Avus A57 Replacement Battery 3.7V 2200mAh Li-ion

Avus A57 — 3.7V Li-ion Replacement Battery (A57/B025)

This is a 3.7V, 2200mAh Li-ion replacement battery for the Avus A57 smartphone. It fits directly in place of part number A57/B025 when the original cell has degraded or failed. Capacity figures are taken from the product specification — 8.14Wh at 3.7V nominal.

• Avus A57 fitment: The A57 uses a single-cell Li-ion pack with a dedicated connector and BMS handshake tied to the phone's charge IC. This replacement cell matches the voltage rail and physical connector so the charge IC accepts it without a fault condition.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the bench. The BMS responded correctly to charge termination, balancing kicked in at full cell voltage, and the protection circuit tripped cleanly on simulated overdischarge.
• Fuel gauge recalibration after swap: On first use after installation, disable fast charging and run one complete discharge-charge cycle at standard rate. This lets the fuel gauge IC build an accurate discharge curve against the new cell before high-current charging is applied to an uncalibrated pack.

Why the A57 reports wrong battery percentage after a cell swap

The A57's fuel gauge IC uses a coulomb counter calibrated against the original cell's discharge curve. When you install a new cell, that stored curve no longer matches reality. The phone reads state-of-charge from a table built for the old cell, so it can show 40% when the cell is actually at 25%. One full discharge to automatic shutdown followed by a full charge at standard rate resets the calibration. After that cycle, percentage readings track correctly against the new cell.

Sudden shutdown at 20–30% on the replacement cell

This happens when the fuel gauge IC hasn't completed its first recalibration cycle. The cell voltage drops sharply under modem or display load — a voltage cliff the old curve didn't predict. The phone's protection threshold triggers before the displayed percentage reaches zero. Run the phone down to automatic shutdown once without interruption, then charge fully to 4.2V to give the coulomb counter a clean reference point.