Samsung SGH-A300 Replacement Battery 3.7V 700mAh Li-ion

Samsung SGH-A300 / SGH-K200 — 3.7V Li-ion Replacement Battery

This is a 3.7V, 700mAh Li-ion cell for the Samsung SGH-A300, SGH-A388, SGH-K200, and SCH-302 candybar mobile phones. It fits the original battery bay without modification. Use it when the existing cell no longer holds charge through a standard day of calls and texts.

• SGH-A300 / SGH-K200 compatibility: These models share the same 3.7V single-cell architecture and battery connector pinout. The charge IC in each handset expects the same voltage window — 3.0V cutoff at the low end, 4.2V at full charge — so one cell design covers the full fit list.
• Bench tested on actual hardware: We cycled this cell on the SGH-A300 platform, confirmed the BMS accepted charge without fault flags, and verified the protection circuit tripped correctly at the low-voltage cutoff before the board could draw the cell below 3.0V.
• Fuel gauge recalibration on first install: After fitting this cell, run one complete discharge down to automatic shutdown, then charge uninterrupted to 100%. The phone's fuel gauge IC was calibrated to the original cell's discharge curve — that single full cycle resets it to the new cell and stops erratic percentage readings.

Why the SGH-A300 reports wrong battery percentage after a cell swap

The SGH-A300 uses a fuel gauge IC that tracks charge by measuring voltage against a stored discharge curve from the original cell. A new cell has a slightly different internal resistance and voltage-versus-capacity profile. Until the IC maps one full discharge cycle against the new cell, it interpolates from the old curve and reads inaccurately. One uninterrupted discharge-to-shutdown followed by a full charge corrects this.

Sudden shutdown at 20–30% on the replacement cell

This happens when the cell voltage drops sharply under load — a call or sustained screen use — faster than the fuel gauge IC expects. The phone reads 25% on the display but the cell is already near the 3.0V protection floor, triggering an immediate shutdown. It is a gauge calibration issue, not a faulty cell. Run one full discharge cycle to shutdown and recharge to 100%; the IC recalibrates its curve and the shutdowns stop.