About this replacement
JBL Boombox 2 — 7.4V Li-ion Replacement Battery (SUN-INTE-213)
This 7.4V, 13500mAh (99.9Wh) Li-ion battery replaces the original pack in the JBL Boombox 2 portable Bluetooth speaker. It restores the speaker's ability to run off battery rather than staying tethered to mains power. Dimensions are 135.00 x 75.00 x 22.20mm — verify your original pack before fitting.
- Boombox 2 platform fit: The Boombox 2 uses a single large-format Li-ion cell pack at 7.4V nominal. The BMS monitors cell voltage and communicates charge state to the speaker's onboard fuel gauge — the replacement pack uses the same connector pinout and BMS handshake protocol as OEM.
- Bench tested on actual hardware: We cycled this pack through charge and discharge on the Boombox 2 platform. The BMS engaged cell balancing correctly across both cells, and the speaker's charge indicators tracked accurately through the full voltage range without false-full readings.
- Fuel gauge calibration tip: Let the battery discharge below 20% at least once a month before recharging. The Boombox 2 is often kept topped off between uses — constant partial charging without a full discharge cycle causes the onboard fuel gauge to drift, making the charge indicator unreliable over time.
Bluetooth dropping at high volume on the Boombox 2
At maximum volume, the Boombox 2's Class D amplifier pulls a sharp current spike that combines with the Bluetooth radio draw. If the battery's internal resistance has risen — either through age or a new pack that hasn't been conditioned — the combined load causes a brief voltage sag. The BMS interprets this sag as a low-cell event and throttles output, which the radio registers as a power interruption. Run two full charge-discharge cycles on the new pack before testing at high volume; internal resistance drops as the cells condition.
Speaker won't wake from USB-C charge after sitting discharged
If the Boombox 2 sits unused for several weeks in a discharged state, the cell voltage can drop below the USB-C Power Delivery minimum acceptance threshold — typically around 2.5V per cell. At that point the charger handshake fails and the speaker appears completely dead. Connect the USB-C cable and leave it for 20–30 minutes without expecting any indicator light — the BMS needs trickle current to bring the cell voltage back above the PD acceptance floor before normal charging begins. If the indicator still doesn't respond after 40 minutes, check that the USB-C source delivers at least 5V/2A.