JBL Tune 720 BT Replacement Battery 3.8V 800mAh VDL 702332

JBL Tune 720 BT / Tune 760 BT — 3.8V Li-Polymer Replacement Battery (VDL 702332)

This is a 3.8V, 800mAh lithium-polymer replacement battery for the JBL Tune 720 BT and Tune 760 BT wireless headphones. It replaces OEM part VDL 702332 and restores wireless audio and call functionality when the original cell has degraded. Dimensions are 35.00 × 27.80 × 6.60mm — verify before ordering if your unit has been previously repaired.

• Tune 720 BT and 760 BT compatibility: Both models share the same battery footprint, connector pinout, and BMS handshake protocol. Swapping between them is straightforward because the voltage rail and cell dimensions are identical across the two variants.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on a Tune 720 BT unit. The BMS accepted the pack without fault codes, and the protection circuit tripped correctly at the low-voltage cutoff threshold during deep discharge testing.
• First-charge protocol for accurate talk-time display: Seat the headphones in the charging cable connection and run one complete charge cycle before use. The firmware recalibrates its fuel gauge against the new cell during this cycle — skipping it causes the battery indicator to read inaccurately for the first several sessions.

Why the Tune 720 BT cuts out mid-call on a new battery

The Tune 720 BT draws simultaneously from the audio amplifier and the Bluetooth radio during calls. That combined load produces brief current spikes that can trigger the BMS undervoltage cutoff on a cell that hasn't completed its first full conditioning cycle. The protection circuit reads the voltage sag as a fault and shuts the pack down momentarily. Running two or three full charge-discharge cycles brings the cell to rated capacity and raises the sag floor enough that the BMS no longer trips under normal call load.

Talk time shorter than rated on the first few charges

A freshly manufactured lithium-polymer cell ships at storage voltage — typically around 3.6–3.7V — and has not yet been broken in. On the first charge, the cell does not reach full electrochemical capacity, so available talk time is noticeably shorter than the rated figure. Capacity builds incrementally over three to five full cycles as the electrolyte fully wets the electrode surfaces. After cycle five, measure voltage under load with a multimeter — a healthy cell under light draw should hold above 3.6V.