Someone stated "no cooling effect on 12 volt";
well, it should cool on 12 volt!
However, the 12 volt is only in effect while
driving or when engine is running. It shuts off
when the engine stops (unless you have an auxiliary
battery set up to run it).
As noted, get things cold before putting them in
the fridge.
It's also a handy little cooler for keeping frozen
food from thawing when you're on the way home from
the store, but have a long way to go or want to
stop for a while.