Apple iPhone 12 A2479 Replacement Battery 3.83V 2815mAh

Apple iPhone 12 / iPhone 12 Pro — 3.83V Li-Polymer Replacement Battery (A2479)

This 3.83V, 2815mAh lithium-polymer cell replaces the original battery in the Apple iPhone 12 and iPhone 12 Pro (OEM part numbers A2479 and A2431). It fits the A2408 board variant as well. Install it when the original cell can no longer hold a usable charge across a normal day of calls, browsing, and background sync.

• iPhone 12 and 12 Pro compatibility: Both models share the same battery connector pinout, BMS handshake protocol, and voltage rail at 3.83V nominal. One cell covers both platforms without modification to the flex cable or connector.
• Bench tested on actual hardware: We ran this cell through a full charge-discharge cycle on an iPhone 12 board. The BMS accepted the handshake without fault codes, the fuel gauge IC initialised correctly, and the charge IC stepped through trickle, CC, and CV phases as expected.
• First-cycle fast charge caution: After installation, disable fast charging for one complete discharge-charge cycle. The fuel gauge IC is calibrated to the old cell's discharge curve. Running USB-PD fast current into an uncalibrated cell before the coulomb counter re-baselines can cause early charge termination or inaccurate percentage readings.

Sudden shutdown at 20–30% on the replacement cell

A new cell in an iPhone 12 can trigger abrupt shutdowns at 20–30% because the fuel gauge IC still references the old cell's internal resistance model. Under high-draw moments — 5G modem activation, screen brightness spikes, or GPS polling — the actual cell voltage drops below what the IC predicts at that state of charge. iOS interprets the voltage cliff as a critically low battery and shuts down the processor before the percentage readout catches up. One full discharge to 1% followed by an uninterrupted charge to 100% forces the coulomb counter to rebuild its resistance model against the new cell.

iPhone 12 reporting wrong battery percentage after a cell swap

The iPhone 12's fuel gauge IC stores a learned discharge curve from the original cell. A new cell with different impedance characteristics means the IC's stored model no longer matches actual cell behaviour, so percentage jumps erratically or reads higher than the real state of charge. This is not a faulty battery — it is a calibration mismatch. Drain the phone to automatic shutdown, charge uninterrupted to 100% with the screen off, and the IC will re-map its curve against the new cell's actual voltage profile.