About this replacement
Apple iPhone 13 Pro Max — 3.85V Li-Polymer Replacement Battery (A2653)
This 3.85V, 4300mAh Li-Polymer cell is a direct swap for the original A2653 battery in the iPhone 13 Pro Max and iPhone 13 Pro Max 5G (A2645). It restores power to the processor, display, camera system, and 5G modem after the original cell degrades through repeated charge cycles. Capacity matches the factory spec at 16.56Wh.
- iPhone 13 Pro Max and 13 Pro Max 5G fitment: Both variants share the same battery bay dimensions (90.60 × 67.45 × 4.80mm), connector pinout, and BMS handshake protocol — one cell covers the full model range without modification.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the 13 Pro Max platform. The BMS handshake completed correctly, charge IC accepted the cell without fault flags, and capacity read within spec across three full cycles.
- Fuel gauge recalibration on first use: Disable fast charging for the first complete discharge-charge cycle after installation. This gives the fuel gauge IC time to map the new cell's discharge curve before high-current USB-PD sessions push current into an uncalibrated coulomb counter.
Why the iPhone 13 Pro Max reports wrong battery percentage after a cell swap
The iPhone's fuel gauge IC stores a learned discharge curve from the old cell. When a new cell goes in, that stored curve no longer matches the actual voltage-to-capacity relationship of the replacement. The OS reads state-of-charge from that stale model, so the percentage shown can be ten or more points off. One full discharge to auto-shutdown followed by a complete charge to 100% forces the coulomb counter to resync against the new cell's actual curve.
Sudden shutdown at 20–30% remaining on the replacement cell
This happens when the 5G modem or the ProMotion display triggers a current spike the new cell cannot sustain at that state-of-charge. Voltage drops below the BMS cutoff threshold — typically around 3.0V — and the phone shuts off to protect the cell, even though the fuel gauge still shows charge remaining. It is more common in the first few cycles before the gauge IC recalibrates. Run two full discharge-charge cycles without fast charging and check whether the shutdown threshold rises above 15%.