My original post was about parallel adapters and connectors. There were no pictures then. He posted some pictures while I was writing the long post. The original post (no pictures) is the post you quoted in your comment.
Originally Posted by flarssen
Right. If you scroll up a couple of posts there, you can see his parallel adapters.
He does not have Deans on batteries or watt meter. His are all 4mm bullet with the red hoods.
If you have a watt meter that has the correct ends (as he now has since he modified it) or a Y cable, with these plugs, you can plug them in backwards if you don't watch that red goes to red (or if you make the cable with the wrong color, pins, hoods, etc.
If he plugs in a battery to the right hand side of his watt meter now, it will burn out because the voltage polarity will be backwards.
If you have a correctly made Y cable for using parallel batteries, and you plug things in the wrong plug of the Y, you will burn things up with these connectors. That is not possible with other connectors like Deans or XT-60.