For hybrid vehicles, the metal protective lid of the DC-DC converter does not have sufficient strength, and therefore, when the back of the rear seat is pressed by the weight of a passenger, the lid may distort and interfere with the insulation rubber cap of the electrical terminal. If this problem is left unattended, the cap may be damaged, and in the worst case, the terminal and the lid may short-circuit, in which case the main fuse could break, and the engine could stop and fail to restart.