Samsung Galaxy M51 Replacement Battery EB-BM415ABY 3.85V 6800mAh

Samsung Galaxy M51 / SM-M515 — 3.85V Li-Polymer Replacement Battery (EB-BM415ABY)

This is a 3.85V, 6800mAh (26.18Wh) Li-Polymer replacement battery for the Samsung Galaxy M51 (SM-M515, SM-M515F/DSN). It slots into the same position as the original EB-BM415ABY cell and reconnects to the same flex connector on the board. If your M51 drains fast, shuts down unexpectedly, or won't hold a charge, this cell replaces the degraded original.

• SM-M515 variant coverage: The SM-M515F/DSN and standard SM-M515 share the same battery bay dimensions, flex connector pinout, and BMS communication protocol — one cell fits both without modification.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on an SM-M515F board. The BMS handshake completed correctly, charge IC accepted the cell without fault flags, and voltage held stable under display-on load.
• 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 the new cell's discharge curve before Samsung's Adaptive Fast Charging pushes high current into an uncalibrated cell — preventing early percentage errors.

Why the M51 reports wrong battery percentage after a cell swap

The Galaxy M51 uses a coulomb counter inside the fuel gauge IC that was calibrated to the original cell's charge curve over hundreds of cycles. When you install a fresh 6800mAh cell, that stored curve no longer matches what the new cell actually does. The IC keeps using the old data, so it reports inaccurate percentages — sometimes jumping 10–15% in either direction. One full uninterrupted discharge down to automatic shutdown, followed by a complete charge to 100%, forces the IC to rewrite its reference curve against the new cell.

Sudden shutdown at 20–30% after replacement

This is a voltage cliff issue, not a capacity problem. Under high-current load — 5G modem bursts, screen at full brightness, or GPS active — the cell voltage drops sharply for a fraction of a second. If it dips below the BMS's undervoltage threshold, the protection circuit cuts output instantly, even though the reported percentage still shows 20–30%. On a new cell this usually means the fuel gauge IC hasn't finished recalibrating. Run one full discharge-charge cycle with fast charging off first. If shutdowns continue after two full cycles, check that the flex connector is fully seated — a partially connected cell shows elevated internal resistance and exaggerates voltage sag under load.