Sprint BA S390 Smartphone Replacement Battery 3.7V 2800mAh

Sprint BA S390 — 3.7V Li-ion Replacement Battery (BA S390)

This is a 3.7V, 2800mAh Li-ion cell that replaces the original BA S390 battery in compatible Sprint smartphones. It also cross-references OEM part numbers RHOD160, 35H00123-00M, and 35H00123-02M. If your original cell no longer holds a charge or fails to power the device, this is a direct swap at matching voltage and capacity.

• Cross-reference coverage: The BA S390, RHOD160, 35H00123-00M, and 35H00123-02M part numbers share the same voltage rail and physical connector. One replacement cell covers all four part numbers without any modification to the battery bay or contacts.
• Bench tested on actual hardware: We ran this cell through full charge and load cycles, verifying BMS cutoff thresholds and charge acceptance at 3.7V nominal. The protection circuit responded correctly to overcharge and over-discharge limits throughout testing.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging for one complete discharge-charge cycle. This gives the fuel gauge IC time to map the new cell's discharge curve before high-current charging pushes current into an uncalibrated cell — preventing erratic percentage readings from the first charge onward.

Sudden shutdown at 20–30% on the replacement cell

This happens because the fuel gauge IC is still using the discharge curve from the old, degraded cell. When the screen or modem draws a spike of current, the new cell's voltage drops sharply in a region the gauge hasn't mapped yet. The phone interprets that voltage dip as a dead battery and shuts down, even though capacity remains. One full discharge-to-cutoff followed by a complete charge cycle forces the coulomb counter to recalibrate against the actual cell curve and eliminates most of these premature shutdowns.

Phone reports wrong battery percentage after cell swap

The fuel gauge IC stores a learned model of the old cell's impedance and discharge profile. A new cell has different internal resistance, so the stored model produces inaccurate state-of-charge readings — the percentage displayed can jump, stall, or read high while the device is already in low-voltage territory. Drain the battery fully until the phone shuts itself off, then charge uninterrupted to 100% without removing the cable. After one complete cycle, the gauge IC updates its reference curve and percentage accuracy stabilises.