Each USB port can provide power to connected devices. This is not always necessary, especially if those devices have their own external power supply. But some devices need the power provided by the USB port to function or reload batteries. A problem with this is that USB ports can only supply a maximum of 500 mA (that’s milliampere) which is usually not a problem if one device is connected to the port.
It could become a problem if a USB hub is connected to the port that is powering multiple devices as it could mean that this exceeds the maximum power that can be supplied by the port. This could result in connection problems and even data loss.
A good start is to find out how much power the USB devices need before connecting them together to an USB hub. The free portable software USBDeview by Nirsoft can do that. Just download the software, unpack it and start it on the target computer system.
Power is one of the information provided by the application. You need to scroll a bit until you find the column as it is located near the end.
You need to click on the Power column title to sort the devices. Not every device requires power and this brings those that do to the top of the list. It is not always that easy to identify devices. The description and drive letter usually help out here. You can also try and disconnect devices and refresh the listing to identify it by looking at which device is missing from the listing after the disconnection.
Did you ever run into troubles running multiple USB devices on one USB port?