Is there a power supply that would power my laptop via USB?

Question

I dont want to buy back up batterys for each individual laptops. I want to know if there is a sort of usb battery that can stay charged and when I need it just plug into my computer via usb to use my laptop? it would be some sort of battery box or something. I have seen something like this before I think but cant remember what it is called.
Thanks

Answer 1

It's called a transformer and cannot plug into a USB port. You should have a plug hole on the laptop for external power source. Most computer shops have a small power supply that converts the power from 240 or 110 whatever to power a laptop. In fact most printers now have built in transformers to reduce power from AC to DC.

Answer 2

The USB ports can supply power to another device, they can't receive power. In other words, your laptop can power something else through USB but something else cannot power your laptop through USB - as far as I know it's one-way deal

Answer 3

I dont think any USB is powerful enough to provide power to a laptop.