Battery module structure of electrical vehicle

A battery module structure is mounted on an electrical vehicle, including a retention frame mounted to a bar of a chassis of the electrical vehicle. The retention frame includes a top wall connected to the bar by opposite side walls whereby a space is formed between the top wall and the bar for accommodating the battery module. The battery module has a bottom face in which a groove is defined to fit over the bar and a top face on which a peg is formed. A mounting member forming a V-shaped opening is fixed to the top wall of the retention frame for receiving the peg. A lock member is pivoted to one arm of the mounting member and is biased by a spring to have a portion thereof extending into the V-shaped opening to engage and fix the peg of the battery module thereby securing the battery module in the retention frame. The retention frame has a back wall on which three electrodes are mounted. The electrodes are respectively and releasably engageable with jacks of the battery module to supply power to the vehicle. One of the electrodes is a grounding terminal for allowing for direct charging the battery module on the vehicle.