Yes you can jump start the car and I have done it. I have a portable jumper lithium pack I keep in the glove box. It came with black and red clamps. So yes, if you have one of these, black is ground and red is positive. You should have also got instructions with the lithium jumper pack.One question though.....if the 12V did die, have any of you jump started the car? I read on how to do it....but wasn't sure if the Portable jumpers (USB ones) were a negative ground system?