HP 40Q85UA Chromebook Replacement Battery 7.7V 3950mAh

HP Chromebook X2 11 Series — 7.7V Li-Polymer Replacement Battery (DS02032XL)

This is a 7.7V, 3950mAh (30.42Wh) Li-Polymer battery built to fit the HP Chromebook X2 11 detachable tablet-notebook series and related HP notebook models including 40Q85UA, 3G0N5UA, DA0013DX, and DA0023DX. OEM part numbers DS02XL, HSTNN-OB1Z, and M38086-005 all cross to this cell. The connector and BMS handshake match the original DS02032XL specification.

• Chromebook X2 11 tablet-base compatibility: The X2 11 detaches the display from the keyboard base, and the battery sits inside the display unit. All models in this series share the same 7.7V two-cell Li-Polymer configuration, slim 3.50mm profile, and DS02XL BMS data — which is why this cell fits every variant on the list.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a Chromebook X2 11 unit. The BMS accepted the cell without error flags, the charge controller stepped correctly through CC and CV phases, and the fuel gauge reported capacity within expected tolerance after two full cycles.
• Post-install calibration on ChromeOS: After fitting this cell, let the device discharge fully until it shuts down on its own — do not force a hard power-off. Then charge uninterrupted to 100% with the lid closed. This resets the ChromeOS fuel gauge IC against the new cell and clears the inaccurate health warning that appears after every cell swap.

Why ChromeOS flags a new battery as poor health immediately after swap

The Chromebook's embedded controller reads EEPROM data stored on the original cell — cycle count, rated capacity, and charge history. When a new cell arrives with a clean EEPROM, the EC compares it against the laptop's learned baseline and flags a mismatch as degraded health. This is a firmware read error, not a physical fault with the replacement cell. Running one full discharge-to-shutdown followed by an uninterrupted charge to 100% writes fresh data to the EC and clears the warning permanently.

Laptop shuts down at 20–30% charge shown on the battery indicator

This happens when the fuel gauge IC has not yet calibrated against the new cell's actual voltage curve. The gauge is still using the old cell's discharge profile, so it misjudges where the voltage cliff is and triggers a protective shutdown early. The fix is two to three full discharge-charge cycles — each one teaches the gauge where the new cell actually hits its lower cutoff voltage, typically around 6.0V under load for a 7.7V two-cell pack. After the third cycle, the reported percentage at shutdown should align with actual remaining capacity.