About this replacement
Apple iPhone 8 — 3.82V Li-Polymer Replacement Battery (616-00357)
This is a 3.82V, 1950mAh Li-Polymer cell that replaces the original battery in the Apple iPhone 8. It fits models A1863, MQ6K2LL/A, MQ7H2ZP/A, and related SKUs listed under OEM part numbers 616-00357 and 616-00358. When the original cell degrades past Apple's 80% capacity threshold, iOS throttles CPU performance — swapping the cell restores full clock speed.
- iPhone 8 compatibility: All A1863 and MQ-series iPhone 8 variants use the same 3.82V battery connector, BMS handshake protocol, and fuel gauge IC pairing. One cell fits every regional variant in this lineup.
- Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on an iPhone 8 logic board. The BMS accepted the charge curve without faults, and the fuel gauge IC began tracking state-of-charge correctly after one complete cycle.
- First-cycle fuel gauge reset: After installation, disable fast charging and run one full discharge down to auto-shutdown, then charge uninterrupted to 100%. This gives the coulomb counter a clean baseline against the new cell's discharge curve before high-current charging begins.
Sudden shutdown at 20–30% on a replacement cell
The iPhone 8's fuel gauge IC stores a learned discharge curve from the original cell. A fresh cell has lower internal impedance, so the voltage-versus-capacity curve shifts. When the gauge predicts a voltage cliff using the old curve, it triggers an early shutdown even though charge remains. One full discharge-to-shutdown and uninterrupted recharge resets the coulomb counter and eliminates false cutoffs. After that cycle, reported percentage tracks actual cell state accurately.
USB-PD fast charge not activating after cell swap
On the first cycle after installation, the iPhone 8 charge IC can default to standard 5W charging while it negotiates with the new cell's BMS. This is normal behaviour — the IC runs a conservative handshake on an uncalibrated cell. Complete one standard charge cycle to 100% first. Fast charging via USB-PD typically re-enables automatically from the second cycle onward once the BMS reports a valid state-of-health above 3.6V resting voltage.