Ivor, I myself,keep my DT300, in a garage. So, a solar charger would not be a viable option for me,personally. It's really not a big deal, to hook up battery tender pigtails. You will have to remove the seat tub and pick out a good location, to access the plug.
I know BMW, uses 12v port for charging the batteries on some of their models, I have never used one myself.
I just plug in the battery tender jr. and I have never had a problem.
Rich
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