The cools up to 40 degrees below ambient temperature is the key. I don't know enough about the mechanism inside to see how it would react to getting wet from additional ice. Reviews indicate it is not particularly well insulated. See the reviews
http://www.amazon.com/Koolatron-P20-Com ... B00009PGNS We have a Waeco refrigerator and on our month long trip our problem was keeping things from freezing. It worked beautifully with no fear of it getting too hot. This would have been a concern because its residence was in the back of our Subaru Outback wagon and when we stopped the interior would get well over 100 degrees. One of the things we discovered was that frozen "bag meals" were very handy when traveling. Pull into a camp site and ten minutes later dinner is ready, OK there was some set up time.