AudioVox VBT-P1 TDM-2500 Replacement Battery 3.6V 1200mAh

AudioVox TDM-2500 Series — 3.6V Ni-MH Replacement Battery (VBT-P1)

This is a 3.6V, 1200mAh Ni-MH replacement battery for the AudioVox TDM-2500 and TDM-2500XL mobile handsets. It matches the original VBT-P1 specification, including connector and cell chemistry. Swap it in when the original cell no longer holds a usable charge or fails to power the handset.

• TDM-2500 and TDM-2500XL fit: Both models share the same battery bay, connector pinout, and 3.6V Ni-MH chemistry requirement, so one cell covers both handsets without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the TDM-2500 platform. The charge IC accepted the cell on the first cycle, and voltage held steady across a full discharge without premature cutoff.
• Fuel gauge recalibration on first cycle: After fitting this cell, run one complete discharge down to automatic shutoff, then charge to 100% without interruption. The handset's fuel gauge IC was calibrated to the old cell's discharge curve — this single full cycle resets that reference so percentage readings stay accurate.

Why the TDM-2500 reports wrong battery percentage after a cell swap

The TDM-2500 uses a fuel gauge IC that tracks cell capacity by learning the discharge curve of the installed battery over time. When you replace the cell, the IC still references the old curve. This mismatch causes the displayed percentage to read high or jump erratically, especially in the lower half of the charge range. One full discharge-to-shutoff followed by an uninterrupted charge to 100% forces the IC to rebuild its reference against the new cell.

Sudden shutdown at 20–30% on the replacement Ni-MH cell

Ni-MH cells have a steeper voltage drop-off than Li-ion as they approach depletion. Under modem or display load on the TDM-2500, the cell voltage can sag below the handset's cutoff threshold while the fuel gauge still reads 20–30% remaining. This is a calibration lag, not a faulty cell. After two full discharge-charge cycles, the gauge IC catches up to the actual discharge curve and shutdowns at low percentage stop. If the problem persists past three cycles, check that the battery contact pins inside the bay are clean and making firm contact.