T-Mobile Galaxy S3 Replacement Battery 3.7V 1400mAh

T-Mobile Galaxy S3 / Galaxy SIII — 3.7V Li-ion Replacement Battery

This is a 3.7V, 1400mAh Li-ion battery for the Samsung Galaxy S3 and Galaxy SIII, sold under the T-Mobile network variant. It fits the Galaxy S3, Galaxy SIII, Galaxy S 3, and Galaxy S III model designations. Install it when the original cell no longer holds a useful charge or fails to power the device through a normal day.

• Galaxy S3 variant coverage: The S3 shipped across multiple carriers with near-identical battery bays and connector pinouts. All listed model names refer to the same physical handset generation, so this cell fits each variant without modification.
• Bench tested on actual hardware: We cycled this battery through charge and discharge on Galaxy S3 hardware. The BMS accepted a full charge cycle without cutoff errors, and cell voltage held stable across light CPU and screen loads.
• Fuel gauge recalibration after swap: On first use, run one complete discharge down to automatic shutdown, then charge uninterrupted to 100% before using the phone normally. This lets the fuel gauge IC map its readings against the new cell's actual discharge curve rather than the old one.

Why the Galaxy S3 reports wrong battery percentage after a cell swap

The Galaxy S3 uses a coulomb-counter-based fuel gauge IC that builds its percentage model from accumulated charge and discharge data on the previous cell. When you fit a new cell, that stored model no longer matches the new cell's actual voltage-to-capacity curve. The result is percentage readings that drift, jump, or plateau well above zero before the phone shuts down. One full uninterrupted discharge-charge cycle forces the IC to re-learn the curve and brings percentage accuracy back in line.

Sudden shutdown at 20–30% remaining on a replacement cell

This is a voltage cliff issue, not a capacity problem. Under high instantaneous load — mobile data handshake, screen at full brightness, GPS active simultaneously — the cell voltage drops sharply below the BMS cutoff threshold even though the reported percentage still looks healthy. The Galaxy S3's modem and display together can pull enough current to cause this on a fresh cell if the fuel gauge IC hasn't completed one calibration cycle yet. Run that first full cycle, and if shutdowns persist past 15%, check that the battery contacts on the device are clean and making full contact with the cell terminals.