BTR6425B Verizon Rezound Compatible Battery 3.7V 1550mAh

Verizon Rezound / ADR6425LVW — 3.7V Li-ion Replacement Battery (BTR6425B)

This is a 3.7V, 1550mAh Li-ion replacement cell for the HTC Rezound on Verizon — model numbers ADR6425 and ADR6425LVW. It matches OEM part numbers BTR6425B, BTR6425, 35H00168-02M, and 35H00168-03M. If the original cell no longer holds adequate charge or the phone shuts down unexpectedly, this cell restores power capacity to factory spec.

• ADR6425 and Rezound 4G LTE fit: Both ADR6425 variants share the same battery bay dimensions, connector pinout, and BMS handshake protocol. The 57 × 44 × 5mm form factor and three-pin connector seat directly into the original tray without modification.
• Bench tested on actual hardware: We ran this cell through a full charge-discharge cycle on the Rezound platform. The BMS accepted the charge IC handshake without error, temperature protection triggered correctly at threshold, and the protection circuit opened as expected at low-voltage cutoff.
• Fuel gauge recalibration on first cycle: On first use after installing this cell, run one complete discharge down to automatic shutdown and then charge uninterrupted to 100% before resuming normal use. This lets the Rezound's fuel gauge IC map the new cell's discharge curve and prevents erratic percentage readings during the first week.

Why the Rezound reports wrong battery percentage after a cell swap

The Rezound uses a coulomb-counter fuel gauge IC that learns the cell's charge and discharge curve over time. When you replace the cell, the IC is still calibrated to the old cell's internal resistance profile and capacity curve — not the new one. Until the IC runs at least one full discharge-charge cycle against the new cell, it will extrapolate percentage from stale data. The mismatch often shows as a sudden jump from 40% to 15% or a reading that stays at 100% well into discharge. One full uninterrupted cycle from automatic shutdown to a complete charge at 3.7V nominal corrects it.

Sudden shutdown at 20–30% on the replacement cell

This happens when the modem radio or display draws a short high-current burst and the cell voltage drops below the BMS protection threshold before the fuel gauge registers the fall. On the Rezound, the LTE radio handoff and screen-on events together can pull enough current to create a voltage cliff on any cell with slightly elevated internal resistance. If this occurs in the first few days after installation, it usually resolves after the fuel gauge IC completes its first full calibration cycle. If it persists beyond two full cycles, check that the battery contacts in the tray are clean and making firm contact — a resistive connection amplifies the voltage sag that triggers BMS cutoff.