I bought the Coleman RoadTrip thermoelectric cooler at Walmart for $67 and used it during our weekend at Seqouia. I left it connected overnight with the engine off so the next day, my truck won't start. My hiking buddies just got a regular cooler and used dry ice. Not only does it work well, it's hell of a lot cheaper too! I'm returning the Coleman and probably get the ARB freezer/cooler in the future. But in the meantime, buy dry ice. I'm also replacing my batteries to an Optima Yellow Top.