Apple iPhone SE3 A2819 Replacement Battery 3.88V 2000mAh

Apple iPhone SE 3rd Gen — 3.88V Li-Polymer Replacement Battery (A2819)

This 3.88V, 2000mAh Li-Polymer cell replaces the original battery in the Apple iPhone SE3 (3rd generation), including model A2783. It restores power to the processor, display, cellular modem, and all onboard functions. Swap it when the original cell has degraded through repeated charge cycles and can no longer hold a stable voltage under load.

• iPhone SE3 and A2783 fitment: These models share the same battery bay dimensions, connector pinout, and BMS handshake protocol. The A2819 part number is the correct OEM reference across all SE3 variants — the physical cell and communication interface are identical regardless of carrier or region lock.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on an SE3 unit and monitored BMS communication, charge acceptance, and cutoff behaviour. The protection circuit responded correctly to both trickle-charge entry from deep discharge and full charge termination at 4.35V.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one complete discharge-to-charge cycle at standard rate. This lets the fuel gauge IC map the new cell's discharge curve before high-current charging is applied to an uncalibrated coulomb counter.

Sudden shutdown at 20–30% on the replacement cell

A new cell in an SE3 can trigger abrupt shutdowns in the 20–30% range if the fuel gauge IC is still calibrated to the old cell's voltage-to-capacity curve. The modem and display draw a combined current spike that the coulomb counter misreads as a safe zone until the voltage collapses below the BMS floor. The phone cuts power to protect the cell, even though reported percentage still looks safe. Run one full discharge to auto-off and a full charge at standard rate — the fuel gauge IC will re-anchor its curve to the new cell and shutdowns should stop.

Phone warm near the battery during the first few charging sessions

A fresh Li-Polymer cell has higher internal impedance than a broken-in one, which means the charge IC dissipates more energy as heat during the initial cycles. This is most noticeable during the constant-current phase when the charge IC is pushing current into a cell that hasn't yet conditioned its electrolyte interface. The warmth typically decreases after three to five full cycles as impedance drops. If the device stays hot throughout charging past that point, check that the charge IC is not locked in fast-charge mode — drop to standard 5W input and confirm the case temperature normalises below 40°C.