JBL Tune 750 Replacement Battery 3.7V 700mAh GSP753030

JBL Tune 750 Series — 3.7V Li-Polymer Replacement Battery (GSP753030)

This is a 3.7V, 700mAh Li-Polymer replacement cell for the JBL Tune 750, Tune 750BTNC, and Tune 700BT wireless over-ear headphones. It fits the original GSP753030 footprint at 31.50 × 29.80 × 8.00mm. Replace it when the original cell no longer holds a useful charge after repeated charging cycles.

• Tune 750, 750BTNC, and 700BT compatibility: All three models share the same battery bay dimensions, connector pinout, and BMS handshake protocol — one cell covers the full group.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the Tune 750BTNC. The BMS accepted the pack without error, balanced the cell correctly, and held stable voltage under simultaneous Bluetooth audio and active noise-cancellation draw.
• First-cycle charging on the Tune 750: Charge the headphones fully before the first use. The onboard BMS logs the new cell's capacity baseline on that initial cycle — skip it, and the battery indicator may read inaccurately for the first week of use.

Why the Tune 750BTNC draws harder than a standard Bluetooth headset

The 750BTNC runs two active loads simultaneously — the Bluetooth radio and the active noise-cancellation circuit. That combined draw pulls more current from the 700mAh cell than audio alone would. A degraded original cell struggles under this dual load even when the indicator shows partial charge. A fresh cell at full 3.7V nominal handles both loads without voltage sag triggering an early BMS cutoff.

Headset powers off seconds after leaving the charging cradle

This happens when a replacement cell arrives at storage voltage — typically around 3.0V — rather than at a full charge. The BMS allows the unit to power on briefly, then cuts off when voltage drops under the initial Bluetooth radio startup surge. The fix is straightforward: place the headset back on charge for a complete cycle before use. Once the cell reaches 4.2V and the BMS completes its first full cycle, the cutoff behaviour stops.