Battery-powered USB 3.0 hub?

Is there such thing as a battery powered USB hub? I don’t mean a USB battery pack for charging phones and tablets - those are just power supplies. I mean an actual USB 3.0 hub that is powered by a battery, so I can connect devices (e.g. portable hard drives) that add up to more power than my laptop’s USB port can output, even when I’m away from an AC outlet.