JBL Tuner 2 Compatible Battery 3.7V 3350mAh IAA004NA

JBL Tuner 2 — 3.7V Li-ion Replacement Battery (IAA004NA)

This is a 3.7V, 3350mAh (12.4Wh) Li-ion replacement battery for the JBL Tuner 2 portable Bluetooth speaker. It replaces OEM part IAA004NA and restores power to the speaker's wireless audio and FM radio functions. Fit the correct part before ordering — the Tuner 2 uses a different cell than the original JBL Tuner.

• Tuner 2 fitment: The Tuner 2 runs its amplifier, Bluetooth radio, and FM tuner off a single 3.7V cell. JBL uses a BMS that communicates charge state to the onboard fuel gauge — the replacement carries the same cell configuration and connector orientation to maintain that handshake.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the Tuner 2 platform and confirmed the BMS accepted charge without triggering a protection cutoff. The fuel gauge reported state-of-charge accurately across the discharge curve.
• Fuel gauge reset after installation: After fitting a new cell, run the speaker down past the low-battery warning tone before recharging fully. The Tuner 2's fuel gauge recalibrates its empty and full thresholds on the first complete cycle — skipping this leaves the indicator reading 10–15% short of actual capacity.

Capacity fade from constant top-off charging on the Tuner 2

The Tuner 2 is often left on a desk, plugged in whenever it drops below 80%. Li-ion cells stressed by constant high-state-of-charge cycling lose capacity faster than cells that see a fuller discharge range. The cell spends most of its time above 4.0V, which accelerates cathode degradation. Discharge to below 20% at least once a month before recharging to slow this process.

Audio distorting before the battery indicator reaches empty

At high volume, the amplifier draws a current spike that the aged cell can't sustain without voltage sag. When cell voltage dips under load, the amp clips the audio signal before the fuel gauge registers a low state-of-charge. The speaker sounds like it's overdriven, but the indicator may still show two bars. A fresh 3350mAh cell holds voltage under that load — if distortion persists on a new battery, lower volume to rule out the amplifier itself.