About this replacement
Samsung SGH-E308 / SGH-E330 — 3.7V Li-ion Replacement Battery (BST5068SE)
This is a 3.7V, 750mAh Li-ion replacement battery for the Samsung SGH-E308 and SGH-E330 candybar-style mobile phones. It replaces OEM part numbers BST5068SE, BST2518SE, and BST2948SE. If your original cell no longer holds a charge or the phone shuts down unexpectedly, this cell directly swaps in.
- SGH-E308 and SGH-E330 compatibility: Both models share the same battery bay dimensions, connector pinout, and 3.7V nominal voltage rail. One cell fits both without modification.
- Bench tested on actual hardware: We cycled this cell through a full discharge and charge sequence, confirmed BMS communication with the charge IC, and verified the protection circuit trips correctly at the low-voltage cutoff threshold.
- Fuel gauge recalibration on first use: After fitting this cell, run one complete discharge-charge cycle before enabling any power-saving shortcuts. The phone's fuel gauge IC was calibrated to your old cell's discharge curve. One full cycle lets it map the new cell accurately, so the percentage reading reflects actual capacity.
Why the SGH-E308 reports wrong battery percentage after a cell swap
The SGH-E308 uses a fuel gauge IC that tracks charge state by measuring voltage and current over time against a stored discharge curve. When you install a new cell, that stored curve no longer matches the new cell's actual characteristics. The IC continues reading against old data, so the percentage displayed can be off by 15–25%. One full discharge down to auto-shutdown followed by a complete charge to 4.2V resets the reference point and brings the display back in line.
Phone shuts down suddenly at 20–30% charge remaining
This happens when the cell voltage drops sharply under load — called a voltage cliff — even though the fuel gauge still shows charge remaining. On a degraded original cell, internal resistance rises until the voltage collapses the moment the modem or screen draws peak current. A fresh replacement cell has low internal resistance, so voltage holds steady under that same load. If you see this on the replacement cell, confirm the battery is fully seated and the connector contacts are clean — a poor connection adds resistance and mimics a degraded cell.