I have two and they have both worked flawlessly multiple times, for jumping weak and/nearly dead batteries as well as providing power to my mobile bar when parked. Both units are Chinese; the actual jump box was about $119, while the shore power unit was about $250. These things can sit idle for months and not lose any capacity at all, so for me they're a no-brainer. I keep the jump box handy and in whichever vehicle I'm using as a DD.
