About this replacement
Logitech UE Boom 2 — 3.7V Li-ion Replacement Battery (00798-601-8207)
This 3.7V, 2600mAh Li-ion cell replaces the internal battery in the Logitech UE Boom 2 and UE Boom 2 Ultimate portable Bluetooth speakers. It matches the OEM capacity at 9.62Wh and fits the original battery bay without modification. Replace when the speaker no longer holds a useful charge between uses.
- UE Boom 2 and Boom 2 Ultimate compatibility: Both models share the same internal battery bay, connector pinout, and fuel gauge circuit. The BMS on this cell communicates charge state to the speaker's onboard controller the same way the original does — no recalibration required after swap.
- Bench tested on actual hardware: We ran this cell through a full charge and discharge cycle on the UE Boom 2 platform. The BMS held protection thresholds correctly, charge acceptance was normal from the USB port, and the fuel gauge reported accurately across the discharge curve.
- Monthly discharge cycle for UE Boom 2 users: Let the speaker drop below 20% at least once a month before plugging in. Constant top-off charging without ever running the cell down causes fuel gauge drift over time — the speaker will report full charge while actual usable capacity quietly shrinks.
Why the UE Boom 2 shows full charge but audio cuts early
A degraded or shallow-cycled Li-ion cell loses calibration between its real charge state and what the fuel gauge reports. The BMS trips the low-voltage cutoff at the correct cell voltage, but the indicator never warned you it was close. On the UE Boom 2, the amplifier draws a sharp current spike at higher volumes — this accelerates the voltage drop on a weak cell and triggers cutoff faster than the indicator suggests. Replacing the cell and running one full discharge resets the gauge to match the new cell's actual capacity.
Audio distorting before the battery indicator reaches empty
This happens when the cell voltage sags under the combined load of the amplifier and Bluetooth radio before the battery indicator hits its low threshold. The amplifier clips because the supply voltage has dropped below what it needs for clean output — the indicator still shows bars because the fuel gauge tracks average voltage, not instantaneous sag. On the UE Boom 2, this distortion typically starts appearing when cell voltage drops below 3.4V under load. A fresh cell with full capacity eliminates the sag that causes clipping.