About this replacement
Apple iPhone 13 Pro Max — 3.8V Li-Polymer Replacement Battery (102CS)
This 3.8V, 4700mAh Li-Polymer cell replaces the original battery in the iPhone 13 Pro Max (A3084, A3295, A3296, A3297). It matches the OEM dimensions at 95.00 × 66.00 × 5.50mm and connects to the existing logic board flex cable without modification. Voltage and capacity figures come directly from the product specification, not estimated values.
- iPhone 13 Pro Max platform fit: The A3084, A3295, A3296, and A3297 variants share the same battery bay geometry, flex connector pinout, and BMS handshake protocol — all are regional SKUs of the same 13 Pro Max hardware, so one cell covers the full range.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a 13 Pro Max logic board. The BMS accepted the connection without a fault flag, and the charge IC ramped to full current after the first complete cycle completed.
- Fuel gauge recalibration on first use: After installation, disable fast charging and run one full discharge-to-charge cycle at standard rate. This gives the fuel gauge IC a clean baseline discharge curve against the new cell before high-current charging pushes current into an uncalibrated state.
Why the iPhone 13 Pro Max reports wrong battery percentage after a cell swap
The iPhone uses a coulomb counter and a learned discharge curve stored from the previous cell. When you install a new cell, that stored curve no longer matches the new cell's actual voltage-to-capacity relationship. The fuel gauge IC keeps reading against the old data until it recalibrates. One complete discharge below 10% followed by a full charge to 100% at standard rate resets the curve and brings the percentage display back into alignment.
Sudden shutdown at 20–30% after replacement
This happens when the cell voltage drops sharply under load — modem bursts during a call or cellular handoff pull current the uncalibrated fuel gauge didn't anticipate. The system reads 25% but the cell voltage has already fallen below the safe threshold, triggering an immediate shutdown. It is not a fault with the cell itself — it is the gauge IC firing a cutoff based on stale data. Run two full discharge-charge cycles at standard rate, and the shutdowns will stop once the IC maps the real voltage cliff at the correct state-of-charge point.