Samsung Stratosphere i405 Replacement Battery EB505165YZ 3.7V 1850mAh

Samsung Stratosphere i405 — 3.7V Li-ion Replacement Battery (EB505165YZ)

This is a 3.7V, 1850mAh Li-ion cell that replaces the original EB505165YZ battery in the Samsung Stratosphere i405 slider smartphone. It fits the SCH-i405, SCH-i405U, and Stratosphere 4G variants. The battery slots into the rear compartment and connects via the original three-contact terminal.

• Stratosphere i405 and SCH-i405U compatibility: These variants share the same battery bay dimensions, connector pitch, and 3.7V nominal voltage rail. The BMS handshake on each model communicates through the same three-pin arrangement, so one cell covers the full range without modification.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on the SCH-i405 platform. The BMS accepted the cell without triggering thermal cutoff or an authentication fault, and charge termination occurred cleanly at 4.2V.
• Fuel gauge recalibration on first use: After installation, run one complete discharge down to automatic shutdown, then charge uninterrupted to 100% before using the phone normally. The Stratosphere's fuel gauge IC maps its coulomb counter to the new cell's discharge curve during this first full cycle — skipping it causes the percentage readout to drift.

Why the Stratosphere i405 reports wrong battery percentage after a cell swap

The i405 uses a fuel gauge IC that builds its charge model from the discharge curve of whichever cell was last fully cycled. When a new cell goes in, the IC still references the old cell's curve — which has different internal resistance and capacity characteristics. The percentage display drifts or stalls because the coulomb counter is feeding data into the wrong model. One complete discharge-to-shutdown cycle followed by an uninterrupted full charge forces the IC to rebuild its reference curve against the new cell. After that single cycle, percentage reporting stabilises.

Sudden shutdown at 20–30% on the replacement cell

This happens when the modem radio or screen backlight draws a current spike that the cell cannot sustain at that state of charge — the terminal voltage collapses below the BMS cutoff threshold momentarily, and the phone shuts down even though the gauge shows charge remaining. It is a voltage-sag symptom, not a capacity fault. A cell that has not been calibrated amplifies the problem because the gauge allows discharge into a voltage range where sag becomes severe. Run the fuel gauge calibration cycle first; if shutdowns continue, check that terminal voltage under load stays above 3.4V using a battery tester before reinstalling.