Protection circuit and control method for power shortage of car storage battery

The invention discloses a protection circuit of a power shortage of a car storage battery comprising a controller, a voltage sensor and a relay. The voltage sensor is connected with positive and negative electrodes of the car storage battery and a signal output end of the voltage sensor is connected with a signal input end of the controller; a work circuit part of the relay is arranged between the storage battery and a vehicle-mounted electrical appliance and a control circuit part of the relay is connected with the controller. The protection circuit provided by the invention has a lower reformation cost; a BCM (Body Control Module) of the car is utilized as the controller, additional control modules are not additionally arranged, and only one voltage sensor, one relay and corresponding wire bundles are additionally arranged, so that the protection circuit can be widely applied to a plurality of cars.