AudioVox CDM-9900 Replacement Battery BTR-9900 3.7V 900mAh

AudioVox CDM-9900 / CDM-9950 — 3.7V Li-ion Replacement Battery (BTR-9900)

This is a 3.7V, 900mAh Li-ion replacement battery for the AudioVox CDM-9900 and CDM-9950 candybar-style mobile phones. It matches the OEM part number BTR-9900 and drops into the original battery bay without modification. Voltage and connector position match the original cell exactly.

• CDM-9900 and CDM-9950 compatibility: Both models run the same 3.7V single-cell Li-ion architecture with an identical battery compartment and contact layout. One replacement cell covers both devices without any adapter or wiring change.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on a CDM-9900 unit. The BMS accepted charge current from the phone's onboard charge IC without fault flags, and the protection circuit tripped correctly at the low-voltage cutoff threshold.
• Fuel gauge recalibration on first cycle: After fitting this cell, run one full discharge to near shutdown, then charge uninterrupted to 100% before heavy use. The CDM-9900's fuel gauge IC reads state-of-charge against a stored cell curve — a new cell with a different discharge profile will report inaccurate percentages until that first full cycle resets the reference.

Sudden shutdown at 20–30% on the CDM-9900 after a cell swap

The CDM-9900's fuel gauge IC uses a coulomb counter calibrated to the original cell's discharge curve. A replacement cell with a slightly different internal resistance profile causes the gauge to misread remaining capacity. When the phone's modem transmits — a high-draw event — terminal voltage drops sharply. If the BMS sees the cell voltage dip below its protection threshold, it cuts power immediately, even though the reported percentage still looks safe. One full discharge-charge cycle lets the coulomb counter re-anchor its endpoints to the new cell, which corrects the early-shutdown behaviour.

Phone feels warm near the battery slot during the first charge

A new Li-ion cell typically has higher internal impedance than a broken-in cell. The CDM-9900's charge IC delivers a fixed charge current, so a high-impedance new cell dissipates more energy as heat during the constant-current phase. This is normal for the first one or two charge cycles and reduces as the cell's impedance settles. If the phone remains hot to the touch beyond the second full charge, check that the battery contacts are clean and seated flat — a misaligned cell forces uneven current flow across a smaller contact area, increasing localised heating.