Apple iPhone 12 Pro Max A2466 Replacement Battery 3.83V 3650mAh

Apple iPhone 12 Pro Max — 3.83V Li-Polymer Replacement Battery (A2466)

This 3.83V, 3650mAh lithium-polymer cell replaces the original A2466 battery in the Apple iPhone 12 Pro Max. It fits the full-size 12 Pro Max only — not the standard 12 Pro or 12. Swap it when your device no longer holds adequate charge through a normal day of use.

• iPhone 12 Pro Max cell fitment: The 12 Pro Max uses a physically larger cell than the 12 Pro — different footprint, different connector orientation. This cell matches that specific chassis cavity at 89.30 × 67.36 × 4.50mm and connects to the same BMS handshake the fuel gauge IC expects.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on an iPhone 12 Pro Max. The BMS accepted the cell without error flags, and the fuel gauge IC initialised correctly after one full discharge-charge cycle.
• Fuel gauge recalibration on first use: After installation, disable fast charging and run one complete discharge down to auto-shutdown, then charge uninterrupted to 100%. This gives the coulomb counter a clean baseline against the new cell's discharge curve before high-current charging begins.

Why the iPhone 12 Pro Max reports wrong battery percentage after a cell swap

The iPhone's fuel gauge IC uses a learned discharge curve built from hundreds of cycles on the original cell. When a new cell goes in, that curve no longer matches actual cell behaviour. The IC reads voltage and estimates state-of-charge from a map that doesn't fit the new chemistry profile. One full discharge-to-shutdown followed by an uninterrupted charge to 100% resets the coulomb counter and rebuilds an accurate curve.

Sudden shutdown at 20–30% after replacement

This happens when the cell voltage drops sharply under load — typically during 5G modem bursts or sustained screen-on use — before the reported percentage hits zero. The fuel gauge IC hasn't yet mapped where the new cell's voltage cliff sits. The phone shuts down to protect the SoC, not because the cell is faulty. Complete two full discharge-charge cycles and confirm the cell rests at approximately 3.83V open-circuit before the third cycle begins.