EB-BA315ABY Samsung Galaxy A31 Replacement Battery 3.85V 4900mAh

Samsung Galaxy A31 Series — 3.85V Li-Polymer Replacement Battery (EB-BA315ABY)

This is a 3.85V, 4900mAh lithium-polymer replacement battery for the Samsung Galaxy A31. It fits SM-A315, SM-A315F/DS, SM-A310N0, and related variants. Swap it in when the original cell has degraded and the phone no longer holds a useful charge through a normal day.

• SM-A315 variant compatibility: The SM-A315, SM-A315F/DS, and SM-A310N0 all share the same battery bay geometry, connector pinout, and BMS handshake protocol — which is why a single EB-BA315ABY cell covers this entire model cluster without modification.
• Bench tested on actual hardware: We cycled this cell on an SM-A315F/DS unit and confirmed the BMS accepted charge handshake on the first connection, thermal sensors reported correctly to the OS, and charge current stepped down as expected at the 80% threshold.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC map its coulomb counter against the new cell's actual discharge curve before fast-charge current is applied to an uncalibrated cell.

Sudden shutdown at 20–30% on a fresh EB-BA315ABY cell

A new cell with an uncalibrated fuel gauge IC can hit a voltage cliff under heavy load — modem activity, screen-on, or background sync can pull the cell below 3.4V momentarily even while the percentage readout still shows 25%. The phone shuts down to protect the cell, not because capacity is actually low. Run one full discharge to near zero and a full charge without interruption. After that cycle the coulomb counter aligns to the actual cell curve and the shutdowns stop.

USB fast charge not activating on the first cycle after replacement

Samsung's charge IC negotiates fast-charge current only after it reads a known-safe state-of-charge window from the BMS. On a freshly installed cell with no charge history, the BMS may report an ambiguous state that causes the IC to fall back to standard 5W charging for the first session. This is not a fault with the replacement cell or the charger. Plug in, allow the first charge to complete fully at whatever rate the phone accepts, and fast charge will activate normally from the second cycle onward — typically re-engaging at the 15W input level the A31 supports.