Samsung BST5118S Galaxy D357 Replacement Battery 3.7V 1000mAh

Samsung SGH-D357 — 3.7V Li-ion Replacement Battery (BST5118S)

The BST5118S is a 3.7V, 1000mAh Li-ion cell that fits the Samsung SGH-D357 candybar handset. This battery slots directly into the D357 battery bay, restoring power to the phone when the original cell no longer holds voltage under load. Voltage and capacity match the OEM spec: 3.7V nominal, 3.7Wh total energy.

• SGH-D357 compatibility: The D357 uses a single-cell Li-ion pack with a three-contact connector — positive, negative, and BSI (Battery Status Indicator) pin. The BST5118S carries the correct BSI resistor value so the phone's charge IC recognises the pack and does not lock out charging.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the D357 platform. The charge IC accepted the pack on the first insertion, reached full charge termination without tripping into fault mode, and the BMS held the low-voltage cutoff at the correct floor.
• Fuel gauge recalibration on first use: After fitting this cell, run the phone down to automatic shutdown and charge back to 100% without interruption. The D357's fuel gauge IC calibrates its coulomb counter against that first full cycle — skipping it causes the percentage display to drift against the actual cell state.

Why the SGH-D357 reports wrong battery percentage after a cell swap

The D357 uses a fuel gauge IC that stores a discharge curve from the previous cell. When a new cell goes in, that stored curve no longer matches the actual voltage-to-capacity relationship of the fresh cell. The gauge reads voltage but maps it to the old cell's profile, so it can show 40% when the cell is near empty — or 20% when there is still usable charge remaining. One full uninterrupted discharge-to-shutdown followed by a full charge resets the coulomb counter and re-anchors the gauge to the new cell's curve. After that cycle, percentage readings stabilise.

Sudden shutdown at 20–30% on the replacement cell

This is a voltage cliff failure, not a capacity failure. Under screen-on or network-search load, the cell's internal resistance causes a sharp voltage drop that crosses the low-voltage cutoff threshold before the percentage display reaches zero. The phone shuts off to protect the cell, even though the gauge still shows charge remaining. The fix is to complete that first full calibration cycle — once the gauge IC maps the real discharge curve of the new cell, it adjusts the shutdown trigger point accordingly. If shutdowns persist after two full cycles, check that the battery contacts are clean and making firm connection at all three terminals.