About this replacement
Samsung SGH-i620 / SGH-i640 Series — 3.7V Li-ion Replacement Battery (AB414757BE)
This is a 3.7V, 1600mAh Li-ion replacement battery for the Samsung SGH-i620, SGH-i640, and SGH-i640v slider smartphones. It replaces OEM parts AB414757BE and AB514757BE. Capacity is drawn from product specifications — 5.92Wh total energy.
- SGH-i620, i640, i640v compatibility: All three models share the same battery bay dimensions, connector pinout, and BMS handshake protocol. The 60.35 × 49.81 × 5.24mm cell seats flush in each chassis without modification.
- Bench tested on actual hardware: We cycled this battery through charge and discharge on the SGH-i640 platform. The BMS accepted the charge IC handshake on first connection, with no fault flags thrown during the initial full charge cycle.
- Fuel gauge recalibration on first use: After fitting this battery, disable any fast-charge mode and run one complete discharge-to-charge cycle before normal use. The SGH-i620's fuel gauge IC needs a full cycle against the new cell's discharge curve before it can report accurate percentages — skipping this step causes the OS to mirror the old cell's calibration data onto the new cell.
Why the SGH-i620 shuts down suddenly at 20–30% battery remaining
The SGH-i620 uses a coulomb-counter fuel gauge that maps voltage against a stored discharge curve. When the installed cell is new, the stored curve belongs to the old, degraded cell — so the voltage cliff appears earlier on the display than it does in reality. Under load spikes from the modem or display backlight, the cell voltage briefly drops below the BMS cutoff threshold even though the percentage shown looks safe. The phone interprets this as a hard undervoltage event and cuts power immediately. One full calibration cycle — discharge to auto-off, then charge uninterrupted to 100% — re-anchors the fuel gauge to the new cell's actual voltage profile.
Phone will not power on after the battery sat in storage for months
Li-ion cells self-discharge during storage. If the cell drops below approximately 2.5V, the BMS enters a lockout state to prevent damage and will refuse a standard charge current. The SGH-i620's charge IC will not push recovery current into a locked-out cell at normal charge voltage — the phone simply shows nothing when connected. Connect the phone to a charger and leave it for 20–30 minutes without attempting to power it on; the trickle pre-charge circuit slowly brings the cell back above the BMS recovery threshold of around 2.8–3.0V, at which point normal charging resumes.