Has anybody used these? I bought a set for wife's V70 as they claim to be without polarity and I've read here that Volvos are hypersensitive to use of jumper cables, chargers, etc. In theory, impossible to screw up while jumping another's car. Not used this winter, so I'm still curious (and more than just a little fearful).

They are blue (think Avatar the movie) and the cables meet at some sort of electrical box in the middle which, like a surge protector, has 2 lights that are supposed to turn green if all is well.

Any experiences good or bad? Thanks.