12V battery is dead- can not jumpstart

Size of the clamp should not be an issue really unless your not on the right tab. In the fuse box you don't attach the clamp to the bolt. The bolt is there to hold the vertical metal bracket that you clamp too.

 

I like the one where a guy jump started his Prius with a Dewalt 14.4 drill battery. Very safe as it did not deliver alot of current. Built in current limiter. I like that. Limit the inrush which the Prius does not enjoy.

The second you hook up jumpers to a dead 12 volt battery it will take all the current you can deliver. That inrush has to be part of what's damaging so many Prius's. There can't be that many people who screw up a jump. Including so many AAA tow trucks. AAA tow trucks are scary as they have so much jumping current available.

 

These 8 gauge cheapo cables were obviously intended to be used to crank an engine.

For the Prius, you could make an easily-stored set of cables, with just the right size six clips, using 10 gauge or even 12 gauge wire.