Samsung Galaxy S8 Active EB-BG892ABA Replacement Battery 3.85V 3900mAh

Samsung Galaxy S8 Active — 3.85V Li-Polymer Replacement Battery (EB-BG892ABA)

This is a 3.85V, 3900mAh Li-Polymer replacement battery for the Samsung Galaxy S8 Active smartphone. It fits SM-G892A and SM-G892U units, including the TD-LTE variant. Capacity is 3900mAh — identical to the OEM specification.

• SM-G892A and SM-G892U compatibility: Both variants share the same battery bay geometry, connector pinout, and BMS handshake protocol. The EB-BG892ABA cell works across all three S8 Active model numbers without modification.
• Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on an SM-G892A unit. The BMS accepted the charge IC handshake on the first cycle, and protection circuits tripped correctly at low-voltage cutoff — no false overcurrent events during testing.
• 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 map the new cell's discharge curve before the coulomb counter locks in its reference points.

Sudden shutdown at 20–30% on the S8 Active after a cell swap

This is a voltage cliff problem, not a capacity problem. A fresh Li-Polymer cell has a slightly different voltage-to-capacity curve than the aged cell the fuel gauge IC was calibrated against. When the modem fires at full power or the screen peaks brightness, the phone pulls a current spike the uncalibrated gauge cannot predict — voltage drops below the safe floor and the BMS cuts power before the reported percentage reaches zero. One full discharge-charge cycle at standard rate resets the coulomb counter against the new curve. After that, shutdowns at 20–30% typically stop.

USB fast charge not activating after battery replacement

The S8 Active's charge IC uses a handshake sequence on the first cycle to verify BMS parameters before enabling Adaptive Fast Charging. On a new cell, that handshake sometimes stalls — the charger falls back to standard 5V/1A and never steps up. To clear it, charge the phone to 100% via a standard charger, then power cycle the device completely. On the next charge session, reconnect the Adaptive Fast Charger — the BMS should complete the handshake and allow the voltage step-up to 9V.