Samsung SPH-I300 Replacement Battery 3.7V 950mAh BST0359LEB

Samsung SPH-I300 / SCH-I300 — 3.7V Li-ion Replacement Battery (BST0359LEB)

This is a 3.7V, 950mAh Li-ion replacement battery for the Samsung SPH-I300 and SCH-I300 smartphones. It matches the OEM part number BST0359LEB and restores power to devices where the original cell no longer holds a usable charge. Capacity is 950mAh (3.52Wh), identical to the factory specification.

• SPH-I300 and SCH-I300 compatibility: Both models use the same 3.7V single-cell Li-ion pack with the BST0359LEB footprint and connector pinout. The BMS handshake and charge termination voltage are identical across both variants, so one cell fits both without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the SPH-I300 platform. The BMS accepted charge termination at 4.2V and tripped the low-voltage cutoff at the expected threshold without false trips or thermal events.
• Fuel gauge recalibration on first install: After fitting this cell, run one full discharge to automatic shutoff, then charge uninterrupted to 100% before using the phone normally. The SPH-I300 fuel gauge IC calibrates its coulomb counter against that first complete cycle — skipping it causes the percentage display to drift immediately.

Why the SPH-I300 reports wrong battery percentage after a cell swap

The SPH-I300 uses a fuel gauge IC that maps voltage curves from the previously installed cell. When a new cell goes in, the stored discharge curve no longer matches the new cell's actual voltage-to-capacity relationship. The result is percentage readings that read high early and then drop sharply. One complete discharge-to-shutoff followed by a full uninterrupted charge resets the coulomb counter against the new cell's actual curve. After that cycle, percentage reporting stabilises.

Sudden shutdown at 20–30% on the replacement cell

This happens when the cell voltage drops below the modem or display's minimum rail voltage under load, even though the fuel gauge still shows charge remaining. The original cell's internal resistance was known to the BMS; a fresh cell with a different discharge curve can hit a voltage cliff the gauge doesn't anticipate. The fix is the same recalibration cycle — one full discharge to cutoff, then charge to 4.2V without interruption. If shutdowns continue past two full cycles, check that the battery contacts on the phone are clean and making firm contact.