For 12V USB plugs why not add this guy:
12V USB with voltmeter (Amazon). It takes care of two things!
I put something similar in our Axis (actually 3 of them throughout the coach). The one I put in didn't have the voltmeter on it, however--might have to swap one out for this one just because (perhaps I'll swap out the Thor Factory one on the dash with this one which will provide two advantages: I think the one Thor uses only provides 500ma and the voltmeter of course).
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