Samsung X750 3.7V Replacement Battery 600mAh Li-ion

Samsung X750 / X650 — 3.7V Li-ion Replacement Battery

This is a 3.7V, 600mAh (2.22Wh) Li-ion cell for the Samsung X750 and X650 mobile phones. Both handsets share the same battery bay dimensions and voltage rail, so one cell covers either model. Capacity is taken directly from product specification — not estimated from third-party sources.

• X750 and X650 shared battery platform: Both models run the same 3.7V single-cell architecture with a matching connector pin-out and BMS handshake. Swapping between the two devices requires no modification — the protection circuit communicates the same way on either handset.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the X750 platform. The onboard BMS accepted the cell without fault codes, and the protection circuit engaged correctly at low-voltage cutoff.
• First-cycle fuel gauge reset: After fitting this cell, run one full discharge down to automatic shutdown, then charge uninterrupted to 100% before using fast charging. The fuel gauge IC on these handsets calibrates its coulomb counter against the first complete cycle — skipping this step leaves the percentage reading offset against the new cell's actual discharge curve.

Why the X750 reports wrong battery percentage after a cell swap

The X750 uses a fuel gauge IC that tracks charge state by counting coulombs against a stored discharge curve from the original cell. A new cell has a different internal resistance and capacity profile, so the stored curve no longer matches reality. Until the IC runs one full discharge-to-shutdown and uninterrupted recharge cycle, the reported percentage will be offset — sometimes by 15–20%. After that single calibration cycle, the gauge reads against the new cell's actual curve and stabilises.

Sudden shutdown at 20–30% on the replacement cell

This happens when the fuel gauge IC has not yet recalibrated and the phone's displayed percentage does not reflect the cell's true state of charge. Under modem transmission or screen-on load, the cell voltage drops sharply near depletion — the BMS cuts power to protect the cell before the OS registers 0%. The fix is the same calibration cycle: discharge fully to automatic shutdown, then charge to 100% in one uninterrupted session. After that cycle, the OS percentage and the actual cell voltage threshold align, and the early shutdowns stop.