When I bought my 2000 Z3 M Roadster in May the seller threw in his trickle charger. Today for the first time I removed the battery cover and I was pleased to see the former owner had made things very easy for me. He has connectors with a lead wire bolted right to the battery cable clamps so all I have to do is connect the charger cable to the lead wire. But I also noticed that the battery cable clamps seem to be drawn together by a rivet instead of a bolt that one would loosen to remove them, such as when changing a battery. Is that OEM? Do the clamps just slip off when tugged?