Car fridges do not typically work when the car is off because they rely on the car's electrical system for power. The car's electrical system provides the necessary voltage and current to operate the refrigerator and keep it cool.
When the car is off, the electrical system is no longer providing power to the refrigerator, which means it will not be able to keep items cool. Additionally, most car refrigerators use the car's battery for backup power in case the main power source is cut off. Without the car's electrical system, the refrigerator will not have backup power either.
However, some car refrigerators are designed to work on standby mode when the car is off. This standby mode typically allows the refrigerator to keep items cool for a short period of time, usually a few hours at most. The standby mode typically requires a small amount of power to maintain the cool temperature inside the refrigerator.
If you need to use a car refrigerator when the car is off, it is recommended that you connect it to an external power source such as a generator or portable power bank. This external power source will provide the necessary voltage and current to operate the refrigerator and keep items cool.
Car fridges do not typically work when the car is off unless they are designed for standby mode or are connected to an external power source. For maximum safety, reliability, fuel economy, and convenience, it is recommended that you use a regular refrigerator or freezer when you get to your destination instead of trying to run a portable fridge while you're on the road.