About this replacement
Apple iPhone X — 3.82V Li-Polymer Replacement Battery (616-00351)
This 3.82V, 2700mAh lithium-polymer battery replaces the original Apple 616-00351 cell in the iPhone X. It fits all iPhone X variants including MQA62LL/A, MQA92LL/A, and MQA82LL/A. Swap it when the original cell no longer holds charge, triggers unexpected shutdowns, or fails health checks in iOS Settings.
- iPhone X fit confirmation: All iPhone X variants share the same single-cell Li-Polymer configuration, the same 96.50 × 57.20 × 4.22mm footprint, and the same 5-pin flex connector that carries both charge data and the fuel gauge IC signal. One cell fits the full model range.
- Bench tested on actual hardware: We cycled this cell through a full discharge and charge on an iPhone X logic board. The BMS handshake completed on the first cycle, and the charge IC accepted current without triggering a thermal fault or a USB-PD rejection event.
- Fuel gauge recalibration on first use: After installation, disable fast charging and run one complete discharge down to auto-shutdown, then charge to 100% on a standard 5W adapter. This lets the coulomb counter recalibrate its endpoint values against the new cell before high-current charging begins.
Sudden shutdown at 20–30% on the replacement cell
A fresh cell triggers this more often than a worn one because the fuel gauge IC still holds the discharge curve from the old battery. When the modem fires a high-draw burst — during a call, LTE handoff, or GPS lock — the new cell's voltage dips sharply at a state-of-charge the IC thinks is safe. The phone interprets that voltage drop as a hard cutoff and shuts down. One full discharge-to-shutdown cycle followed by a full charge resets the coulomb counter endpoint, and the shutdowns stop. If they persist past two cycles, check that the flex connector is fully seated — an intermittent contact causes identical symptoms.
iOS battery percentage jumping erratically after swap
The iPhone X reads state-of-charge through a fuel gauge IC on the battery flex, not a direct voltage measurement. When you install a new cell, that IC carries calibration data mapped to the old cell's internal resistance profile, not the new one. The result is percentage readings that jump forward or backward by 5–15% without a corresponding load change. Run two full cycles — discharge to auto-shutdown, then charge uninterrupted to 100% — and the IC rewrites its reference curve. After two cycles, percentage movement should track within 2–3% of actual state-of-charge under normal load.