This is a 2017 XJ-L 3.0L.
For the second time we are getting the "Low Battery" warning and am trying to charge the battery. The first time, a year or two ago, I connected the charger to the battery terminals and it charged up no problem and light off. Now the battery acts like it is getting charged but the light comes on again in a few days. We may just need a new battery, and I guess I will have the dealer do it to avoid having to reset everything. But when searching to educate myself on this issue, I learned I probably should have put the negative charger clamp on the nearby chassis ground.
From new, when I access the battery compartment, I hear a soft beeping sound every few seconds coming from somewhere in there. What makes this sound? In exploring the area, except for the battery, I have a hard time identifying all of the components. Some of the searches I have done, show a second battery for the start/stop. I don't see that here. And what is this loose connector for? Can someone point me to a diagram that will identify these components? Such as, what is the component closest to the rear of the car mounted loosely with rubber bushings?
Thanks.
Bill Z

 

Bill,

I'm pretty sure that the stop-start system in your 2017 XJ does not use the small battery that was ok introduced with the 2013 models. I believe that beginning with the 2016 models the small battery was eliminated and replaced with a capacitor.

Your 2017 XJ is five years old. If that's the original battery, it's probably time for a new one. Your Public Profile shows that you're in the USA but you failed to indicate which state. Climate affects battery life, and extreme heat or cold can cause premature death.

When you attached the negative pigtail of your battery charger directly to the negative battery terminal you may have damaged the Battery Monitoring Module. Battery charging is explained in your Owner's Handbook. If you're going to have your dealer replace your battery, ask them to check that module to make sure it's working properly.

That mystery wire is for the battery transport isolator/protection circuit. It is used when the car is in transit on the ship to the USA. It keeps the car asleep (prevents Convenience Mode from being activated) and protects the battery. Upon arrival, it is disconnected and part of it is discarded.

Stuart

 

Thanks Stuart,
I will have to look again in the manual as I don't recall instructions for charging. I will be aggravated with myself if I didn't follow correct directions.
I will look for that capacitor. Maybe that is it just rearward of the battery.
Any idea where the beeping sound I am hearing is coming from?

 

Beep beep

 

Almost. But a little slower tempo. Haha

 

The beeping is the security system. Puzzled the heck out of me for long time too! It starts whenever anything is opened, and stops after a while. The 2017 has a big capacitor, not a 2nd battery. I read somewhere that for the battery module to detect charging (other than via the alternator), the charger ground must be connected to a ground point on the vehicle, not the -ve pole of the battery. I use the one where that big "AB" ground strap is bolted.

 

Thank you.
Tried charging to the chassis ground as you suggested with the same lack of the battery to accept a further charge.
Probably need a new battery.
Good info on the beeping.

 

Interesting about the beeping?
I have had my 2014 XJR apart for days at a time doing mods and updates and have never heard this beeping? Battery connected and also disconnected.
Can you only hear it around the trunk area? Or inside the passenger compartment?
.
.
.

 

It's a very soft beep. I have only ever heard it outside the car when in the garage and no other ambient noise. Otherwise only when the trunk is open, and never in the passenger compartment.

 

Yes,
I only hear the beeping when the trunk is open and my head is in the trunk messing with the battery.
It is difficult to locate the source even when my head is down in there though. Ha.

 

I have heard the same subtle beeping and also can only ever hear it when the trunk is open. I believe another member (keitheva) mentioned it is the security system?
Cheers
Kevin