About this replacement
HP EliteBook 865 G9 / ZBook Firefly 16 G9 — 11.58V Li-Polymer Replacement Battery (WP06XL)
This is an 11.58V, 6300mAh (72.95Wh) Li-Polymer battery that replaces the OEM WP06XL cell. It fits the HP EliteBook 865 G9 6H724UT, ZBook Firefly 16 G9 6B897EA, ZBook Firefly 16 G9 6Q411UT, EliteBook 860 G9 6K687PA, and over 90 additional HP business laptop configurations sharing the same battery slot and connector pinout.
- EliteBook 860/865 G9 and ZBook Firefly 16 G9 compatibility: These models share the same three-cell Li-Polymer pack format, 11.58V nominal rail, and SMBus BMS handshake. One cell covers the whole group because HP standardised the connector and communication protocol across this generation of 14–16 inch business ultrabooks.
- Bench tested on actual hardware: We ran this cell on an EliteBook 865 G9 and confirmed the BMS completed a full charge cycle without tripping an over-voltage fault. Charge acceptance held consistent across multiple cycles and the SMBus communication registered without error codes.
- BIOS battery learn cycle after installation: After fitting this cell, run the laptop on battery until it hibernates at the low-voltage cutoff, then charge uninterrupted to 100%. This forces the BIOS to complete one learn cycle against the new cell chemistry and clears the inaccurate health warning that appears after every cell swap on HP EliteBook G9 hardware.
Why the EliteBook 865 G9 reports poor battery health immediately after a cell swap
The HP BIOS stores battery health data in EEPROM and compares the new cell's reported capacity against the degraded profile it recorded from the old cell. A fresh cell with full capacity reads as mismatched, so the BIOS flags it as unknown or unhealthy on first boot. This is not a fault with the replacement cell. Running one complete discharge-to-hibernate followed by an uninterrupted charge to 100% resets the learn cycle. After two to three full cycles the BIOS recalibrates and the health warning clears.
Laptop shuts down at 20–30% charge shown on the gauge
This happens when the fuel gauge IC has not yet calibrated against the new cell's actual discharge curve. The percentage readout is still mapped to the old cell's degraded profile, so the displayed figure and the real cell voltage fall out of sync. Under full CPU plus display load, the actual cell voltage hits the BMS cutoff threshold while the gauge still shows 20–30%. Run two full discharge-to-hibernate and charge-to-100% cycles to let the fuel gauge IC relearn the voltage curve. After calibration the shutdown should align with readings below 5%.