About this replacement
Samsung SGH-A300 Series — 3.7V Li-ion Replacement Battery
This is a 3.7V 950mAh Li-ion battery for the Samsung SGH-A300, SGH-A388, SGH-K200, and SCH-302. These are early-2000s Samsung mobile phones that share the same battery form factor and voltage rail. If the original cell is swollen, dead, or won't hold a charge, this is the direct replacement.
- SGH-A300 series compatibility: The SGH-A300, SHG-A388, SGH-K200, and SCH-302 all run on the same 3.7V single-cell configuration with a matching connector footprint. The BMS on each of these models communicates over the same three-pin interface, so the charge circuit accepts this cell without modification.
- Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on the SGH-A300 platform. The BMS accepted the cell on first insertion, charge termination triggered correctly at 4.2V, and low-voltage cutoff engaged at the expected threshold without tripping early shutdown.
- Fuel gauge recalibration on first cycle: After installing this cell, let the phone discharge to automatic shutdown before charging back to 100%. The SGH-A300's fuel gauge IC was calibrated to the original cell's discharge curve — skipping this step causes percentage readings to drift or jump erratically until the counter resets.
Why the SGH-A300 reports wrong battery percentage after a cell swap
Samsung's fuel gauge IC on this platform uses a stored discharge curve to estimate remaining capacity. When you replace the cell, that stored curve no longer matches the new cell's actual voltage-to-capacity relationship. The result is percentage readings that jump forward or backward, or a phone that shuts down at 15–20% indicated charge. One full discharge-to-shutdown followed by an uninterrupted charge to 100% forces the coulomb counter to re-anchor its reference points to the new cell.
Sudden shutdown at 20–30% on the replacement cell
This is a voltage cliff issue, not a capacity defect. Under screen-on or active call load, the cell's voltage drops faster than the fuel gauge predicts — the phone's low-voltage protection trips before the displayed percentage reaches zero. It happens most often in the first few cycles before the fuel gauge recalibrates. Run one full discharge cycle without interruption and check resting voltage with a multimeter after shutdown — it should read above 3.0V. If it reads below 3.0V under no load, the cell has reached end-of-life and needs replacement.