This article relates to the USB Port, and Inverter Remote Signal

To prevent the battery against over-discharge this function automatically  switches off the USB output port when Battery 1 voltage is lower than 11.0 VDC. If a compatible inverter is connected and set to remote mode, the controller will also switch off the inverter. This will occur with a delay of 2 to 3 minutes. As soon as Battery 1 reaches a voltage of 12.2 VDC (for LFP) or 12.8 VDC (for SEALED, AGM, or FLOODED) the USB output port is switched on again. If a compatible inverter is connected and in remote mode, it will also be switched on again.