About this replacement
Logitech UE Ultimate / UE MegaBoom 2 — 3.7V Li-ion Replacement Battery (533-000104)
This is a 3.7V, 2600mAh Li-ion cell replacing part number 533-000104 in Logitech's UE Ultimate, UE MegaBoom 2, UE Kora Boom, and S-00122 portable Bluetooth speakers. It fits the same connector and cell cavity as the original and communicates with the on-board fuel gauge over the same BMS signal line. Swap it when the original no longer holds a usable charge or fails to accept charge at all.
- UE Ultimate and MegaBoom 2 compatibility: Both speakers share the same 3.7V single-cell architecture, the same 533-000104 cell footprint, and the same BMS handshake protocol — that's why one cell covers both platforms. The connector pinout and physical dimensions (66.80 × 21.00 × 18.50 mm) are identical across the listed models.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the UE MegaBoom 2 and confirmed the BMS accepted the new pack without fault codes, the fuel gauge calibrated correctly after one full cycle, and the protection circuit tripped cleanly at the low-voltage threshold before cell damage could occur.
- Monthly discharge practice for UE speaker users: These speakers are often left on a desk and topped off constantly. Run the speaker down below 20% at least once a month before recharging — continuous shallow top-off charging without a full discharge causes fuel gauge drift and accelerates capacity fade on the Li-ion cell.
Audio distorting before the battery indicator reaches empty
At high volume, the amplifier inside the UE Ultimate draws a sharp current spike. As the cell ages and internal resistance rises, that spike causes voltage to sag below what the amplifier needs to run cleanly — producing clipping and distortion well before the battery gauge reads zero. A new cell with lower internal resistance eliminates that sag. After fitting this replacement, run one full charge-to-empty cycle so the fuel gauge re-calibrates to the new cell's actual capacity curve and the indicator tracks correctly.
Speaker won't wake from USB charge after sitting unused for weeks
If the speaker was stored with little charge, the cell can drop below the minimum voltage the USB-C charging circuit needs to initiate a charge session — typically around 2.5V for this cell chemistry. The BMS locks the charge path as a protection measure, and the speaker appears completely dead. Connect it to a 5V USB source and leave it undisturbed for 20–30 minutes — the trickle pre-charge circuit should bring the cell back up to the 3.0V threshold where normal charging resumes. If the cell has been deeply discharged for an extended period, recovery may not be possible and replacement is the correct fix.