AudioVox BTR75 Quickfire Replacement Battery 3.7V 1100mAh

AudioVox Quickfire / GTX75 — 3.7V Li-ion Replacement Battery (BTR75)

This is a 3.7V, 1100mAh Li-ion replacement cell for the AudioVox Quickfire and GTX75 smartphones. It matches the OEM part number BTR75 and fits the original battery compartment without modification. Voltage and capacity are rated at 3.7V / 4.07Wh, identical to the factory specification.

• Quickfire and GTX75 platform fit: Both models share the same battery bay dimensions, connector pinout, and BMS handshake protocol — that is why one cell covers both. The 65.71 × 53.23 × 6.40mm footprint seats flush with the rear cover on either device.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on the Quickfire platform. The BMS accepted the cell without lockout, charge termination fired correctly at 4.2V, and the protection circuit tripped as expected on simulated over-discharge at the low-voltage threshold.
• Fuel gauge recalibration on first use: After swapping this cell in, disable fast charging and run one complete discharge-to-charge cycle at standard rate. The Quickfire's fuel gauge IC was calibrated to the old cell's discharge curve — one full cycle at standard current lets it remap against the new cell before reporting accurate percentages.

Sudden shutdown at 20–30% on the Quickfire after a cell swap

The Quickfire's modem and display pull a combined current spike that the old, degraded cell could no longer sustain — so the phone learned to shut down early to protect it. After installing a fresh cell, the fuel gauge IC still holds that old low-voltage cutoff map. The phone reads 25% state-of-charge, but the IC triggers shutdown before the new cell is anywhere near depleted. One full discharge cycle, letting the phone run down to automatic shutdown and then charging uninterrupted to 100%, forces the coulomb counter to reset its end-point reference against the new cell's actual voltage floor.

Phone feels warm near the battery during the first few charges

A new Li-ion cell has higher internal impedance than a broken-in cell, so the charge IC dissipates more heat during the constant-current phase on cycle one. This is normal and temporary — impedance drops after two or three full cycles as the electrolyte settles. If the device stays warm past the first three charges, check that the rear cover is fully seated, since a raised cover traps heat against the charge IC. Warmth should normalize by cycle four; if it does not, check charge termination with a USB meter to confirm the charger is cutting off at or below 4.2V.