The trick there is knowing what to look for, as there's no standard way to indicate this feature. This almost always works - but a grossly obsolete Dell running Windows XP (don't ask) failed to charge an iPad mini and only started the flow of electricity to an Android phone after taking a minute or so to recognize that device as a form of external storage. Instead, you have a few basic rules of USB charging that often get bent or broken - thanks to the different flavors of USB connectors shipped since the Universal Serial Bus's debut in the late '90s.įirst, any laptop that's awake should charge any device plugged into it, even if the computer isn't plugged into the wall. If only charging one mobile device from another had the same boring predictability of plugging a charger into a wall outlet. Is there an easy way to figure out if a USB port can charge a phone when the laptop is asleep or even powered off?Ī.