The invention is a protection method for vehicle-mounted
computer hardware and battery, the vehicle-mounted device of the method comprises a
power unit, a
control unit, a function unit, a hard disc and a
voltage testing device. The ACC or ON output
voltage of an igniting switch is monitored by a make-break testing unit, as the basis of stopping hardware operation and shutdown or standby of the vehicle-mounted device. The protection method comprises the steps that: 1) the ACC or ON output
voltage of the igniting switch is tested by the make-break testing unit; 2) a automobile operation state is judged according to the high state or low state of the ACC or ON output voltage of the igniting switch; 3) when the automobile igniting switch switches from ON or ACC position to OFF close position, the testing voltage of the make-break testing unit changes from
high voltage to
low voltage, then the hard disc operation is stopped immediately, the instruction hard disc magnetic head is repositioned, the vehicle-mounted device is in shutdown or standby state. By timely control, stopping of hard disc operation previous to power off is realized, preventing hard disc damage and
data loss caused by power off and preventing battery exhaustion of vehicle-mounted device caused by long-term operation when the automobile is in stall state.