Phonak Compilot Air II Replacement Battery 3.7V 300mAh

Phonak Compilot Air II — 3.7V Li-Polymer Replacement Battery (IP532328)

This 3.7V, 300mAh Li-Polymer cell replaces the original battery in the Phonak Compilot Air II wireless audio streamer. The Compilot Air II streams audio from smartphones, televisions, and other Bluetooth sources directly to compatible Phonak hearing aids. Capacity figures are taken from the product data — 300mAh, 1.11Wh.

• Compilot Air II and 2 Audio Streamer fit: Both units share the same OEM part number IP532328, the same 3.7V cell footprint at 27.50 × 24.60 × 5.00mm, and the same BMS handshake to the charging circuit — a single cell replacement covers both variants.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the Compilot Air II platform and confirmed the BMS completed its handshake correctly, reporting cell state accurately to the device rather than locking at a fixed percentage.
• First-charge protocol for the Compilot Air II: Place the unit in its charging cradle for a complete uninterrupted cycle before pairing it with hearing aids. The streamer needs a full first cycle to let its BMS register the new cell capacity — skipping this causes the charge indicator to read inaccurately from day one.

Base station showing full charge but Compilot Air II cuts off after short use

A replacement cell ships at storage voltage — typically around 3.6V — not at full 4.2V. The base station may register a charge LED as complete before the cell has actually reached capacity, because the BMS has not yet calibrated to the new cell. The streamer then runs out of usable charge faster than expected. One complete, uninterrupted charge cycle in the cradle resolves this. After that cycle, the indicator and actual capacity align.

Compilot Air II cutting out mid-stream under combined Bluetooth and audio load

The Compilot Air II runs a Bluetooth radio and an audio processing stage simultaneously, which draws more current than the cell sees during standby. If the cell voltage sags under that combined draw — common with a degraded original battery — the BMS trips a low-voltage cutoff before the charge indicator reaches zero. A fresh 300mAh cell with intact internal resistance handles the combined draw without triggering cutoff. If drop-outs continue after fitting a new cell, check the device firmware version, as some early Compilot Air II units had power-management bugs patched in updates.