I'm in the market for a USB hub for my laptop. My main concern is will a non mains powered hub provide necessary power for my external hard and be able to charge my phone.
>will a non mains powered hub provide necessary power for my external hard and be able to charge my phone
Probably not. The hard drive will draw close to the maximum current supplied by a typical USB port. Some laptops have high-current ports, but even then your phone will charge slowly. If you use a USB keyboard and mouse, you could run those from an unpowered hub to free up ports for your high powered devices.
>will a non mains powered hub provide necessary power for my external hard and be able to charge my phone.
My phone warns me if it's charged on a low power USB port that doing so will affect its long-term battery life. I don't understand Li-ion battery tech enough to know if that's true, but if it is then you should probably stick to using your mains charger for your phone. (I know we've got at least one expert here who can correct me if this is wrong).
My experience of cheap USB hubs (having dealt with a bunch at work over the years) is that they are usually nothing but a headache. Especially if you're connecting devices that are drawing power from it and don't have any power supply of their own, you'll get devices disconnecting, USB power warnings from Windows, all sorts of crap. Spend a bit more and get a powered hub, with a mains adapter.
>If you use a USB keyboard and mouse, you could run those from an unpowered hub to free up ports for your high powered devices.
This is good advice, though even then I have 2.5" caddies with drives in them that won't spin up unless they have a second USB plug that's also connected to a powered USB port (see the attached).