What can cause a sudden shut dow

I have a backfire hammer (regular not sledge), and I was skating at a car meet, when all of the sudden, 5-6 miles into my ride, I hear a "click" and my motors stopped working and the board shut down, I wasn't able to turn the board back on that night but 2 days later I tried again and it works perfectly fine. It was on 70% battery at the time so It started me quite a bit. Has anyone else had this problem with an electeic skateboard, if so what could it be?