The length of time a fridge will run on a car battery depends on several factors, including the type of fridge, the size of the car battery, the temperature setting on the fridge, and the amount of cooling needed.
Portable fridges typically run on AC current, not DC current like a car battery. Therefore, to run a portable fridge on a car battery, you would need a converter that converts the DC current of the car battery to AC current. The converter would need to be powerful enough to handle the cooling unit of the fridge and keep it running continuously.
If you have a small cooler or ice chest, it may run on a car battery for a few hours. However, the length of time it will run depends on the type of cooler and the size of the battery. Generally speaking, small coolers with small compressors can run for about four to six hours on a car battery. Larger coolers with larger compressors may require more power and run for a shorter period of time.
For most portable coolers, you will not be able to run them continuously on a car battery without an inverter. The car battery would quickly drain and the cooling unit may not keep items cool enough. Additionally, running a portable fridge on a car battery could put an extra load on your engine and cause it to run hotter, which could shorten its lifespan.
If you need to keep items cool for an extended period of time while on the road, it is recommended that you use a regular refrigerator or freezer instead of a portable fridge. You can also consider using ice chests and ice packs to keep items cool in addition to a regular refrigerator or freezer.
In conclusion, the length of time a fridge will run on a car battery depends on the type of fridge and cooler you have, the size of the car battery, and the temperature setting on the fridge. 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.