For my auto transport business I have a heavy NAPA 12v jumper box, I saw a guy with a 1 lb. "jumper box" the size of a Galaxy cell phone and when he went to jump a HD Ford truck I didn't think it would work...Be as it may I was way wrong, that small box fired it right off !
I bought one with multi charging jacks and it's all that it is cracked up to be for just $48 bucks to your door.