About this replacement
Apple iPhone 11 — 3.83V Li-Polymer Replacement Battery (616-00641)
This 3.83V, 3500mAh lithium-polymer battery is a direct cell replacement for the Apple iPhone 11, covering model variants A2111 and A2221. It restores power to the display, processor, cellular radio, and all running applications. Fit the original battery when capacity has dropped or the cell no longer holds a charge through a normal day.
- A2111 and A2221 compatibility: Both variants run the same power architecture — identical voltage rail at 3.83V nominal, same connector, and the same BMS handshake protocol with the iPhone 11 charge IC. One cell fits both without modification.
- Bench tested on actual hardware: We cycled this cell on an iPhone 11 board and confirmed the BMS completed a full charge handshake, the charge IC accepted current without fault codes, and the fuel gauge IC tracked state-of-charge across a complete discharge curve.
- Fuel gauge recalibration after install: On first use after fitting, disable fast charging and run one full discharge-to-charge cycle at standard 5W. This lets the coulomb counter recalibrate against the new cell's discharge curve before high-current charging pushes into an uncalibrated fuel gauge.
Sudden shutdown at 20–30% on the replacement cell
A new cell sometimes has a steeper voltage cliff than the aged cell the fuel gauge IC was calibrated against. Under high-current loads — 5G modem, screen at full brightness, background sync — the cell voltage drops faster than the gauge predicts. The iPhone interprets this as a valid low-voltage cutoff and shuts down, even though the percentage shown was 25%. One full discharge-recharge cycle at standard rate allows the coulomb counter to remap its estimate to the new cell's actual curve. After that cycle, shutdowns at 20–30% typically stop.
USB-PD fast charge not triggering on the first cycle after replacement
After a cell swap, the charge IC on some iPhone 11 units defaults to standard 5W on the first charge session while it verifies the new cell's internal resistance and BMS response. This is normal behaviour — it is not a fault with the battery or the charger. Disconnect the cable, power the phone off completely, then reconnect to an 18W USB-PD adapter. Most units accept the fast-charge handshake on the second connection attempt. If it still reverts to 5W, complete one full standard-rate cycle first, then retry the 18W adapter.