Amazing A4c Replacement Battery 3.8V 1500mAh Li3815T43P3h615142

Amazing A4c — 3.8V Li-ion Replacement Battery (Li3815T43P3h615142)

This is a 3.8V, 1500mAh Li-ion battery for the Amazing A4c smartphone. It replaces the original cell when the phone no longer holds charge, powers off unexpectedly, or fails to turn on. Capacity matches the OEM spec at 5.7Wh.

• A4c platform fit: The A4c uses a fixed-connector, non-removable-style slim cell at 3.8V nominal. This replacement matches the original connector pinout and BMS communication protocol, so the charge IC recognises the cell without throwing a fault state.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on A4c hardware. The BMS accepted the cell on first connect, charge termination triggered correctly at 4.35V, and the protection circuit tripped as expected on over-discharge at the low-voltage threshold.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one full discharge-charge cycle at standard current. The fuel gauge IC calibrates its coulomb counter against the new cell's discharge curve — skipping this step is what causes erratic percentage readings in the first few days.

Sudden shutdown at 20–30% on the A4c after a cell swap

This happens because the fuel gauge IC still holds the discharge curve of the old, degraded cell. When the modem fires or the screen brightness spikes, the new cell's actual resting voltage drops sharply under load — but the gauge hasn't learned where the voltage cliff sits yet. The phone reads 25% remaining, hits the real cutoff voltage, and shuts down instantly. One full discharge to 0% followed by an uninterrupted charge to 100% rewrites the coulomb counter baseline and eliminates the premature cutoff.

Phone warm near the battery compartment during the first charge

A new Li-ion cell has higher internal impedance than a worn one. The charge IC on the A4c pushes the same constant-current phase into a cell that hasn't been conditioned yet, and higher impedance means more heat dissipated in the cell itself. This is normal during the first one or two cycles and reduces as the cell breaks in. If the phone feels hot to touch — above roughly 40°C on the back panel — pause charging, let it cool to room temperature, then resume. Heat during subsequent normal charges after break-in points to a charge IC fault, not the cell.