Check with the "Battery Tender" website, as they have just released a new item about as big as your thumb that plugs into your battery tender outlet from your battery that has a USB plug-in at the end. You can then get a short extension from the standard USB to the micro plug in for your phone. With this device, you would not have to hard wire anything in your trunk!! Mine works great and I carry it in my tour pack.
They also have a similar device that you can plug-in to your battery tender lead and it has an LED screen (about 1/4" by 1") that tells you the voltage of your battery. It also has three lights - i.e. green/yellow/red that alerts you of the condition of your battery. Both items are rather in expensive as well.
Hope this helps!
Ride Safe!!
Roger
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