JBL Tuner XL Replacement Battery 3.7V 3350mAh Li-ion

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

This is a 3.7V, 3350mAh (12.4Wh) Li-ion replacement battery for the JBL Tuner XL portable speaker. It fits directly where the original cell sits inside the Tuner XL housing. Use it when the original pack no longer holds charge or the speaker shuts off unexpectedly during playback.

• Tuner XL cell match: The Tuner XL runs a single-cell 3.7V Li-ion configuration. The BMS inside the speaker expects a cell in that voltage window — feeding it anything outside that range trips the protection circuit and halts charging. This cell stays within spec throughout its charge cycle.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the Tuner XL platform. The onboard BMS accepted the cell cleanly, balanced the charge curve correctly, and the protection circuit did not trip during high-volume playback draws.
• Monthly discharge cycle for the Tuner XL: This speaker spends most of its life plugged in or topped off between short sessions. Let the battery drop below 20% at least once a month before recharging — constant shallow top-off charging without a full discharge causes fuel gauge drift on the Tuner XL and accelerates capacity fade on the cell.

Capacity fade from constant desk-top charging on the Tuner XL

The Tuner XL is frequently left on a desk or charging dock between uses, rarely discharged below 50%. Li-ion cells cycled only in the upper charge band — repeatedly between 80% and 100% — accumulate stress on the cathode faster than cells that see full cycles. Over several months, the fuel gauge reads full but actual usable capacity drops noticeably. Replacing the cell resets the clock, but the pattern repeats unless charging habits change.

Audio distorting before the battery indicator reaches empty

As a Li-ion cell ages, its internal resistance rises. Under the amplifier's current draw — especially at higher volumes — the cell voltage sags below the level the amplifier needs to operate cleanly, even when the indicator still shows remaining charge. The result is audible distortion or clipping before the speaker shuts off. Fitting a fresh cell with lower internal resistance eliminates the sag and restores clean output. If distortion returns within a few months on the new cell, check that the speaker is not being run at maximum volume continuously, as that sustains the highest current draw on the cell.