I have had my car for about a week now. I noticed that the "Battery low. Please turn on the engine" warning comes on frequently when I'm just sitting in the car with the car completely off or when I'm waiting for someone and just have the radio on.

I'm not sure if this is just a stardard warning so that a driver won't run down the battery or the battery is really low. I couldn't find anything in the manual regarding this.

 

I get this once in a while. The warning is accurate and you have run down the battery. With all the electronics in the car, it takes a lot of power. If you read some of the old threads, the computers stay on while the car is unlocked and/or if the key is near the car thus sucking power even when the car is off.

Another possible source is that if you only make short trips, the alternator doesn't have sufficient time to recharge the battery given the high loads of the electronics.

Needless to say, I've had to jump the car a couple times :-) In fact, I just had to attach the trickle charger to mine this weekend because I haven't driven it since Christmas and I noticed the low battery warning yesterday. I've had the battery checked and there are no problems with the battery cells. Just a lot of stuff drawing power...

 

mine did this as well and my dealer replaced the battery. they said there was a service bulletin about battery draw. since replacing the battery and reflashing the system it hasnt happened again. you may want to check into this with your dealer...

 

Thanks. I will have the dealer check it out.

 

I had this on my car and a few weeks ago the dealer had it in and they did a reflash/update, beforehand it would show up after as little as 25 to 30 minutes of watching television while sat in the car, afterwards it now does not show up until maybe 1 1/4 to 1 1/2 hours , so much better.
Go back to the dealer and they should sort it for you.

 

Great news! Could you take a look at the service ticket and post the service bulletin number for reference?
Thanks!

 

One thing to note about these cars that have a 'Battery Monitor' system, that's the little module that is a part of the Negative Cable clamp. If you ever connect a charger or maintainer, or boost start the car, ALWAYS, repeat ALWAYS, connect the negative lead to the body somewhere INSTEAD of the negative terminal of the battery. First, when boosting, the module can be damaged; second, that module constantly monitors the battery, and also keeps track of all current in and out. If a maintainer is connected to the terminal, current goes in that is not tallied, so to speak. That can lead to a battery that has a reasonable capacity available, but shows the 'low battery, please start engine' message, because the system doesn't know it was charged!

There is a body stud right beside the battery that has the negative cable exposed by a nice big crimped ground lug. That's the perfect place to connect a charger, everything gets measured.

So much going on in these cars.......hard to keep track of it all!

Cheers,

 

I took it in to the dealer and I was told by the service consultant that this was normal and he refuse to do a reflash on it because there is no service bulletin on this model year. That is just odd for a car like this - poor design.

 

I bought my 2012 XJ a month ago. I noticed the "low battery" warning while cleaning it. I took it back to the dealer, (european motors in Palm Desert) and they checked the battery and "re-flashed" the computer at no charge. I don't get the warning any longer.

 

what is "reflashing the computer?" i had this happen to my XJ while i was putting in address information and downloading CDs to the hard drive. i just started the vehicle to get rid of the notification. I am not concerned about the notification as long as the battery doesn't die on me.

 

This happened to me.
The trunk was being opened and closed. I was in and out, so the car was
balancing itself. All this a strain on the battery. Remember, there is a bunch of 'stuff' running off that battery.

I started the car, light went out, and all was well.
There are portable small battery chargers you can carry with you just in case.
I know all these little things can be upsetting until you

~BECOME ONE WITH THE CAR~
BILL--------------------------------->

 

I spoke to our service dept on this matter there can be a few answers to the question, first if you just want to listen to the radio just press the on button on the radio that way you dont power the rest of the modules up
and you can listen to the radio. also if you leave the key in the car will its in the garage it will also drain the battery the reason way it this it does to keep the module power up, the computer think's the driver is in the car and that way you just press the button and everything powers up there are some patches that should correct this problem but we will need the last six charaters of your vin to see if they were done or not i hope this help you if there's anything else we can do to help let us know

 

+1

If the key is in the car, it thinks it's going someplace, and will not properly power down. Applies to all Smart Key cars.

 

I was told by the service tech that he reprogrammed the computer so it's not draining the battery just because the doors are open. I was also getting the warning while I was trying to program by home link (well that's a different story). I watched the tech plug in some type of hand held computer to the port in the car. It lasted 30-40 minutes. Like I said, I don't get the warning any longer after the service even if I have the radio on or the doors and trunk open while cleaning it.

 

Which dealer did you take your car to? Do you have a 2011 or 2012? Hornberg refused to do anything to my 2012 because they said there was no service bulletin on it and this was normal. I have a hard time believing that a car like this is designed to drain the battery in 5 minutes when nothing is turned on (even if all the computerized crap is on). If it is it would be a huge design flaw.

 

I have the 2012. I took it back to European Motores in Palm Desert Ca. I bought it there last month. Funny when I picked the car up and the saleperson was explaining all the interior stuff, that is when I first noticed the warning light. I asked about it and the saleperson said it was normal because of all the computer crap. I figured the battery may need to be charged. Well I drove it home which was about 100 miles and figured that should have taken care of it. I got home and was messing around with that darn homelink and 5 minutes into it with the door open, that warning light came on. I called the dealer the next day and may a service appointment. like I said, after they did what they did, I do not get the warning light any longer.

 

I think some clarification is needed here. We need to separate two issues being mentioned; one, the "Low Battery, Please Start Engine" message, and two, things that draw down the battery.

The Low Battery message happens if the BATTERY MONITOR system "thinks" the battery is below a certain charge level. If the battery is in fact good, the Battery Monitor System probably needs the Battery Replacement application run with the Jaguar Diagnostic equipment. Let me give you a scenario; car starts out fully charged and the BMS is calibrated correctly. No "Low Battery" message. Now something runs the battery down, or it sits for two or three weeks and that drains the battery. During that time the BMS is watching current in and out of the battery. So the BMS knows the battery has been drawn down..........Low Battery message.
Now, someone not aware of the BMS connects a battery charger to the battery terminals and recharges the battery. Battery is good to go, sure. BUT THE BMS STILL THINKS THE BATTERY IS LOW. It never saw the current go in the battery because the ground cable was not attached to the BODY GROUND, it was attached to the battery terminal. The only way to correct this is to run the Battery Replacement procedure to reset it so it knows the battery state of charge.

Second, any "reflashing" or "reprogramming" would be to correct something that was possibly drawing the battery excessively. There have been a few for these to shorten the time out of the audio system for instance to help reduce the power draw.

So the Battery Low message doesn't have anything to do with "reflashing".

Holein1, I would suggest asking the dealer to reset the BMS system, that is most likely what they did for Disneyman.

Good luck!

 

And this brings up another point. When you replace the battery you have to go in with the sdd(jaguar diagnositc laptop) to reset the battery monitor system(bms) for proper operation. This meens for proper operation, you or walmart can replace the battery still, but the bms has to be reset for "battery replacement"
you want all the fancy stuff it cost more later too

 

Thanks Steve. That makes a lot of sense. I will try it again with a different dealer.

 

Huh. Why in the world would Jag design a battery monitor system that determines the fitness of the battery based on the current level at the negative terminal of the battery????

The fitness of the battery should be determined based on the level of potential of the battery and the electrical "variables/configuration" of the system the battery is serving. The load on the system and the operation of the alternator produces the difference of potential across the terminals of the battery that allow the plates in the battery and the chemical reaction that takes place to produce the excess electrons and anions which constitute the "charge".

Don't understand why Jag does some things the way they do...