About this replacement
Apple iPhone X — 3.82V Li-Polymer Replacement Battery (616-00351)
This 3.82V, 3150mAh (12.03Wh) Li-Polymer battery is a direct cell replacement for the Apple iPhone X. It fits all iPhone X variants, including MQA62LL/A, MQA92LL/A, and MQA82LL/A. The OEM part number is 616-00351, matching Apple's original specification for this device.
- iPhone X compatibility: All iPhone X variants share the same battery bay geometry, connector pinout, and BMS handshake protocol. The 616-00351 cell format and voltage rail are consistent across every regional SKU of this model.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on an iPhone X unit. The BMS accepted the cell without error flags, fuel gauge IC synced after one full cycle, and charge IC negotiation completed normally under both standard and fast charge protocols.
- First-cycle fast charge tip: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC recalibrate against the new cell's discharge curve before high-current fast charging pushes current into an uncalibrated cell.
Why the iPhone X reports wrong battery percentage after a cell swap
The iPhone X uses a coulomb counter inside the power management IC to track state of charge. That counter was calibrated to the original cell's discharge curve over hundreds of cycles. A new cell has a different internal resistance profile, so the counter's reference points are off from the start. The fix is one full discharge to automatic shutoff followed by a complete charge to 100% — this resets the fuel gauge's anchor points against the new cell.
Sudden shutdown at 20–30% remaining on the replacement cell
This happens because the fuel gauge IC still references the old cell's voltage-to-capacity curve. At high load — modem transmitting, screen at full brightness — the new cell's voltage briefly dips below the shutdown threshold even though capacity remains. The power management IC reads that as a critically low cell and cuts power. Run one full calibration cycle first, then check if shutdowns persist; if they do, verify the battery connector is fully seated, as a loose contact raises contact resistance and amplifies voltage sag under load.