About this replacement
Apple iPhone 7 Plus — 3.82V Li-Polymer Replacement Battery (616-00249)
This 3.82V, 3300mAh (12.61Wh) Li-Polymer battery replaces the original cell in the Apple iPhone 7 Plus. It fits models A1661, A1784, and A1785. Use it when the original cell no longer holds charge through a normal day.
- A1661, A1784, A1785 fitment: All three model numbers share the same battery bay dimensions, connector pinout, and BMS handshake protocol. The 3.82V nominal rail matches what the iPhone 7 Plus charge IC expects — swapping between these variants requires no hardware modification.
- Bench tested on actual hardware: We cycled this cell through the iPhone 7 Plus charge IC and confirmed the BMS communicates correctly with the fuel gauge. The protection circuit tripped at the expected low-voltage cutoff, and charge termination occurred at the correct upper threshold.
- Fuel gauge recalibration on first use: 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 charging pushes current into an uncalibrated cell.
Why the iPhone 7 Plus reports wrong battery percentage after a cell swap
The iPhone 7 Plus uses a coulomb counter and a lookup table tied to the old cell's impedance profile. When a new cell goes in, those stored values no longer match the actual discharge curve. The fuel gauge IC reports percentages against stale data until it relearns. One full discharge down to automatic shutdown, followed by an uninterrupted charge to 100%, resets the calibration baseline.
Sudden shutdown at 20–30% on the replacement cell
This happens when the cell voltage drops below the modem or display's minimum rail voltage under load — even though the fuel gauge still shows charge remaining. A fresh cell with an uncalibrated coulomb counter cannot accurately predict that voltage cliff. The phone's power management IC cuts out before the gauge reaches zero. Run one complete discharge-to-shutdown cycle and let the gauge recalibrate — the cutoff point should stabilise above 3.5V per cell on subsequent cycles.