About this replacement
Samsung SCH-U520 Rogue — 3.7V Li-ion Replacement Battery (AB923446GZB)
This 3.7V, 1600mAh Li-ion battery replaces the original cell in the Samsung SCH-U520 Rogue. It fits the 2008-era flip phone directly, using OEM-matched part numbers AB923446GZB, AB463446BA, and AB463446BABSTD. Capacity is rated at 5.92Wh — matching the original specification.
- SCH-U520 Rogue compatibility: The Rogue uses a single-cell 3.7V nominal pack with a three-contact connector carrying voltage, ground, and a thermistor line. This cell matches that pin layout and voltage rail so the charge IC recognises it without fault codes.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the SCH-U520 platform. The BMS accepted charge termination cleanly at 4.2V, and the protection circuit tripped correctly on a simulated short without latching the pack into lockout.
- Fuel gauge recalibration on first install: The SCH-U520 stores discharge curve data tied to the old cell. After fitting this battery, run one full discharge down to auto-shutoff, then charge uninterrupted to 100% before normal use — this resets the coulomb counter against the new cell's actual curve.
Why the SCH-U520 reports wrong battery percentage after a cell swap
The Rogue's fuel gauge IC maps voltage against a stored discharge curve learned from the previous cell. A new cell has a different internal resistance profile, so the same voltage reading maps to the wrong state-of-charge. The gauge can show 40% and shut down moments later, or sit at 100% longer than expected. One complete discharge-to-shutoff followed by a full uninterrupted charge resets the calibration data to match the new cell.
Sudden shutdown at 20–30% on the replacement cell
This happens when the cell voltage drops sharply under load — a voltage cliff — before the reported percentage reaches zero. On the SCH-U520, the modem and display pulling current simultaneously can drag cell voltage below the 3.0V protection threshold faster than the fuel gauge tracks it. The BMS cuts power to protect the cell before the OS can log a low-battery event. Letting the cell complete two to three full cycles tightens the fuel gauge's voltage-to-capacity mapping and pushes that cutoff point lower.