A:Answer I haven't quite figured out how they rate these litium ion jumpers yet, and I'm a mechanic. An older mechanic, but still... Here's what I've done with a jumper very close to this one.
-jump started a 4 cylinder engine where the battery had zero volts. It took a couple tries and it's not recommended but it worked.
-Jump started a v8 engine with a battery that was just a bit too discharged to get it to crank. You can jump start one like this about 4 times without recharging.
They're pretty sweet units. I highly recommend them. Be sure to top off the charge every 3 to 6 months if you don't use it regularly.