When I connected the modified e-bike controller for the first time a little accident happened. The Anderson SB50 connectors I use for my bike are great since they are polar and you cannot connect the battery in reverse polarity. Of course you have to put the positive and negative terminal in on the right side of the connector housing first. I missed that with the result that i connected the controller in reverse.
Since the MOSFETs conduct from drain to source through the body diode this was practically short circuiting the battery and resulted in a big spark. It was a good thing that I had a 30 A fuse on the battery lead otherwise the connector would probably lock much worse than on the picture above. The controller survived as well, probably thanks to the fuse, otherwise i think $50 worth of MOSFETs would have released the magic smoke.