T-Mobile REVVL V 4G Compatible Battery 3.85V 4000mAh

T-Mobile REVVL V 4G — 3.85V Li-Polymer Replacement Battery (JU001)

This 3.85V Li-Polymer cell replaces the original JU001 battery in the T-Mobile REVVL V 4G and TMRVL4G smartphones. It delivers 4000mAh (15.4Wh) of capacity — matching the factory specification. If your phone shuts down early, charges slowly, or won't hold a charge, this swap restores normal operation.

• REVVL V 4G and TMRVL4G fit: Both model references point to the same hardware platform — same battery bay dimensions (80.00 × 65.30 × 4.60mm), same 3.85V rail, and the same BMS connector pinout. No adapter or modification needed.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on the REVVL V 4G platform. The BMS accepted the cell without error flags, and the charge IC communicated normally with the fuel gauge IC throughout.
• First-cycle calibration on the REVVL V 4G: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC recalibrate against the new cell's discharge curve before high-current charging pushes current into an uncalibrated cell — preventing inaccurate percentage readings from the first day.

Why the REVVL V 4G reports wrong battery percentage after a cell swap

The REVVL V 4G uses a coulomb counter that builds a charge map against the original cell's impedance profile. When you install a new cell, the stored map no longer matches the real discharge curve. The phone reads voltage and estimates state-of-charge from stale data, so the percentage display drifts — often reading 10–15% higher or lower than actual charge. One full discharge to device shutdown, followed by an uninterrupted charge to 100%, forces the fuel gauge IC to write a fresh calibration map against the new cell.

Sudden shutdown at 20–30% on the replacement cell

This happens when the modem or screen draws a current spike the cell can't sustain at that state-of-charge — voltage sags below the BMS cutoff threshold and the phone shuts off instantly. It's not a defective battery; it's the fuel gauge IC cutting power at what it thinks is a safe floor, based on a miscalibrated curve. Run one full discharge-charge cycle without interruption to reset the fuel gauge's voltage-to-capacity mapping. After calibration, the BMS cutoff realigns and shutdowns at 20–30% stop.