Reddit mentions of Jump-N-Carry JNC4000 1100 Peak Amp 12V Jump Starter

www.amazon.com/gp/aw/d/B000JFJLOM

I used one of these for two years doing roadside assistance. The only problems I ever had were starting big ass diesels because two dead batteries just provide too much resistance in the circuit. It even ran a car with no alternator for about 20 minutes and still had power left to be used for jumping for the rest of the night. If it will stand up to professional level abuse, it'll take what you're going to give out. As with all lead acid batteries though, you have to recharge them at least once a month if you want it to be charged when you need it.