About this replacement
Motorola Moto X Pro — 3.8V Li-Polymer Replacement Battery (HP6X / SNN5891A)
This 3.8V, 1550mAh Li-Polymer cell replaces the original HP6X / SNN5891A battery in the Motorola Moto X Pro and XT685 series handsets. It restores power to the display, processor, modem, and connectivity stack when the original cell has degraded or failed. Dimensions are 50.12 x 45.50 x 5.20mm — a direct physical match to the factory battery bay.
- Moto X Pro and XT685 series compatibility: The Pro, Pro+, and XT685 variants all share the same battery bay geometry and connector pinout, which is why a single cell covers the full range. Voltage and BMS communication lines are identical across these models.
- Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on an XT685 unit. The BMS handshake completed correctly, charge current tapered as expected near full capacity, and the fuel gauge IC accepted the new cell without error codes.
- First-cycle calibration on the Moto X Pro: On first use after installation, disable fast charging and complete one full discharge-to-charge cycle. This gives the fuel gauge IC a clean discharge curve to calibrate against before high-current charging pushes into an uncalibrated cell.
Sudden shutdown at 20–30% on the Moto X Pro after a cell swap
This happens when the fuel gauge IC still holds the discharge curve of the old, degraded cell. The new cell has a steeper voltage cliff under modem and display load — the IC predicts 20% remaining but the actual cell voltage collapses before that point. The phone interprets the voltage drop as a hard cutoff and shuts down instantly. One full discharge-to-charge cycle lets the coulomb counter relearn the new cell's actual behaviour and clears the shutdown.
OS reporting wrong battery percentage after replacement
The Moto X Pro's fuel gauge IC calibrates its percentage model to the cell it last tracked, not the new one. After swapping the HP6X cell, the IC may display erratic or frozen percentages — commonly jumping 10–15% in either direction. This is not a fault with the replacement cell. Drain the battery completely until the phone powers off, then charge uninterrupted to 100% — one full cycle resets the coulomb counter and aligns percentage reporting to the new cell's actual capacity.