AudioVox BTR-8300 Replacement Battery 3.7V 900mAh Li-ion

AudioVox CDM-8300 / TX30B — 3.7V Li-ion Replacement Battery (BTR-8300)

This is a 3.7V Li-ion replacement battery rated at 900mAh (3.33Wh) for the AudioVox CDM-8300, TX30B, and TX308 mobile phones. It replaces the original BTR-8300 cell, which degrades after repeated charge cycles and can no longer hold a stable voltage under load. If your phone shuts off unexpectedly or won't hold a charge, the original cell is likely the cause.

• CDM-8300, TX30B, and TX308 fitment: These three models share the same battery bay geometry, connector pin-out, and 3.7V nominal voltage rail. The BTR-8300 part number covers all three without any physical modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the CDM-8300 platform. The BMS responded correctly to termination voltage at 4.2V and engaged low-voltage cutoff cleanly without latch faults.
• Fuel gauge recalibration on first use: After installing this cell, run one complete discharge down to automatic shutdown and then charge uninterrupted to 100% before normal use. The phone's fuel gauge IC is calibrated to the old cell's discharge curve — skipping this step causes the percentage readout to drift or report incorrectly from day one.

Why the CDM-8300 reports wrong battery percentage after a cell swap

The CDM-8300 tracks charge state using a fuel gauge IC that builds its model from previous discharge cycles. When you fit a new cell, that stored model no longer matches the actual discharge curve of the replacement. The phone reads voltage and maps it to a percentage based on stale data, so it can show 60% when the cell is actually near depletion. One full discharge-to-shutdown followed by an uninterrupted charge to 4.2V resets the IC's reference baseline against the new cell.

Sudden shutdown at 20–30% on the replacement cell

This happens when the fuel gauge IC has not yet recalibrated and the cell voltage drops sharply under load — typically during a call, when the RF transmitter draws a brief current spike. The cell voltage sags below the BMS cutoff threshold faster than the gauge predicts, triggering an immediate shutdown even though the displayed percentage looks safe. It is not a faulty cell — it is the gauge running on the wrong curve. Complete one full discharge cycle and the shutdowns stop once the IC recalibrates to the new cell's actual voltage-to-capacity relationship.