About this replacement
Apple iPhone 8 Plus — 3.82V Li-Polymer Replacement Battery (616-00367)
This is a 3.82V, 2900mAh Li-Polymer battery for the Apple iPhone 8 Plus (A1864, MQ8F2LL/A and related variants). It replaces the original cell when the phone can no longer hold adequate charge due to age or wear. OEM part number 616-00367 confirms direct fitment to the 8 Plus chassis — not the standard iPhone 8.
- iPhone 8 Plus chassis compatibility: The 8 Plus uses a physically larger cell than the standard iPhone 8 — different dimensions (110.00 × 49.20 × 3.65mm), different OEM part number, different connector orientation. Mixing the two causes fitment failure or BMS handshake errors. This cell matches the 8 Plus specifically.
- Bench tested on actual hardware: We ran this cell on an iPhone 8 Plus board and confirmed the BMS handshake completed correctly, the charge IC accepted the cell without fault flags, and the fuel gauge IC initialised at first boot without percentage errors.
- Fuel gauge recalibration after installation: After fitting this cell, disable fast charging and run one full discharge-to-charge cycle at standard rate. The fuel gauge IC calibrates its coulomb counter against the new cell's discharge curve on that first cycle — skipping this step with fast charging active can push current into an uncalibrated cell and produce erratic percentage readings.
Sudden shutdown at 20–30% on the iPhone 8 Plus replacement cell
This is a voltage cliff, not a capacity problem. Under high-draw loads — active LTE modem, screen at full brightness, GPS — the cell voltage drops sharply below the BMS cutoff threshold even when the fuel gauge still shows charge remaining. The fuel gauge IC is reading stored state-of-charge data, not real-time cell voltage under load. One full calibration cycle closes the gap: discharge to automatic shutdown, then charge uninterrupted to 100% at standard rate before resuming normal use.
USB-PD fast charge not accepted on the first cycle after replacement
On the first cycle after a cell swap, the charge IC on the iPhone 8 Plus may refuse to negotiate the USB-PD fast charge contract and fall back to standard 5W charging. This happens because the BMS on the new cell has not yet completed its initialisation handshake with the system charge controller. Plug into a standard 5W Apple charger, let the phone charge fully to 100%, then fast charge works normally on the next cycle. Do not interrupt that first charge session.