Apple iPhone 4G Replacement Battery 3.7V 1300mAh 616-0520

Apple iPhone 4G — 3.7V Li-ion Replacement Battery (616-0520)

This is a 3.7V 1300mAh Li-ion replacement cell for the Apple iPhone 4G, iPhone 4G 16GB, and iPhone 4G 32GB. It matches the original cell dimensions at 115.70 x 63.20 x 15.80mm and connects to the same three-pin flex connector on the logic board. Voltage and capacity figures come from the product data, not estimated values.

• iPhone 4G 16GB and 32GB compatibility: Both storage variants use the same battery bay, connector pinout, and charge IC configuration. The only difference between them is NAND storage — the battery circuit is identical across the lineup, so one cell fits all three models.
• Bench tested on actual hardware: We cycled this cell on an iPhone 4G logic board and confirmed the BMS handshake with the charge IC. The cell accepted charge current without error flags and held voltage through a full discharge sweep without tripping the protection circuit prematurely.
• Fuel gauge recalibration after swap: On first use after installation, run one complete discharge down to automatic shutdown, then charge uninterrupted to 100% before using the phone. This gives the coulomb counter IC a full reference cycle against the new cell's actual discharge curve before iOS begins drawing current under mixed loads.

Why the iPhone 4G reports wrong battery percentage after a cell swap

The fuel gauge IC on the iPhone 4G uses a stored discharge curve from the previous cell to estimate remaining charge. When a new cell goes in, that stored curve no longer matches the actual cell chemistry and impedance. The result is a percentage reading that drifts — often reading 20% when the cell still has significant charge remaining, or jumping unexpectedly. One full discharge-to-shutdown followed by a full uninterrupted charge resets the coulomb counter reference and brings the percentage display back into line.

Sudden shutdown at 20–30% on the replacement cell

This happens when the modem or display pulls a current spike that drops cell voltage below the BMS cutoff threshold — typically around 3.0V — even though the fuel gauge still shows charge remaining. A new cell with an uncalibrated fuel gauge IC makes this worse because iOS cannot anticipate the voltage cliff. The fix is the same calibration cycle: discharge fully to auto-shutdown, then charge to 100% without interruption. After one full cycle, iOS maps the cell's real voltage curve and the premature shutdowns stop.