Well cool that you ruled out the ADU. If you can confirm that you have 12.6 volts resting for us, that would be great. Easiest to test in the morning when left overnight without a maintainer. 12.6 volts = fully charged battery. Anything less and it should be replaced. So consider charging it to full, then disconnect charger, let sit overnight and let us know the reading.

If it is 12.6 volts, performing a quiescent current test would be the next step to test for any drain when not running. Some guys just skip this test and consider it only after replacing the battery.

Now Jaguar does say that you should replace like for like batteries in the 2010 onward (if OEM was AGM, use AGM replacement and if standard flooded, replace with that) but they never explained why in the TSB. We have speculated that the alternator Jaguar used in various vehicles but that's not correct.

GGG offered up the reason in a post:
"The experience allowed me to discover from the Dealer the answer to the "wet"/AGM battery question which has intrigued me for some time. As we have discovered on the forum, X150's can have either fitted by the factory and this is apparently due to availability rather than any technical necessity. Only Stop/Start Jaguars REQUIRE an AGM battery. Others can use EITHER. My research also revealed that VARTA and BOSCH batteries are produced in the same factory."

 

You are lucky I think, although what you describe is the way it should be. Last year I went to a Jaguar dealer to buy a replacement for my 2004 Vanden Plas replacing a Varta battery. I was offered two types of batteries with part numbers I did not recognise, one of which said it was made in Mexico. I asked if the batteries had silver clcium impregnated lead plates which are designed to receive charge rates up to 15v at higher amp rates. regular lead plates or AGM batteries cannot tolerate such charge rates.The Service Manual for my 2012 XF states that an AGM battery should not be charged at rates above 14.8v or battery life will be reduced. The dealer let me look at all the batteries they had in stock and I found the one pictured below. This has the silver doped calcium lead plates I was looking for. I have no idea what batteries are installed in new Jaguars

 

I do not have a Jaguar label on my battery so I'm assuming it has been replaced. Had it out for a ride today. The only time the voltage gauge goes above 13 is with higher rpms above 4K, then it quickly returns to around 12.4. I don't have a multimeter, but I'll drop by a friends place tomorrow to check it.

 

I have switched the battery pictured above into my 2012 XF. I am not running the car yet so I cannot give you any battery readings after running the motor. But after taking off the automatic battery charger it shows 13.0v hooked to the car with the trunk lid open and the trunk light on. I bought the car with 2017 Interstate AGM battery which is currently sitting on my bench with a CTek 3300 connected, green light on and the same volt meter shows 12.85 v

 

I agree @Sean S . I’m one of those guys (bah ha ha;-) that takes the position of ‘why gamble with it’. Whether a sailboat or car I need a dependable battery... and cheaper than a tire, I can do that. Following a full charge, 12.6(either disconnected or all systems shut down) at the battery is a bad battery. Period.

Also, I have no need to put an agm battery in my car. The alternator and management electronics aren’t tuned for that type of battery, anyways.
But I have 2 alternators on my boat now... one for the deep cycles, and one for the starter. I’ve learned heaps about battery management and I get much longer life than most (on the boat)... just like bushings, my girl (xkr) eats batteries. Comes with the territory. I’m fine with it.

 

In the US, Jag dealers do install Interstate as replacement battery. I have one in my car, installed by the Jag dealer in SC for the original owner, and written up as such in the work order.

 

The photos below show the label on the dealer-installed battery for my F-Type, fitted (fully charged) last week. You will note that it has the Jaguar/Land Rover label - which is in French and English for Canada - and that it is distributed ("commercialisé") - but not manufactured by Interstate.
Group H8A, 850 CCA, 95AH, Jaguar part number C2D55037. There is no label visible to me to show whether it is a Varta or Fiamm (which was the brand of the original OEM battery in this car).

 

If I switch on the ignition but do not start the engine, my voltage on Bob's ADU reads 12.2. When driving it reads about 13.7 typically. The car is on a CTEK when not being used. Never had any issues with codes or with the battery at all. Recently I took the car to France and it sat in the hotel parking lot for two weeks, never moving, no CTEK, and it started perfectly when it was time to drive home. I am happy to believe you when you say my batter is 'bad' but if it is, I don't care, as it is not causing me any issues at all. Generally speaking, I don't sweat small stuff - ignorance is bliss I guess

BTW, the OBDII reader Bob provided with my ADU switches itself off completely after a short period, so it is safe to leave it connected. Like MarkyUK, mine has been connected ever since I got the ADU and seems to give no problems. Other OBDII readers may stay alive all the time of course.

EDIT: My ADU and my Torque Pro readings are all identical.

 

Yep, your comments are duly noted and your undying love for the ADU is as well. DGL noted too that his Torque Pro readings were identical.
Still, the resting voltage should be checked at the battery. So thanks for the smarmy comments. I'm happy for you and your blissfulness.

I'm trying to help the OP as are others on this thread. He's showing what the ADU reads. He doesn't know how old his battery is and he's concerned because he doesn't want to get stuck with a dead battery.

I and others have suggested he check the resting voltage at the battery. I'm not trying to explain the gap between his ADU readings and proper battery voltage.

 

What a very strange reply. I do not have an 'undying love' for Bob's ADU, nor indeed for any mechanical or electrical item. But I do appreciate the exceptional usefulness of it, and the creativity that went into designing and creating it. I am not alone. Everyone who has been fortunate enough to acquire one of these terrific additions to their XK says the same. How you arrived at the conclusion I was in love with the device is something only you can explain (to yourself please as I am not interested).

I would expect the Torque Pro readings to be identical to the ADU readings, since they come from the same source, the OBD port. I mentioned it because some doubt was raised as to whether there could be a discrepancy. My post adds another datum point to the information, that is all.

I think you may have misunderstood the meaning of 'smarmy' which is defined as "ingratiating or wheedling in an insincere manner". I think you may have meant to say 'snarky' but it is of no matter since I was intending neither and, from any normal reading of my post, neither could even be inferred.

I noted your earlier, sensible, remark to check the reading at the battery, and made no comment on it. I agree with you as it happens. My purpose in posting was to provide another datum point with regard to your assertion that a battery reading below 12.3 at rest was 'bad'. I even agreed with you that you may well be correct but also wanted to make the point that even a battery which is reading 12.2 at rest (at the OBD port) is causing no problems whatsoever. My car is throwing no codes, is starting first time every time, has stood for two weeks without the CTEK and again started first time, and is driving perfectly. I doubt that my car has any special or unknown properties, so it is likely that others seeing the same at rest reading at the OBD port may also have no problems. To assert to them, categorically, that their battery is 'bad' is not helpful if it causes people to consider replacing a battery that may be 'bad' by your definition, but which is otherwise performing perfectly properly.

One of the benefits of forums is that they allow an exchange of information and alternative, even opposing, views. The different experiences of different members is always valuable since it gives a variety of perspectives. In this case, your perspective is that my battery is 'bad'. My perspective is that it is not (working on the basis that the car is performing entirely properly with this battery). We may both be right or neither of us may be right. That doesn't matter to me, as I am not trying to win some sort of pi$$ing contest with you, as you seem to believe. Just giving a different perspective, which, in this case, is a valid thing to do.

I have always enjoyed reading your insights into the past, and am the first to acknowledge that my own experience of, and expertise in, mechanical (etc) issues is considerably less than that of many other members. I do not understand your somewhat offensive post, but I can assure you I won't lose any sleep, or expend any time, in trying to do so.

My final word on it is the same as in my original post which seems to have rattled you: my voltage at the OBDII port is 12;2 and my battery is nothing like 'bad'.

 

You can monitor the voltage real-time in your car's display by pressing a few buttons prior to starting the car...

https://www.jaguarforums.com/forum/x...n-menu-193739/

 

If your battery is at 12.2 volts it is less than 50% charged. As I’ve said before voltage is not everything...capacity is critical for being able to start the car and operate electrics.

https://www.aa1car.com/library/2003/us20310.htm

 

Can some other members with 5l, 2012-2015 chime in and give ADU or torque pro voltage readings. There seems to be a difference in the 4.2l and 5l models. Maybe the PID parameters should be different for the 4.2 and 5l models to give accurate numbers. Also the 5l models have the BMS for the alternators. It looks like my BMS 5l 2014 is displaying around 1 volt less than 4,2l models. I have no problems with my car in any way. I've disconnected the battery maintainer to see if it will make a difference.

 

Now a little colder here in the UK by 5c than my first post in this thread and my ADU is reading 12.6/7 without start and 13.1-13.4 with engine started and no electrics (except my tracker and dashcam) running, drops to about 12.9 with lights, stereo, heated seats/wheel when driving with my foot on the gas. If I coast for a period over 5 seconds it rises to 13.1v

That said I have my battery on CTEK charge once per week and it is a higher output/strength type 019 than the stock OEM battery (type 017?) that came with the car.

 

I have both so I'll have a look tomorrow but I really could care less what the OBD says as I've found it to not match what the VOM says...

 

barnsie, you’ve misunderstood what Sean W is asking of the OP. He is asking for a reading of the voltage when the battery is at rest, i.e. no load. When you turn on your ignition, or simply open the door and put the car into convenience mode, there is a load on the battery and it will read a lower voltage than when it is at rest.
To get the at rest reading, either disconnect the battery, or leave the trunk/boot open until the car exits convenience mode (and the trunk/boot lights turn off), then measure with a volt meter. Your 12.2 with ignition on, is probably fine, but can the OP’s battery maintain a full charge with no load, that was the question.

 

I was going to say the same thing. The voltage reading with the ignition on is not the same as reading it with nothing on. To check it with absolutely no load, the ignition can't be on. Like I said in a previous post, a digital multimeter directly on the battery is the best way to get the true voltage reading. ODB ports will be off, and it depends on the vehicle by how much they will be off. If I went by the reading from the ODB port in my Porsche, I would have replaced both the battery and alternator already.

 

My battery is permanently on a CTEK when the car is not being driven. The CTEK indicates the battery is charged OK. No battery problems of any sort. But the OBDII port reports 12.2 with the ignition on and and the engine not running. It's not a problem for me because a) the car is working perfectly and b) I know I can leave the car standing (no CTEK) for two weeks, also with no problems of any kind, as I proved in August on vacation. The main thing is that, in my case, the car is 'able to start and operate electrics'. What more do I need?

If the car starts to misbehave, and the battery might be the culprit, it's pretty easy to go get a new battery. Up to that point, what would be the purpose of spending the money?

 

Thanks - that is a useful contribution to my understanding and ongoing learning process here. I can easily believe that I misunderstood something. It may have been better if Sean W had explained that I was misunderstanding him, rather than launching a personal attack, but hey ho....

 

we good Barnsie?