I am with SOV211 on this. Yes, your car has two batteries, one for the ECO start and I do not know how they are connected to the charging system, but I have never found that car places really understand batteries and how they perform. They are always going to see adequate voltage when they pull the car into the work bay because the car just ran and the alternator voltage tickled the battery voltage up. The question is what is the battery voltage after it has been at rest for a while? They are not going to just let your car sit in the work bay for a couple of hours and then test it. I also have never trusted those load checkers that put a load on the battery for 15 seconds and then extrapolate that to battery capacity rating.
This car is very sensitive to battery voltage and my own measured observations indicate that my charging system never fully charges the battery during local driving. You need to convince your dealer to replace the batteries and start from there, since they have not found anything obvious.
Larry

 

My first thought after reading here was battery as well. I honestly don't know what all they have/haven't done since Thursday right now. I didn't replace the battery myself before all of this because I wanted to be sure that's all it was while under warranty and the two closest parts stores to me didn't have the right one in stock and I didn't feel like waiting for it.

I agree with you on the critical thinking and it seems that techs these days have become more of the plug in, read code, put code in computer, do whatever it says for the code and nothing more. They don't look at it as a symptom of something larger and just keep fixing each symptom until you either give up or they eventually find the main cause of everything. Granted, this is my first time dealing with this service department so I don't know that's how they are, but I've heard stories that is what's happening in most service departments these days. I really just wanted to make sure it wasn't something like the alternator since I got stranded in my first Mustang because of a bad alternator (and the first replacement was bad, and then the next one my now ex-husband plugged in backward and I was stupid and didn't double check his work before going out for the evening with friends).

 

 

That was kind of the beginning of the end for us. This was before we had cell phones like today and after the cops pushed my car out of the road for me, they called him to come get me and I got to do the "walk of shame" dressed for a club as the people in our complex were leaving for church.

 

[QUOTE=PBBarb;1900598

I agree with you on the critical thinking and it seems that techs these days have become more of the plug in, read code, put code in computer, do whatever it says for the code and nothing more. They don't look at it as a symptom of something larger and just keep fixing each symptom until you either give up or they eventually find the main cause of everything[/QUOTE]

Exactly right...they have been trained to let the computers tell them what the problem is instead of using common sense and experience. In most cases this works reasonably well but sometimes they are using a bomb where a fly swatter would work. Occasionally the replacement of a ($$$$) component does fix a problem but it is the simple act of unplugging and reconnecting which cures the problem!

 

Not sure how I missed this comment earlier, but I did. The part they replaced yesterday was the junction box that does something with the two batteries. The reason they kept my car overnight was so they could test it again this morning after it sat all night. They did say that they tested everything before doing the test drive where the fault happened again, but I don't know what all they found other than loss of voltage between battery and alternator (they didn't say where or how much of a loss). Maybe they think there is a drain elsewhere and are looking for it? I have a feeling that we are at least heading in the direction of battery(ies) replacement and possibly for good measure the alternator, but I haven't actually been told that. Of course all information is being relayed from my service advisor, so I won't have full details until I get my car back and the paperwork that has been generated, but I will keep y'all updated and I did mention the battery again. All of this reminds me, I need to get a battery minder/tender (whatever they are called) ordered and will just run the extension cord for now so once I get my car back I can at least do that to hopefully prevent future weird battery issues.

 

My point is that if they let it sit in the lot all night then drive it into the service bay, the test is no good, for the fluky kind of problem you are having. However, if they let it sit in the service bay all night, then popped the hood and did the test before starting the engine, then they did the right thing.
Larry

 

 

I didn't have a chance to ask about the point you made, but got an update that they are replacing the alternator today. Honestly, if everything goes fine and I get her back without a new battery, I'll probably go ahead and replace that myself anyway along with getting a maintainer/charger ordered. I mean, yes, I'm frustrated at not having my baby after a week, but at the same time, at least they are being thorough and not just slapping a "fix" in and having to do another trip visit again in a few days. Patience is not one of my virtues, but I'm trying. At least I have a new toy (motorcycle) at home to ride around the neighborhood in the meantime.

 

Does anyone know where the secondary battery is? I'd like to replace both of mine before the end of the summer as they're original to the car and I'd prefer not to find out there's an issue when I go to start it on a chilly winter morning in Boston.

 

I haven't looked, but I think I remember seeing that it's on the other side of the trunk from the main battery. Which makes me think of another question - if I never use the eco start/stop function, do I ever really need to worry about that battery? Isn't the second one just for that?

 

If I had to guess its probably on an isolated circuit for the starter -- so removing it will kill all starting abilities...

I'll dig around the trunk this weekend when I have a spare minute -- would like to replace both before I strand myself somewhere without a jag dealer.

 

Look for the appropriate thread for all the info. In summary, 2016 and later models did not have a second battery. If it exists, the second battery is on right forward section of the trunk floor. If disconnected, it merely disables the ECO auto-off feature. The car continues to start like any other car.

 

As you've heard, these cars are quite sensitive to battery voltage. The 2nd battery is there to hold up the bus voltage to all the electronics while the starter battery restarts the car. Don't know what they do in cars without the 2nd battery.

 

 

Geez Lance, how many drinks have you had!
Hard to figure out what you meant but I'll have a stab at "ECO won't shut down the engine unless the battery is at full charge".
Either that or your predictive text needs throwing out!

 

They should be checking the battery first and foremost. Any time there is an electrical fault/problem, no matter what it is, JLR is going to look for evidence of a battery test. If its proven to be good, then they move forward with checking codes, etc. If its bad, then its replaced, and continue checking the system to make sure nothing cause the battery to fail prematurely.


As for the programming for the BMS, this is done because its measuring the State Of Health of the battery, this information is stored. When the battery is replaced, the quiescent module will see the 2 different state of health values, and it may cause a code to be logged, and cause your eco stop/start not to work correctly. Programming resets the value.


With this issue - I've seen things from loose cables, to faulty secondary battery, faulty main battery and alternator.


Considering its warranty - their going to have to prove the part they've replaced is faulty, if not, JLR will kick the claim back and dealer will be paying for that part.


If you don't drive far, or only a few days a week - you may want to invest in a trickle charger and keep it connected when not in use.


Always start with the source when its an electrical problem - the Battery.

 

@ DJS


Instead of a physical secondary battery - they use a quiescent module.

 

 

You mean translator? That was kind of what I thought you meant to say as well, but I'm pretty fluent in autocorrect it seems. Of course you didn't confirm whether it was overzealous autocorrect or if you were drinking a bit too much to be posting.