First post here. Just bought 2015 XFR. 16k miles. Shop said aux battery at 24%. Does car system monitor battery life? Shop also said getting the aux battery can be difficult. Any idea where I can get one in Austin, TX?

 

Are you sure you even have an auxiliary battery?
AFAIK the XF switched from two batteries (main + auxiliary / stop/start) to a single battery in 2013, so a 2015 XFR should have only one battery.
Check in the boot/trunk under the cover and see what you can see.

 

 

I stand corrected!
If it really is a 2015 XFR that is.
Anyway, the stock Jag stop start battery is an Exide EK151 which shouldn't be too hard to find, see this thread on the UK XF forum: https://www.jaginfo.org/showthread.p...+start+battery

Edit - just a thought - why not permanently disable the stop/start system and save yourself buying a new battery?
I disabled the stop/start system on my F-Type the first day I got it home, I found the system to be incredibly annoying and pointless and completely unsuited to a car like the F-Type. I simply disconnected the earth lead which runs off the negative terminal to a bolt on the floor of the trunk. You could do the same on your car, or better still completely remove the stop/start battery, it won't effect anything else. The only reason I haven't removed the stop/start battery on the F-Type is because it is tucked under the rear hatch panel and there is no way of getting at the mounting bolts without ripping out the rear of the hatch.