Yup...lots of posts on battery tenders but i didn't see any that really addressed how people installed them "semi permanently" .

Taking a page out of my 928 install i did the same on the XK. Only difference being the 928 has a jump post cover under the hood at the front of the car (battery in the back)

2013 XKRS
Simple enough.
Disconnect the battery first.
Found the jump post in the rear fender, found a suitable attachment for a ground (continuity with the Neg battery lead was good) and luck would have it there was a grommet back there also that lead to the out side of the car near the driver side exhaust tip area.

I found and old battery tender lead with the clips on it and modified it with some connectors(you can order a similar ready made lead on Amazon), made a simple bracket and through trial an error found a reasonable enough spot to mount it out of sight. The bracket is just wedged in between the rear lower fender and the lower valance. Seems secure enough. It sits on the drivers side and i have to walk over the cable to get in the car and even if i do drive off with it plugged in , it will simply disconnect.

Pictures are worth a 1000 words...

.



GREEN= ground location
BLUE= grommet that give access to outside.
Red= jump post and positive terminal
WHITE= in line fuse close to the 12V source.

 

There’s a couple of solutions in this thread;
https://www.jaguarforums.com/forum/x...5/#post1421456
Both use covered sockets, one for a DC lighter socket to plug in the external maintainer. The other uses a covered AC socket to power the maintainer carried in the car.