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2015 XF Eco/Start Issue

Old 11-07-2017, 10:00 AM
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Default 2015 XF Eco/Start Issue


I have posted this question before but never really received an answer so I am posting again.

I own a 2015 XF 3.0 SC. I am the original owner. The car has approximately 17,000 miles and I only drive around 25 miles each day.

Recently, my Intelligent Eco Start/Stop system has stopped working unless I plug the car into a battery tender overnight. The system will then work as it had for the first two years of ownership for another two weeks and then it starts to work again after putting car on battery tender for overnight. For the first two years of ownership I never needed to use my battery tender but now must plug it in for an overnight charge every two weeks or so.

I get no error messages, codes ,etc. and all features work fine except the Eco Start/Stop system. I suppose that the smaller Start/Stop battery is not holding a charge as long as it had when the car was newer.

I suppose that my question is if there is any harm to vehicle and features other than a non functioning Start/
Stop if I continue to drive it with a low charge smaller Start/Stop battery? I am not in love with this feature and would be fine if it never works. Just wondering if I am causing any harm driving car with a low charged Start/Stop smaller battery. Thank you.
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Paul Fisher (02-02-2019)
Old 11-07-2017, 04:17 PM
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I doubt it is causing any harm.
The secondary battery is not used to start the motor, that is still done by the main battery, the job of the secondary battery is to power the peripherals (lights, infotainment, HVAC etc) once the stop/start system has turned the engine off.
As you have discovered, once the charge in the secondary battery drops below a set level (I'm guessing around 12.2v) the stop/start system is disabled. This is really a safety feature, as you don't want the engine being switched off when the secondary battery is too weak to do it's job properly.
Best solution, which I did on the first day of ownership of my F-Type, is to permanently disable the stop/start system by disconnecting the earth lead from the secondary battery. My car has been running like this for 14 months now without a single problem.
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Paul Fisher (02-02-2019)
Old 11-07-2017, 08:20 PM
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I’m intrigued by the wiring here. Are you connecting the battery tender specifically to the stop start battery? If not, how come the stop start battery is getting charged? If the tender is charging both batteries then doesn’t that mean they are connected together - ie the stop start should be charged from the main battery without the tender? And both would be starting up and running the car? Or have I missed something here?
Just wondering if perhaps your main battery is weak and the tender is addressing that issue?
Old 11-08-2017, 07:53 AM
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Default Stop/Start

Thanks all.


Not sure which battery the tender is attached to and I can't check today since my wife is using the car.

I had read somewhere that when main (large size) battery is not fully charged then I should have erratic electric issues and problems with starting.

My car shows none of these symptoms; no error messages, no codes, no starting problems, no electrical bugs. etc.... It runs 100% fine with the exception of the Eco Start/Stop feature which stops working unless I put the car on the battery tender every two weeks for a quick overnight top off.

Thanks for everyone's input.

Old 11-08-2017, 09:44 AM
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I hate the stop/start feature. Im going to disable it now that I know i can just undo the ground cable
Old 02-02-2019, 04:56 PM
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Default We hate it tooo....

Originally Posted by Akwarr View Post
I hate the stop/start feature. Im going to disable it now that I know i can just undo the ground cable
I sent my bride off for the first time in our newly acquired '15 XF and she was constantly annoyed by the stop start feature...I had forgotten to show her the button to disable it when I set her up in the car.She really dislikes it, as do I so now I know how to bypass it! Many thanks!Other than that we really love the car....Having grown up with Jaguars from 1960 onwards it was like coming home to find a nice one.

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