That is the way mine works. I have not measuredthe draw though. Never ran down a battery for me so I did not check it.
As soon as I plug the device into the cars OBD port, the power light comes on...(NOT plugged into the USB)
Are they s'pose to do this?? How much current is being drawn?
K, so I shouldn't be concerned...
I plan on adding a little 'solar boost' for extended parkings anyways
Most OBD-II dongles available are powered by the car's diagnostics (DLC) port.
Some, like the Mongoose, are powered by the host computer's USB port. Your ELM device works as it should.