A 12V fridge will eventually drain any battery, including car batteries. It’s important to understand how much energy the portable 12-volt fridge uses, which mostly depends on what model you buy, what the ambient temperature is, and what setting you put the 12V fridge to. Many have built-in battery voltage monitors, but they can still drain your battery. Most of the best camping fridges use about 1 amp hour each hour on average and car batteries can have around 50 amp hours total. But you don’t want to run your battery down too low, so you should either run your vehicle or connect another power source like a portable power station, solar panels, or generator.