AudioVox BTR-7126 Compatible Battery 3.7V 800mAh

AudioVox CDM-7126 / CDM-7176 / CDM-8074 — 3.7V Li-ion Replacement Battery (BTR-7126)

This is a 3.7V, 800mAh Li-ion replacement battery for the AudioVox CDM-7126, CDM-7176, and CDM-8074 candybar-style mobile phones. It replaces OEM part number BTR-7126 directly. Capacity is 800mAh (2.96Wh), matching the original cell specification.

• CDM-7126, CDM-7176, CDM-8074 compatibility: These three models share the same battery bay dimensions, connector pinout, and 3.7V nominal voltage rail. A single BTR-7126 cell fits all three without modification to the contacts or housing.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the CDM platform. The BMS held cutoff correctly at low voltage and accepted charge current without tripping at the top of the charge curve.
• Fuel gauge recalibration on first cycle: After installing this cell, run one full discharge to auto-shutoff, then charge uninterrupted to 100% before normal use. The phone's fuel gauge IC is still calibrated to the old cell's discharge curve — one complete cycle resets it against the new cell.

Why the CDM-7126 reports wrong battery percentage after a cell swap

The CDM-7126 uses a fuel gauge IC that learns the cell's discharge curve over time. When you fit a new cell, the IC still references voltage-to-percentage mapping from the old, degraded battery. A fresh Li-ion cell holds a flatter voltage curve at mid-charge than a worn cell does, so the gauge misreads remaining capacity by a wide margin early on. One full discharge-to-shutoff followed by a complete uninterrupted charge resets the coulomb counter and brings percentage reporting back into line. After that first cycle, the gauge tracks accurately.

Sudden shutdown at 20–30% remaining on the new cell

This happens when the cell voltage drops sharply under the load spike from the GSM modem transmitting. Even a new Li-ion cell at 800mAh can dip below the BMS cutoff threshold during a peak transmit burst if the fuel gauge hasn't calibrated yet. The phone cuts power to protect the cell — not because the battery is faulty. Complete the first full discharge-charge cycle to let the gauge recalibrate, then retest. If shutdown still occurs after two full cycles, check that the battery contacts in the bay are clean and making full contact — corroded contacts increase resistance and amplify voltage sag under load. Target resting voltage after a full charge should read 4.1–4.2V at the cell terminals.