Verizon GzOne C731 ROCK Replacement Battery BTR731B 3.7V 1200mAh

Verizon GzOne C731 ROCK — 3.7V Li-ion Replacement Battery (BTR731B / BTR741B)

This 3.7V, 1200mAh Li-ion cell replaces the OEM battery in the Verizon GzOne C731 ROCK rugged mobile phone. It fits directly into the C731 battery bay and restores normal power cycling. Dimensions are 48.45 × 39.38 × 7.96mm — measure your bay before ordering if you're unsure.

• GzOne C731 and C741 compatibility: The BTR731B and BTR741B share the same cell footprint, connector pinout, and BMS handshake protocol across the C731 ROCK platform. Both part numbers fit without modification.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on the C731 platform. The BMS accepted the cell without triggering a fault code, and the charge IC communicated correctly with the phone's power management unit throughout.
• Fuel gauge recalibration on first install: On first use, disable fast charging and run one complete discharge-charge cycle at standard rate. This lets the fuel gauge IC map the new cell's discharge curve before high-current charging pushes current into an uncalibrated cell — preventing erratic percentage readings from the start.

Sudden shutdown at 20–30% on the GzOne C731 ROCK

This happens when the cell voltage drops below the phone's minimum threshold under load — typically during a call, GPS fix, or screen-on activity — even though the fuel gauge still shows remaining charge. A degraded or uncalibrated cell hits a voltage cliff where it cannot sustain the modem's current draw. The BMS trips the cutoff before the gauge catches up. Fix this by running two full discharge-charge cycles at standard rate to let the coulomb counter recalibrate against the new cell's actual voltage curve.

Phone warm near the battery compartment during first charge

A new Li-ion cell has slightly higher internal impedance than a broken-in cell, so the charge IC dissipates more heat during the CC phase on the first few cycles. This is normal and reduces after two to three full cycles as the cell's internal resistance settles. If the phone feels hot rather than warm, or if charging stops before 100%, check that the back cover is seated flush — the GzOne C731's rubber gasket can trap heat if misaligned. Verify charge completion at 4.2V across the battery terminals.