Just got a second S1 Pro, plugged into ac wall outlet to charge for a day. With unit still plugged in, I tested speaker thru the Bluetooth connection. Speaker sounded like my first S1, so I figured I don’t need to check channels 1,2. I switched the power switch to off, unplugged iec side of power cord. Switched back on, ran on battery power just fine while streaming Bluetooth. I plugged iec side back in unit, music streamed without a Hiccup.