About this replacement
Apple iPhone 8 Plus — 3.82V Li-Polymer Replacement Battery (616-00367)
This is a 3.82V, 2690mAh Li-Polymer replacement battery for the Apple iPhone 8 Plus (models A1864, MQ8F2LL/A, and compatible variants). It replaces the original cell when the device shows shortened battery life, unexpected shutdowns, or refuses to hold a charge. Capacity is 2690mAh (10.28Wh), matching the OEM specification under OEM part number 616-00367.
- iPhone 8 Plus model coverage: The A1864, A1897, A1898 variants all share the same battery connector, voltage rail, and BMS handshake protocol. One cell fits all three because Apple did not change the battery interface across regional SKUs of this generation.
- Bench tested on actual hardware: We ran this cell through a full charge-discharge cycle on an iPhone 8 Plus logic board. The BMS completed authentication handshake without error, and the charge IC accepted current at the expected 5V/2A USB-PD rate after the first full cycle.
- First-cycle calibration tip: On first use after installation, disable fast charging and run one complete discharge-to-charge cycle. This gives the fuel gauge IC time to map the new cell's discharge curve before high-current charging pushes current into an uncalibrated coulomb counter.
Why the iPhone 8 Plus reports wrong battery percentage after a cell swap
The iPhone 8 Plus uses a coulomb counter tied to the PMU (power management unit) that retains calibration data from the old cell. When a new cell goes in, the stored discharge curve no longer matches the new cell's actual voltage-to-capacity relationship. The PMU reports percentage based on stale data until it can observe a full discharge and charge cycle on the new cell. After one complete cycle from 100% down to automatic shutdown and back to 100%, the fuel gauge recalibrates and percentage readings stabilise.
Sudden shutdown at 20–30% on the replacement cell
This is a voltage cliff issue, not a capacity problem. Under heavy load — active LTE modem, screen at full brightness, or GPS — the replacement cell's terminal voltage drops sharply before the reported state of charge reaches zero. The PMU reads that voltage drop as a critical threshold breach and cuts power to protect the board. It happens because the fuel gauge IC is still calibrated to the old cell. Run one full discharge cycle to let the PMU learn the new cell's voltage sag profile, and the cutoff point will shift back toward 0%.