15.4V 4500mAh

HP ZBook x2 G4 — 15.4V Li-Polymer Replacement Battery (DN04XL)

This is a 15.4V, 4500mAh (69.3Wh) lithium-polymer replacement battery for the HP ZBook x2 and ZBook x2 G4 detachable mobile workstation. It replaces OEM part numbers DN04XL, HSTNN-DB7P, 856301-2C1, 856843-850, and 856543-855. If the original cell has degraded and the system no longer holds a charge under workstation loads, this cell restores full capacity.

• ZBook x2 and x2 G4 fitment: Both the standard ZBook x2 and the G4 revision use the same DN04XL battery bay, connector pinout, and BMS handshake protocol. One cell covers both generations.
• Bench tested on actual hardware: We ran this cell through charge initiation, BMS communication handshake, and load cycling under CPU and display draw. The BMS accepted the cell, reported state-of-charge correctly, and the protection circuit held voltage within spec across the discharge curve.
• First-cycle recalibration on the ZBook x2: After installing, run one full discharge to hibernate cutoff, then charge uninterrupted to 100%. This forces the BIOS battery learn cycle to reset against the new cell's actual capacity and clears the inaccurate health warning that appears on first boot after any cell swap.

Why the ZBook x2 shuts down at 20–30% after a battery swap

The ZBook x2 stores discharge curve data in EEPROM from the previous cell. When a new cell goes in, that stored curve no longer matches the actual voltage behaviour of the replacement chemistry. Under full CPU plus display load, the BIOS hits a voltage floor it recognises as empty — even though the gauge still shows 20–30%. Running one full discharge-to-hibernate and one uninterrupted full charge resets the learned curve and eliminates the premature shutdown.

BIOS showing 0% or "unknown battery" immediately after installation

This happens because the fuel gauge IC on the new cell holds EEPROM data that does not yet match what the HP firmware expects after initialisation. The system cannot read a valid state-of-charge, so it reports 0% or flags the battery as unknown rather than displaying actual charge level. Connect the AC adapter and allow the cell to charge without interruption to 100% — this triggers the BIOS battery learn cycle and writes fresh calibration data to the fuel gauge IC. After one complete charge-discharge cycle, the reading stabilises and the unknown flag clears.