JBL Boombox 2 Replacement Battery 7.4V 10400mAh Li-ion

JBL Boombox 2 — 7.4V Li-ion Replacement Battery (SUN-INTE-213)

This 7.4V, 10400mAh Li-ion battery replaces the original pack in the JBL Boombox 2 portable Bluetooth speaker. It fits the Boombox 2 directly and restores cordless audio playback when the factory cell has degraded or failed. Capacity is sourced from the product spec — 76.96Wh total energy storage.

• Boombox 2 fitment: The Boombox 2 uses a single flat Li-ion pack with a proprietary multi-pin connector. The BMS on this replacement communicates with the speaker's charge controller to pass cell voltage reporting and protection handshakes — the same signals the OEM pack sends.
• Bench tested on actual hardware: We cycled this pack through charge and discharge on the Boombox 2 platform. The BMS handled thermal limits correctly, and cell voltage reporting matched expected values at both high-volume amp draw and idle Bluetooth standby.
• Fuel gauge calibration tip for daily Boombox 2 users: If you keep the speaker plugged in most of the time, discharge it below 20% at least once a month before recharging. Constant top-off cycles without a full discharge cause fuel gauge drift on the Li-ion cell, making the charge indicator unreliable over time.

Audio distorting before the battery indicator reaches empty

The Boombox 2 amplifier pulls a sharp current spike at high volume. When the Li-ion cell is aged or degraded, internal resistance rises — even a pack showing 20–30% charge can sag below the amplifier's stable operating voltage under load. The speaker clips the audio signal before the protection circuit trips, so you hear distortion well before any low-battery warning. A fresh cell with lower internal resistance keeps the voltage rail stable under the same load spike, pushing clean output until the true cutoff threshold.

Speaker won't charge after sitting unused for several months

Li-ion cells self-discharge at roughly 2–3% per month. A Boombox 2 stored for six months or more can drop the cell below the USB-C Power Delivery minimum acceptance voltage — typically around 2.5V per cell. At that point the charger handshake fails and the speaker shows no charge activity at all. Connect the speaker and leave it on charge for 30–45 minutes without interruption; the BMS on this replacement pack includes a recovery trickle-charge mode that brings the cell back up to the USB-C acceptance threshold before switching to normal CC/CV charging.