Samsung Galaxy A21s EB-BA217ABY Replacement Battery 3.85V 4900mAh

Samsung Galaxy A21s 2020 — 3.85V Li-Polymer Replacement Battery (EB-BA217ABY)

This is a 3.85V, 4900mAh Li-Polymer replacement battery for the Samsung Galaxy A21s 2020, covering SM-A217F, SM-A217F/DSN, and SM-A217F/DS variants. It matches OEM part numbers EB-BA217ABY and GH82-22989A. Fit this cell when the original no longer holds a charge or shuts down unexpectedly under load.

• SM-A217F variant coverage: The SM-A217F, SM-A217F/DSN, and SM-A217F/DS all run the same 3.85V battery rail, share the same connector pinout, and use the same BMS handshake — one cell fits all listed variants without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the SM-A217F platform and confirmed the BMS accepted the cell, charge termination triggered correctly at full capacity, and no protection trip occurred during standard load draws.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one full discharge-charge cycle at standard rate. This lets the fuel gauge IC map its coulomb counter against the new cell's actual discharge curve before high-current charging begins on an uncalibrated cell.

Sudden shutdown at 20–30% on the Galaxy A21s after a cell swap

The Galaxy A21s uses a coulomb-counter fuel gauge that was calibrated to the old cell's discharge curve. When a new cell goes in, the gauge still references the old curve, and it misjudges the voltage cliff — the point where cell voltage drops sharply under modem or screen load. The phone reads 25% but the actual open-circuit voltage is already near the BMS low-voltage cutoff. One full slow discharge cycle from 100% to auto-shutdown, followed by a full charge, forces the fuel gauge IC to re-anchor its reference points to the new cell.

USB fast charge not activating on the first cycle after replacement

Samsung's Adaptive Fast Charging handshake requires the BMS to confirm cell state before the charge IC ramps up current. On a freshly installed cell with no cycle history, the BMS may reject the elevated current request and default to standard 5V/1A charging on the first session. This is not a fault in the adapter or the cable. Charge the phone fully at standard rate once, then unplug and replug — the BMS will have logged one complete cycle and will accept the fast charge protocol on subsequent sessions.