Instructables

Are the usb ports on tablets usually wired to supply power?

I have been told that mini and micro ports on tablets are not powered is this true?

meenzal1 year ago
Yes, they follow the USB standard and offer 5 volts. However, the available current is limited and draws from the tablet making it possible to interfere with its operation or even damage it. The USB ports are offered to provide serial connectivity and charging to the tablet, so while you can get power from it, it is not a good idea.
ronarosa (author)  meenzal1 year ago
Hi meenzal,
Thanks for the reply, question is then, what order of current would a USB bluetooth dongle draw? or is it possible to get a USB bluetooth dongle that allows external power supply connection.
Regards, ronchase
For USB 2.0 and 3.0, I believe the max is 500ma but in truth it can vary depending on the device and the circumstances. The dongle itself would define whether or not an external power source can be applied. Many external disk drives have separate power sources, for instance, because the drive motors pull too much current, especially at startup.
verence1 year ago
Depends if they are OTG (On The Go) or even full master ports. If they are not, the tablet is just an external device you can connect to a master device like a PC or laptop.

If they are master or OTG ports, the tablet can be the master device and be connected to stuff like USB flash drives, hard drives, your Bluetooth dongle etc.  In that case they will have to provide power for the external device. A 2.0 USB port can (according to the USB spec.) deliver up to 500mA.
This is true. They are meant to provide power to the tablet as well as a connection to a PC. They are not for trying to connect a thumb drive or power any USB devices from. Tablets have very limited battery life to start with. The manufactured don't want to have anything else sucking power.