About this replacement
Logitech UE MegaBoom — 7.4V Li-ion Replacement Battery (533-000116)
This 7.4V 3400mAh Li-ion battery replaces the original pack in the Logitech UE MegaBoom portable Bluetooth speaker (S-00147). It fits both OEM part numbers 533-000116 and 533-000138. Capacity is rated at 25.16Wh, matching the original cell spec.
- UE MegaBoom and S-00147 compatibility: Both the UE MegaBoom and S-00147 variants share the same battery bay dimensions, connector pinout, and BMS handshake protocol — this pack covers both without modification.
- Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on a UE MegaBoom unit. The BMS accepted the pack without error flags, and the fuel gauge tracked state-of-charge accurately across the full discharge curve.
- Monthly discharge cycle — UE MegaBoom specific: The MegaBoom's always-on Bluetooth standby drains the cell slowly even when not playing audio. Let the pack drop below 20% at least once a month before recharging — constant top-off charging without a full discharge causes fuel gauge drift on this model and accelerates capacity fade.
Why the UE MegaBoom shows full charge but audio cuts out after an hour
The fuel gauge IC in the MegaBoom calibrates its charge estimate against the battery's internal resistance. When the original cell ages, resistance rises and the gauge loses accuracy — it reports 100% based on a baseline that no longer matches the actual cell capacity. The result is a full-charge indicator that collapses within an hour of real audio draw. Replacing the cell resets the baseline, but the gauge needs one full discharge-to-shutdown and recharge cycle to recalibrate to the new pack.
Audio distorting at high volume before the battery indicator reaches empty
At high volume, the MegaBoom's amplifier pulls a sharp current spike that causes momentary voltage sag on a degraded or deeply discharged pack. The amplifier clips under that sag, producing audible distortion before the battery LED has signalled low charge. This is a voltage delivery problem, not an audio hardware fault. A fresh cell with lower internal resistance holds the voltage rail stable under amplifier load — charge the new pack fully before the first high-volume session to confirm the distortion clears.