Well i just purchased a 2015 xf portfolio and im trying to find out what you guys do to stop the eco mode .I no i can hit the button to turn it off,but went on search to find out if you guys remove the ground cable on the small battery

 

Yep, that's exactly what I did on my F-Type which has the same two battery system. It was the very first thing I did the day I got it home some 3.8 years ago now.
I simply unbolted the end of the earth cable (which runs off the negative terminal of the small/secondary battery) from where it bolts to the floor of the boot, and zip tied it up out of the way so it couldn't contact any metal part of the car.
Hey presto, completely and totally and permanently disabled SS system with zero effect on anything else and has never given me a single problem.
Then, about two months ago I completely removed the secondary battery from the car, and no change at all.

 

There is a long thread on this question, about 4? months ago. You access an electrical panel on the right inside wall of your trunk, boot, and you unplug a really hard to reach plug that is the power supply for the eco engine kill feature. My hand is too big, I gave up.
There was no mention of the secondary battery. I don't even know if my xf has one, or where.
P.

 

2016 was the changeover year when Jags went from the two battery SS system to one battery.
So you have only one battery and yes the way to permanently disable SS one a one battery car is to find and pull the correct plug.

 

Thanks guys ill go out and disconnect it , im sure it help give the alternator a longer life

 

where i circled is that were you disconnect

 

Sure looks like it!
The set-up on the F-Type is different, it has a nut going onto a bolt by itself with no black battery bracket involved.
Just double check that the other end of that cable is going to the negative terminal of the secondary battery and nothing else.

 

do you have a pic of yours

 

Sorry, no pics of mine.
But there are some pics of others' F-Types battery systems floating around somewhere on the F-Type sub-forum, I looked for quite a while but couldn't find what you want.
There is also a thread/post of someone with a 2015 X250 who did the same cable disconnection and it worked, but they get a "warning" on the dash every time they start the car, I suspect the same will happen to you.
Anyway, even without pics, that nut/bolt you have circled is 100% sure to be the correct one, rip it off and find out!
Just undo the screw/bolt holding the cable to the slot in the bracket and slip it off then zip tie it up.

 

ill give it a try

 

well i disconnected it and voila (eco) stop and start is removed , drove around town for an hour and no ill effects

unscrewed 8mm bolt on left and disconnected cable



and put back screw



Then taped with electrical tape and zipped tied





results