Samsung SGH-T300 Replacement Battery 3.7V 900mAh Li-ion

Samsung SGH-T300 / SGH-T308 — 3.7V Li-ion Replacement Battery

This is a 3.7V, 900mAh Li-ion cell that fits the Samsung SGH-T300 and SGH-T308 mobile phones. It replaces the original battery when capacity has dropped too far for normal daily use. Rated at 3.33Wh, it matches the voltage and form factor the phone's charge IC expects.

• SGH-T300 and SGH-T308 compatibility: Both models share the same battery bay dimensions and 3.7V single-cell charge circuit, so one cell fits both without modification to contacts or housing.
• Bench tested on actual hardware: We cycled this cell through a full discharge and charge sequence on the SGH-T300 platform. The BMS accepted the charge handshake cleanly and the phone reported stable voltage from the first cycle.
• Fuel gauge recalibration on first install: After fitting this cell, run the phone down to automatic shutdown — do not force power off — then charge uninterrupted to 100%. This gives the phone's fuel gauge IC one clean reference cycle against the new cell's actual discharge curve before you rely on the percentage readout.

Why the SGH-T300 reports wrong battery percentage after a cell swap

The SGH-T300 uses a simple fuel gauge circuit that tracks capacity based on the discharge curve of the cell it was calibrated against — the original factory cell. When you fit a new cell, the stored curve no longer matches the actual voltage-to-capacity relationship of the replacement. The phone may show 40% when the cell is nearly flat, or jump from 60% to 15% without warning. One complete discharge-to-shutdown followed by an uninterrupted full charge corrects this by giving the gauge a fresh reference point to work from.

Sudden shutdown at 20–30% on the replacement cell

This happens when the cell voltage drops below what the phone's processor and RF circuits need under real load — calls, backlight, or keypad — even though the gauge still shows charge remaining. Li-ion cells have a steep voltage drop-off near the bottom of their curve, and an uncalibrated gauge does not track this accurately. The phone cuts out to protect the BMS, not because the cell is faulty. Run one full calibration cycle as described above; if shutdowns continue past 15%, check that the battery contacts are clean and seating flat against the phone's terminals.