This used to be a bad idea: alternators put out a lot of spikey noise that would kill $$$ engine electronics, but the battery would act as a huge "capacitor" of sorts and smooth out the power. I don't know if this is still the case, but I'd avoid cranking the engine without the car battery in-circuit.

I'm not sure the 30v is right anyway. Had Blast posted it a day I'd suspect a prank. As it is... there may be 30v somewhere inside this thing but not at the terminals.

What I want to get it is a set of jumper cables with a switch in the middle of the cable, so that I can make the connections and then activate the cable while out of harm's way. If the center switch happened to have a voltmeter, fuse, and enough smarts to not allow a backwards connection then so much the better...