Audio-Technica ATH-AR5BT Replacement Battery 3.7V 700mAh

Audio-Technica ATH-AR5BT — 3.7V Li-Polymer Replacement Battery (KPL603038)

This 3.7V, 700mAh lithium-polymer cell replaces the original KPL603038 battery inside the Audio-Technica ATH-AR5BT wireless headphones. It fits the ATH-AR5BT directly, restoring Bluetooth audio and wireless playback to full capacity. Dimensions are 40.10 × 29.60 × 6.00mm — verify against your existing cell before ordering.

• ATH-AR5BT fitment: The ATH-AR5BT uses a slim Li-Polymer pouch cell with a specific connector orientation and BMS profile matched to the headphone's charging circuit. A mismatched cell voltage or connector pinout will prevent the headphones from powering on — this replacement matches the original on both counts.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the ATH-AR5BT platform. The BMS accepted the new pack without fault codes, and the protection circuit responded correctly to both overvoltage cutoff and low-voltage shutdown thresholds.
• First-charge protocol for the ATH-AR5BT: Charge the headphones to full via USB before the first use. The ATH-AR5BT's onboard circuit needs a complete initial charge cycle to calibrate the battery gauge — skipping this step causes the charge indicator to read inaccurately for the first several uses.

Why the ATH-AR5BT cuts out mid-playback after a battery swap

The ATH-AR5BT draws current from two simultaneous loads: the Bluetooth radio and the audio amplifier stage. Under that combined draw, a new cell sitting near storage voltage — typically around 3.6V — can sag below the BMS cutoff threshold and trigger a shutdown. This is not a fault with the replacement cell. A full charge cycle before first use brings the cell to 4.2V and gives the BMS enough headroom to handle peak draw without tripping.

Charge indicator shows full but headphones cut off after short use

This symptom happens when a replacement cell is installed at storage voltage and the headphone's fuel gauge has not recalibrated to the new cell. The gauge reports 100% based on stale data, but the cell has not completed a full charge cycle. Run one complete charge from flat to full — confirmed by the charge LED extinguishing — then discharge through normal use. After two to three of these full cycles, the gauge reading and actual capacity align reliably. Target a resting voltage of 4.15–4.20V after a completed charge.