cooler

A cooler most commonly is an insulated box, used to keep food or drink cool. Ice cubes are most commonly put in on top of the items, filling in between them. Ice packs are sometimes used, as they either contain the melting water inside, or have a gel sealed inside that also stays cold longer than plain water.

Coolers are often taken on picnics, and on vacation or holiday. Where summers are hot, they may also be used just for getting cold groceries home from the store, such as keeping ice cream from melting in a hot car. Even without adding ice, this can be a big help, particularly if having to make another brief stop on the way home.

They are usually made from interior and exterior shells of plastic, with a hard foam in between. They also come in sizes from small personal ones to large family ones with wheels. Disposable ones are made only from styrene foam (like a coffee cup) about 2 cm or one inch thick. Most have molded-in handles, a few have shoulder straps.

The cooler was invented in Australia, where it is sometime called an esky, a genericised trademark.

Thermoelectric coolers

Some modern coolers are thermoelectric, plugging in to a car's cigarette lighter socket. Rather than using a compressor and refrigerant like a refrigerator or other heat pump, these use the Peltier effect along with an external fan to draw away the heat. These can also heat the contents instead of cooling them, useful for keeping dinner hot from a drive-through, or even to keep things from freezing in severely cold winter climates.

Thermoelectric coolers typically can drop the temperature by about 40 °F or 22 °C, and can raise it by at least that much. Some better units even have digital thermostat controls. They do draw a significant amount of power however, and can drain a car's battery enough so that it cannot start. Most electric coolers have an undervoltage shutoff at around 10 or 10.5 to prevent this. Many also come with power adapters, which use an electronic transformer to convert alternating current mains or line voltage (100 V to 240 V) down to 12 V, with a lighter-like socket for the cooler's cord to plug in.