What is the capacity of the battery in the dashcam?
Car cameras are primarily designed to be permanently powered. The battery in the camera allows, for example, a delayed shutdown or a parking mode function. When recording, it will last approximately 10-15 minutes without being connected to a power supply.
Cameras that contain a supercapacitor instead of a battery do not hold voltage. They need to be plugged into a power supply for the entire time you want to use them.