JBL Tuner XL Replacement Battery 3.7V 2600mAh Li-ion

JBL Tuner XL — 3.7V Li-ion Replacement Battery (SUN-INTE-220)

This is a 3.7V, 2600mAh (9.62Wh) Li-ion replacement battery for the JBL Tuner XL portable Bluetooth speaker. It fits directly into the Tuner XL and restores power to both the audio amplifier and the Bluetooth radio. Replace this cell when the original no longer holds a usable charge through a normal listening session.

• Tuner XL power rail: The Tuner XL runs a single 3.7V Li-ion cell that feeds both the Class D amplifier and the Bluetooth radio through shared power management. Any replacement cell must match that voltage and hold steady current delivery across the full discharge curve — voltage sag under combined amp and radio draw is what kills audio performance before the battery indicator reads empty.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the Tuner XL, monitoring BMS cutoff behaviour at both the high-draw end (loud playback) and the low-draw end (idle Bluetooth). The BMS handshake completed cleanly and no false low-battery shutoffs occurred during discharge.
• Monthly full-discharge cycle: If the Tuner XL sits on a desk and gets topped off constantly without ever fully discharging, the fuel gauge drifts and the cell accumulates shallow-cycle degradation. Let it discharge below 20% at least once a month before recharging to keep the fuel gauge calibrated and slow capacity fade.

Audio distorting before the battery indicator reaches empty

This happens when the cell's internal resistance has risen enough that the amplifier's current draw pulls terminal voltage below the point where clean audio is possible — even though the indicator still shows charge remaining. The Class D amp in the Tuner XL clips when supply voltage sags under load, producing distortion before a low-battery cutoff ever triggers. A worn cell with elevated internal resistance hits this sag point earlier in the discharge curve. A new cell at full 3.7V nominal holds the voltage rail steady and pushes that distortion threshold back toward the actual end of discharge.

USB charging not waking a deeply discharged Tuner XL

If the Tuner XL sits unused for weeks, the cell can drop below the USB-C PD minimum acceptance voltage — typically around 2.5V — and the charger will not negotiate a charge session because the BMS blocks input to protect the cell. The fix is a slow pre-charge: use a low-output USB charger (5V/0.5A) rather than a fast charger, leave it connected for 20–30 minutes, and let the BMS trickle the cell back above the acceptance threshold. Once the cell recovers to approximately 3.0V, normal charging resumes.