Galaxy Stratosphere II 4G Replacement Battery 3.7V 1800mAh

T-Mobile Galaxy Stratosphere II 4G — 3.7V Li-ion Replacement Battery

This is a 3.7V, 1800mAh Li-ion replacement battery for the T-Mobile Galaxy Stratosphere II 4G smartphone and its variants (Galaxy Stratosphere II, Galaxy Stratosphere 2). It slots into the original battery bay and connects to the device's charge IC via the standard contact array. Capacity is 1800mAh — matching the original specification from the factory.

• Galaxy Stratosphere II family fit: The Stratosphere II, Stratosphere II 4G, and Stratosphere 2 all share the same battery bay dimensions and contact pinout. Voltage rail is 3.7V nominal across all variants, so one cell covers the full model range without any adapter or modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on a Galaxy Stratosphere II 4G unit. The charge IC accepted the new cell without fault flags, and the BMS held voltage within spec through the full discharge curve.
• Fuel gauge recalibration on first cycle: After installing this cell, run one complete discharge-charge cycle before relying on the percentage readout. The fuel gauge IC on the Stratosphere II was calibrated against the discharge curve of the original aged cell — a full cycle lets it remap against the new cell's actual characteristics.

Sudden shutdown at 20–30% on the Galaxy Stratosphere II

This is a voltage cliff problem, not a capacity problem. When the Stratosphere II's modem fires up for a 4G LTE handoff or the screen brightness peaks, current draw spikes hard. A degraded or uncalibrated cell cannot hold voltage under that load and collapses below the BMS cutoff threshold — even though the fuel gauge still shows 20–30% remaining. Replacing the cell removes the voltage sag, but the percentage readout will still be wrong until the fuel gauge IC runs one full calibration cycle. After that cycle, shutdown and percentage should align.

Phone not powering on after the battery sat discharged in a drawer

Li-ion cells discharged below roughly 2.5V trip a BMS lockout — the protection circuit blocks current flow to prevent damage from charging a deeply depleted cell at full rate. The Stratosphere II's charge IC may show no response at all when you first plug in. Connect the phone to a wall charger (not a PC USB port, which limits current) and leave it untouched for 20–30 minutes — the charge IC uses a trickle pre-charge mode to bring the cell up to 3.0V before resuming normal charge. If the screen shows a low-battery animation and then progresses, the BMS has cleared the lockout.