Can anyone advise if I need to keep the auxiliary battery hooked up to the car? What is the purpose of it? The voltage is running low on it , am I able to put it on a battery charger, or do I need to replace it.

Thanks ..

 

The auxiliary battery exists to help with the stop/start (aka "Eco") system and serves no other purpose.
It doesn't actually start the car when the stop/start system is in operation, the main/big battery still does that, all it does is power the peripherals (HVAC, lights, Infotainment, wipers etc) for a second or so when the car is restarted after a stop/start initiated shut down.
You can safely disconnect it or remove it entirely and all that will do is permanently disable the stop/start system.
You can put it on a charger or replace it (it is an Exide EK151) if you want, your choice.

 

Thank you for your insight on this, greatly appreciated..

 

The large red cables that are hooked to the auxiliary can they just stay unhooked if i decided to remove the auxiliary, or do i need to hook them up to the big battery? Thank you

 

Just leave them unhooked or remove them altogether, again your choice.
If you leave them (coz it may be difficult to access the other ends) then at least zip tie them up out of the way so they cannot contact any metallic part of the boot/trunk.

 

Are you having any problems?
I ask because my SS system failed after I replaced the very expensive small AUX battery. But I have found I like the car much better without the SS stuff. So if no problems you might consider just leaving it all in place?

Now I do have some SS errors when the car is scanned in SDD but they don't show up anywhere else.

Also the AUX battery is charged by the car so your SS might have already failed if the small battery keeps going dead?
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Problems ..oh were do I begin. (Insert eye roll) Between the battery, car not starting and trying to understand the sdd program help !!

 

Have you read this TSB? It only pertains to the 2013-2015 XF which is what you have?
Maybe you have seen this but it points to your problems for sure.

You mention SDD? Is there anyway you can post the actual codes?
Do you have an operating SDD or trying to set one up?
If so I think your wise even though SDD is a mess to use and learn. At least for me it is.
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What problems are you having? Please give a full description…and is it the stop/start function that is a concern? Why? Unless you are in stop and go traffic regularly, the fuel saving are almost negligible. And the secondary battery for the SS system can be disconnected with no other effect whatsoever.

So can you clarify the problem you are having? A dead battery? These cars like all modern luxury cars require full battery voltage to power the myriad modules. If the battery is not at full voltage all sorts, any sort, of electronic mayhem can result. Battery first! And do not trust a a report of. “the battery is fine”….unless it show a full charge AND passes a load test (simulating the power drain in starting the engine) it is not viable. New batteries are almost NEVER fully charged, so ideally before installing they should be charged.


and you might consider a battery minder as a permanent accessory.