I am wondering if I can simply add a power source (for garmin/cell charger) straight off the battery and not have any issues...anyone done this, or Should I go another route? Thanks for your help.

 

If you have a battery tender on your bike it is easy. Just utilize the alligator connectors, cut them off and wire up a cigarette lighter adapter. All you have to do is plug it in. There's lots of youtube videos showing how to do this.