About this replacement
T-Mobile Revvl Plus / C3701A — 3.85V Li-Polymer Replacement Battery (CPLD-423)
This is a 3300mAh (12.71Wh) Li-Polymer cell for the T-Mobile Revvl Plus (C3701A) smartphone. It replaces the original CPLD-423 battery when capacity has degraded to the point where the phone no longer holds a usable charge through a standard day. Voltage is 3.85V — matching the original spec exactly.
- Revvl Plus / C3701A fitment: Both model names refer to the same hardware platform. The Revvl Plus and C3701A share the same battery bay dimensions (85.84 × 65.00 × 3.55mm), connector pinout, and charge IC communication — one cell covers both.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the Revvl Plus platform. The BMS handshake completed without error flags, and the charge IC accepted the cell without triggering a fault cutoff.
- Fuel gauge recalibration on first install: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC map the new cell's discharge curve before high-current charging pushes current into an uncalibrated state — preventing erratic percentage readings from the first charge onward.
Sudden shutdown at 20–30% on the Revvl Plus after a cell swap
The Revvl Plus fuel gauge IC stores a charge curve calibrated to the old, degraded cell. When a new cell is installed, the IC still references that old curve and miscalculates remaining capacity. Under modem or screen load, the cell voltage drops faster than the IC predicts, and the phone shuts down before the reported percentage reaches zero. This is a calibration gap — not a defective battery. One full discharge to automatic shutdown, followed by a full charge to 100%, resets the coulomb counter against the new cell's actual curve.
USB fast charge not triggering on the first cycle after replacement
After a cell swap, the Revvl Plus charge IC may default to standard 5V charging on the first cycle rather than negotiating the fast-charge protocol. This happens because the charge IC re-evaluates cell impedance on the first session and applies a conservative current limit until it confirms the cell is healthy. Charge the phone fully once at standard rate without interruption. Fast charge typically re-enables automatically from the second session onward once the IC logs a clean first-cycle result.