Samsung Galaxy J B605BA Replacement Battery 3.8V 2600mAh

Samsung Galaxy J / SGH-N075T — 3.8V Li-ion Replacement Battery (B605BA)

This is a 3.8V, 2600mAh (9.88Wh) Li-ion replacement battery for the Samsung Galaxy J and SGH-N075T. It fits where OEM part numbers B605BA, B605BK, and B605BU originally shipped. If the original cell has degraded or no longer holds a usable charge, this is the direct swap.

• Galaxy J / SGH-N075T platform fit: Both models share the same 3.8V battery bay, connector pinout, and BMS handshake protocol. One cell covers both — no adapter, no rewiring.
• Bench tested on actual hardware: We ran this cell through a full charge cycle on the SGH-N075T and confirmed the BMS accepted the charge IC handshake without fault codes. The cell held 3.8V nominal under display and modem load with no mid-cycle cutoff.
• First-cycle fuel gauge calibration: On first use after installation, disable fast charging and run one complete discharge down to auto-shutoff, then charge to 100% uninterrupted. This lets the fuel gauge IC map its coulomb counter against the new cell's actual discharge curve before high-current charging loads are applied to an uncalibrated cell.

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

This is a voltage cliff issue, not a capacity problem. When the modem fires during a call or the display peaks in brightness, current draw spikes hard. A new cell with an uncalibrated fuel gauge IC can't map that draw accurately, so the phone sees a voltage dip the OS interprets as empty and shuts down — even though charge remains in the cell. Running one full discharge-to-shutoff cycle, then a full uninterrupted charge, gives the coulomb counter a clean baseline. After that calibration cycle, the reported percentage tracks actual cell voltage accurately under load.

USB fast charge not activating on first cycle after replacement

Samsung's fast charge handshake requires the charge IC to validate the cell's BMS response before it steps up current. On the first cycle with a new cell, the BMS may present a higher internal impedance than the IC expects — so the charger falls back to standard 5V/1A rather than triggering the fast charge protocol. This isn't a faulty battery or a faulty charger. Complete one full standard charge cycle first. On the second cycle, the impedance drops into range and the fast charge protocol activates normally.