What you should be using is the cigarette lighter adaptor, the car was built to connect a battery maintainer that way:
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“Anything really new is invented only in one’s youth. Later, one becomes more experienced, more famous – and more stupid.” - Albert Einstein
I use the clips and run them out between the hood and the windshield for winter storage. My Ktm that doesn't see the same amount of use in the summer and has slightly less easy battery access has the hardwired set.
Just check to make sure cigarette lighter is connected with the ignition off, in some markets (Australia is one) there is no connection when the ignition is off
I have connected mine to the battery direct, just don't forget to disconnect before driving away! Don't ask how I know!