About this replacement
HP EliteBook 850 G1 — 11.1V Li-Polymer Replacement Battery (HSTNN-DB4Q)
This 11.1V, 4500mAh (49.95Wh) Li-Polymer battery fits the HP EliteBook 850 and EliteBook 850 G1 series. It replaces OEM part numbers including CM03XL, CO06XL, and HSTNN-IB4R. Use it when the original cell no longer holds a charge or when BIOS flags battery health as critical.
- EliteBook 850 and Z-series compatibility: These notebooks share the same 11.1V power rail, six-pin BMS connector, and EEPROM handshake protocol — which is why a single cell SKU covers the full EliteBook 850 G1 range and several Z-series models. The BMS communicates state-of-charge data directly to the BIOS over SMBus.
- Bench tested on actual hardware: We ran this cell on an EliteBook 850 G1 under combined CPU and display load. The BMS held the voltage rail above 10.2V through discharge and did not trigger an unexpected cutoff. BIOS battery status updated correctly after one full charge cycle.
- First-cycle reset after install: After fitting this battery, 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 and clears the inaccurate health warning that appears after every cell swap.
BIOS reporting battery health as poor immediately after replacement
The EliteBook 850 G1 BIOS stores charge history and health metrics in the old cell's EEPROM. When a new cell is installed, the BIOS compares its stored data against a blank EEPROM and flags the health as unknown or poor. This is not a fault with the replacement cell — it is a data mismatch. Running the battery learn cycle (full discharge to hibernate, then an uninterrupted charge to 100%) overwrites the stored baseline with data from the new cell. After two full cycles, BIOS health reporting normalises.
Laptop shutting down at 20–30% charge shown on screen
This happens when the fuel gauge IC has not yet calibrated against the new cell's discharge curve. The IC uses data from the previous cell and predicts cutoff too early — the display reads 25% but the cell voltage has already dropped below the BMS floor under full CPU and display load. It is not a faulty battery. Run two complete discharge-to-hibernate and full-charge cycles so the fuel gauge IC re-maps the voltage cliff for this specific cell. After calibration, the gauge will read accurately down to the true cutoff at approximately 9.9V.