Has yet to fail to start anything including my 6.6 Duramax diesel. The reviews that says it won’t start a completely dead battery didn’t read the instructions, you can jump a car without a battery if you want too. The auto feature don’t come on if the battery is below a certain point but the instructions clearly tell you what to do for those asking there is a small button on the unit that disables the “security” feature. I do it all the time starting my lawnmower without a battery that I have yet to purchase one for. As long as your sure what your trying to start is hooked up correctly pos and negative correct and not touching then your good to go.
UPDATE*** I bought this last July 2018 it worked fine I kept in inside my house stored well charged once a month and used it very few times it looks brand new. I got it out to use the other day and lights flash then goes off. I contacted the manufacturer who told me it was a couple months out of warranty so I have to pay 45% of the msrp for them to refurb it on their site which is almost 400$ for the gb150 i paid 299$ here on amazon which is barely more than to get mine fixed. i paid 100 bucks for a stanley 5 years ago and it works perfect still. if you pay 3 to 500 dollars for a jump box it SHOULD have a better warranty. They dont stand behind their products do yourself a favor and find a different brand. There are several for less or about the same that has a terrific warranty. According to the email i was sent even kf it would have happened within the year there are many stipulations which would still result in then not fixing it or charging the 45% msrp to repair so they know its junk!! This is the first 1 star ive ever given on any product and many reviews i dont take it lightly but i hope to save someone else from getting ripped off like i did! lesson learned no more overseas junk unless they have a great warranty.