always my pleasure. simply put XB's are hell on batteries. they demand alot of CCA's(cold cranking amps)....the battery should be AGM style.....200 CCA's minimum...and of robust construction. your bike left the factory with a Deka built OEM battery which are outstanding. it is the same battery used by all H-D V-rods from 2008 and up. see link below for my recommendation. Deka.....Big Crank....Super-B....DuraCell.....all from the same factory up the road from me.
and yes....often times when simply turning on the key switch with an existing low battery voltage situation 1 or more relays will buzz. and if 1 or more gets hot to the touch it is a dirty and/or corroded contact/terminal situation which MUST be addressed.
here ya go. best pricing you'll find.
https://www.ebay.com/itm/DEKA-ETX14-...item3d4819a651