Good day y’all,

Was going to perform my ritualistic wash and wax today when my XK refused to start. Checked the battery voltage and it reads 5.4…..that is a terrible read. I haven’t left anything on, I double locked the car with Fob. And I bought this battery brand new at AutoZone back in March.

Battery type is Duralast Platinum-AGM H-8, I currently have it connected to my battery maintainer so let’s see if it helps by tonight, tomorrow.

Thoughts?

 

Could be the battery failed (doesn't happen often) - could be some high parasitic drain on shutdown. How long was the car stood for?

 

You will need more than 1-2 amps under these circumstances.

 

@indyx358. If you have anything plugged into the OBDII port, remove it after you turn off the ignition. Leaving it plugged in could cause a battery drain.

You stated: "I double locked the car ... ". Actually, you didn't.

All USA market JLR vehicles have double-locking disabled from the factory, as it violates US law. If you try to "double lock" your X150, you will get a "beep beep" from the sounder, which is an error message that means your car is not double locked. Double locking prevents the doors from being opened from the inside, as well as the outside.

Double locking is not available on USA market vehicles because the National Highway Transportation Safety Administration deemed it to be unsafe. Double locking is popular in Europe because it makes cars more difficult to steal. However, because the doors cannot be opened from the inside when double-locked, a small child or other person can be trapped inside and die from extreme heat.

Visual confirmation that your car is locked is that your side mirrors have automatically folded in, unless you disabled that feature or your car is not equipped with it.

For more information:
See: NHTSA January 2009 Double Locking

Stuart

 

Thanks for the clarification Stuart. My XK is not equipped with auto closing mirrors. Nothing plugged in the OBDII port and car only sat for 2 days prior to this surge….

im currently waiting to see if charge is held after some time on the maintainer.

 

If you leave your Smartkey within 10 feet of your XK, the car will stay in Convenience Mode longer and could drain the battery.

Even though you bought that AGM battery in March 2024, you don't know if it was fully charged when installed or how long it sat on AutoZone's shelf discharging before being installed. Drive back to AutoZone when you can and have them load test your battery. They may decide to replace it under warranty.

Another possibility is that you're not driving far enough every day for your alternator to fully charge the battery, or the alternator isn't charging. See: Alternator Not Charging

Don't randomly throw new parts at your car. Get the Diagnostic Trouble Codes and follow the troubleshooting guide.

Good luck!

Stuart

 

Much appreciated - now you’re making me nervous. I’m going to take the battery in for recharge/replacement under its warranty. Once I get her started I’m taking her straight to my tech to check the alternator and proceed from there. 😭

 

i humbly disagree. If the car was in convenience mode for 20 mins and if that caused the battery to drain to 5v, the battery was on its last legs anyways.

Furthermore, your particular car does not call for an AGM battery. No, I am not saying that would be the cause of the failure.
But you could save some money and put the specified battery in the car. And get the same life out of it.

 

If I had to return the battery to the vendor, I wouldn't leave the car without the maintainer operating. AGMs can suffer discharging with less ill effect than wet cells.

 

@indyx358 If you like what a Forum member has posted, simply press the . button at the bottom right of the page.
​

 

Well I fitted a new alarm sounder and now my battery will hold its charge for 3/4 weeks and it starts straight up no problem before I changed the sounder same battery would be dead after 4/5 days I have a 2006 X150

 

And they have become popular in the antique/classic car hobby because old cars tend to get driven barely around the block once a month or less. You didn't mention what kind of battery maintainer you have but want to make sure the one you've got is up to the job. Modern cars tend to draw more current with the ignition off than antique/classic cars. You want to have a unit capable of keeping up with the maximum current load that the car is likely to draw if you accidentally leave the door open. There's lots of inexpensive maintainers at 1 to 2 amps, but those are intended for your old E-type because the most its likely to pull is a dome light. There are some that are less than an amp but those should only be used on a regular battery that is disconnected/isolated by a switch. But the modern car has a bunch of computers that might not shut down and you don't want to disconnect the battery (lose all the memory), not to mention more features than just a dome light that might stay on. Thus you want a unit that's going to provide closer to 4 amps. AGM batteries also tend to do better with a higher maintenance voltage so you want a unit that's got an AGM setting. Offering all this in hopes that the only problem was that the new AGM battery was connected to a puny little Battery Tender Junior and can be resolved simply with a more capable unit.

 

Got the battery replaced under warranty without question so now I’m going to monitor its performance. Old battery was at less than 30% even after plugging it in overnight. New one is at 90% so it’s going to get fully charged and I’ll take it to my tech to test the alternator this week. Cheers all!

 

Does anyone else care to discuss the possibility that the sound bat might be the cause of so many dead batteries?
I never considered the clunk sound of the locks should also have a 'chirp'
Mine has never chipped and the battery has always been a monitored concern for myself. (Watching it slowly drop.)
Wj

 

Care to share the part number for the alarm sounder?

 

I think this is it, but I'm not positive.




​​​​​
Yes, I know this thread is about dead batteries, but my reply above was not intended to be a pun.

 

Hey Guy,

what is the specified battery type for my 2007 XK N/A?

 

Hi
I recently had the alarm sounder replaced and now the battery does not discharge and the alarm chirps on locking.
the receipt shows part number C2D47174
The picture of the part shown in another reply is just the normal horn and not the sounder.

The sounder is beneath the bonnet airbag and because of this i decided to have it done at the dealer, however it is a relatively easy diy for most people.
Apparently this unit has an internal battery and when it fails the car supplies voltage continuously from the main battery causing discharge and eventually battery failure.
Part from Jaguar was £120 plus fitting.
Hope this helps.

 

deleted

 

This sounder is the same as a Ford Fiesta .
Probably save some money.
The Chirp is programmable but not by a User. I think by SDD only.