About this replacement
Apple iPhone 4S — 3.7V Li-Polymer Replacement Battery (616-0579)
This 3.7V, 1450mAh Li-Polymer cell replaces the original battery in the iPhone 4S across all storage variants — 16GB, 32GB, and 64GB. It matches the OEM dimensions (82.00 × 31.50 × 4.20mm) and connector pinout for the 4S logic board. Swap it when the original cell no longer holds a usable charge or causes unexpected shutdowns.
- iPhone 4S platform fit: All iPhone 4S storage variants share the same battery bay, connector, and BMS handshake protocol. One cell covers every 4S configuration — the logic board does not differentiate by storage tier.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on an iPhone 4S unit. The BMS communicated correctly with the iOS power management IC, and charge termination triggered at the expected 4.2V ceiling without error flags.
- Fuel gauge recalibration after install: After fitting this cell, run one complete discharge down to auto-shutdown, then charge uninterrupted to 100% before normal use. This lets the coulomb counter recalibrate against the new cell's actual discharge curve — skipping this step causes percentage jumps and early shutdown warnings.
Sudden shutdown at 20–30% on the iPhone 4S after a cell swap
The iPhone 4S fuel gauge IC holds a discharge model built from the previous cell's history. When a new cell goes in, that model is stale — the IC predicts voltage behaviour that no longer matches the new cell's curve. Under load spikes from the modem or display, the cell voltage dips below what iOS expects for the reported percentage, and the system shuts down as a protective measure. One full discharge-to-shutdown followed by a complete uninterrupted charge resets the coulomb counter and clears this behaviour.
iPhone 4S reporting wrong battery percentage after replacement
The iOS power management IC uses a stored charge curve from the old cell to estimate remaining capacity. A fresh Li-Polymer cell has a different internal impedance profile, so the reported percentage drifts — sometimes reading 40% and jumping to 15% seconds later. This is a calibration gap, not a fault with the cell. Discharge the phone fully until it powers off on its own, then charge straight to 100% without interruption; the fuel gauge IC rebuilds its model against the new cell and percentage accuracy stabilises.