People, the SP2pro is a tablet with a STANDARD USB-2 port!
USB 2 ports provide 5vdc at 0.5 Amps
USB 3 ports provide 5vdc at 0.9 Amps.
Volts x Amps = Watts - do the Math.
It amazes me that people think it's a USB port, this is a USB cable and that's a USB drive, just plug them inn an it must work. All give yourselves a forehead slap.
Use a powered USB-hub and plug stuff into that and NEVER have problems. Some powered hubs even have higher than 0.5A and 0.9A output, like 2.1A for charging devices or running demanding peripherals like drives. Just because it is rated at 2.1A does not mean it is going to try and stuff 2.1A into a device needing only 0.5A. It just means that if the device needs 2.1A it can get it. It will suck *just* what it needs, not take all that is available, well, not unless there is a short circuit.
Now, to testing with a laptop means squat!! Laptop makers have all sorts of rules they make up themselves for USB output behavior. Not unusual to have a laptop with three USB ports, two with 0.5A and the other with 2.1A for charging. Along with that they will often have a CMOS option to enable, limit or disable the the power totally or even above 0.5A depending on the battery and/or charging status at the time.
Why create problems where there should be none. Use a powered USB hub with at least one port designated as "charging" and you will NEVER have a issue. Now, do not start on the portability of dragging along a hub. If you think that way, then let me sign you up with some free Cloud providers.