What size are the top post on the battery in a 2015 XKR? Would it be an M8 or an M 10 as I’m looking to hook up a CTEK battery maintainer.

 

I suggest that you attach your CTEK to the remote battery terminals in the trunk using the included alligator clips. That's a lot quicker and easier than attaching it directly to the battery. Note that because your XKR is a 5.0L, you must not attach your negative CTEK pigtail directly to the battery. The factory provided a remote ground post in the floor of the trunk. See your Owner's Handbook.

 

"Note that because your XKR is a 5.0L, you must not attach your negative CTEK pigtail directly to the battery." - Can I ask an explanation for this?

 

You’ll be bypassing the BMS (Battery Monitoring System). See this thread, particularly post #24:
BMS (also in the DYI sticky at the top of this forum)

 

As previously stated,

 

You guys are great. I'll just go hang myself now. **** me for even asking.

 

I don’t think there was any indication of any personal slight. But I am glad you were steered correctly.

Probably 75%?? Of this forum uses the CTEK battery maintainer. FWIW, I don’t on any of my vehicles. And I don’t have any issues with that. Many sit for months, unused.
But the batteries are of good quality and in good serviceable health.