As another thought on my road trip, and I know this has been discussed extensively in other posts, but I drove 9 hours yesterday at highway speeds, let my car sit overnight and put the float charger on it today.
After 4 hours it is still in bulk mode, constant voltage and amperage. Every other vehicle I have owned would have been in float by now. This can only mean that the Jaguar brain will not allow the alternator to fully charge the battery. It must allow enough charging for daily use as most of us do not have to contend with the low battery warning, but lead acid batteries do not like to be partially discharged.
This will have to remain one of life's mysteries since I tried months ago to get an answer from Jag engineering here and in the UK. I was told ask my local dealer service and I know better than to ask them about this detail.
Larry

 

your car has an AGM battery, not a lead acid

http://batteryuniversity.com/learn/a..._glass_mat_agm

 

An AGM is a lead acid battery, not a nickel hydride, not a lithium. It is just that the liquid is adsorbed on glass mat, but the chemistry is lead acid. It needs a higher voltage but the electronics do that and my battery maintainer also has an AGM setting. Everything is set up properly, but as has been discussed before, this car's battery charging system is strange.


Larry

 

Larry,

This has been a source of puzzlement to many of us for a couple of years now. Several of us have driven the cars w/ a voltmeter plugged into the 12V port, and documented that the "battery management system" in the F-Type doesn't allow the alternator to charge the battery at the same rate that we're used to in most vehicles.

Based upon weeks of data, the usual reading is 12.1 to 12.5 while the car is running with occasional spikes in the 13s to 14. In all my other vehicles, the readings using the same voltmeter are always 13.5 -14 while running.

I experimented many times with plugging the car into a battery maintainer (Battery Tender™) immediately after my 60 mile RT commute to work, and it always took 18-24 hours to bring the battery to a full charge vs 4-6 hours on other vehicles. If the car had been sitting for a couple of weeks, it took even longer.

There must be a logical rationale for doing it this way, but I have no clue what it is. However, I never had a dead battery or low battery warning in more than 2 years w/ the car.

 

Interested to find out if this is a problem with certain model years or sub-models of the F (V6 vs. V6S vs. V8S vs. R).

I've got a 2015 R Coupe, and have not experienced any battery issues (knock on wood!). For the sake of my paint and annoyance with swirl marks, I try to drive on days with no rain to limit unnecessary cleaning. (And I like my other car too so I enjoy driving both of em...so I let the Jag rest when it rains). That said, if it's raining for 3 or 4 days I will drive my other car, then get back into the Jag and she always starts right up without issue.

Recently returned from a 9 day vacation...and she started right up without issue.

Never seen a low battery warning.

 

No, the same voltage readings been documented in all F-Type variants, and all model years. What is different is that some cars have dead and low battery warnings frequently and most do not.

There's no difference in the battery and charging systems between F-Type variants, but 14-15 cars had a 2nd battery to power the car during Eco-Mode shutdown. That 2nd battery was deleted in MY 16.

One variable that seems to come up on cars w/ problems is that they've often had something plugged into the OBDII port. Disconnecting the battery for 30 seconds and reconnecting appears to often reset the battery management system for people who have had issues.

 

Foosh and I have discussed this before. I did drive around with a voltmeter plugged in for a couple of weeks but my driving is mostly local short hops so I keep a maintainer on mine most of the time.
This was the first time I had taken a long trip and I was hoping for a different result(insanity?). But no, it still took overnight for the maintainer to tell me that battery was fully charged. I have not had any indicated battery issues, either, but I won't because I keep it on a maintainer. The puzzle to me is why JLR engineering has the charging algorithm set to not fully charge the battery, then drop the voltage. Every car and boat I have ever owned worked that way.


Larry

 

Maybe there's something in the electronics of the car that can't stand the voltage?

It would suggest a surprising architecture if so, and one that likely affects all current models...

 

I too have had my car sit for several weeks because of my surgeries and haven't had an issue with the car or any warning lights, but then last week I took the car to the dealership for an airbag light. They must have plugged something into the OB2 sensor because I went into the car on Thursday and had the charge warning message so I followed Unhingd's comments and the error light has went away and everything been fine for 4 days. Thank you Unhingd for your assistance

 

It wouldn't surprise me if the lighter is not directly connected to the battery but is instead filtered in some way given that they are rarely used for lighting smokes anymore.

An interesting test would be to connect the voltmeter directly to the battery and see what happens while driving.

 

I was going to suggest the same thing. The voltage to the 12v outlet(s) might be fixed, so a direct connection to the battery would be the true test.

 

Well, if it's fixed, why do we see the occasional spikes to 13.5-14V and conversely in the 11's at other times? The spikes above 13V are more frequent after the car has been sitting for awhile.

The other thing that doesn't synch w/ that theory is why it took 24+ hrs for my BT to bring the battery to a full charge, even when plugged in immediately after driving it at highway speeds for 100 miles or so. Using the same BT on the Jeep or Mercedes sitting right next to it took 4-6 hours.

 

I agree, it's difficult to find an obvious explanation for those observations if JLR is attempting to fix the voltage, but nonetheless a direct connection to the battery is the only way to know for sure.

While I am not fully familiar with the charging/discharging properties of AGM batteries, I know there are differences from standard flooded-cell lead-acid batteries. I suspect your Jeep is equipped with one, and your MB might as well (though there is a decent chance it had AGM too, lots of German cars use them). And a battery tender designed for a flooded-cell battery probably isn't charging an AGM battery as optimally as it could. Anyway, my point is that you cannot compare by the length of time charging takes because there are too many variables (even if the tech was the same - diff batteries often have diff capacities, for example).

 

Nope, the 1.25 amp BT is fine for both flooded cell and AGM batteries, and I know for a fact the MB has an AGM. I'm not sure about the Jeep but it tops off in the same time as the MB.

Lastly, my diesel-pusher motorcoach has two very large AGM starter batteries wired in tandem, and the same BT charges it in 4-6 hours. The voltmeter in all 3 vehicles reads above 13V all the time when running.

Lastly, you can't monitor voltage in all types of conditions w/ it hooked to the battery, unless you run very long leads into the cabin from the trunk.

EDIT: almost forgot, but my new C7 is equipped w/ AGM and also reads above 13v at all times. It also tops off after driving in 4 hrs. or so.

 

Well, being "fine" for both flooded-cell and AGM batteries is not the same as being optimized for flooded-cell or optimized for AGM. I was strictly referring to your charger being possibly non-optimized for AGM (sounds like the case).

Nonetheless, you're right, if you know your other vehicle has an AGM and the charger topped it off in a few hours then something weird was probably going on with your F-Type.

So, I decided to do exactly this. I have a good multimeter with long leads; hooked them to the battery and drove around. I also used a 12v socket voltmeter (like you were using). Ran both for several days. Some trips were short, some were long.

On my 2016 V6S, both devices showed nearly the same voltage at all times, which was (drumroll)... 14.5v! This makes me strongly suspect something was awry with your alternator.

 

Mine behaves just like Foosh. Since the alternator is capable of putting our high enough voltage, but it only does it briefly, it would seem to be more of an issue with the regulation software.


Larry

 

Or a batch of alternators had output issues. There is no way to know whether it is a hardware or software problem without first measuring the output voltage from the alternator directly.

 

Which I cannot do driving down the road, especially since, even at the battery terminals, whatever kind of voltage regulator is in the circuit first. Since I have had no battery issues, my Jaguar service department would look at me like I had two heads if I asked them to troubleshoot a non-existent problem.


Larry

 

Yep, same here, since in more than 2 years I never had a low battery warning or dead battery, so I stopped worrying about it. Obviously, I didn't have an alternator problem or that would have manifested itself rather quickly.

It has to be the way the "battery mgmt system" is programmed.

 

Fuel economy and power.

A charging alternator consumes fuel and robs power.

There are even charging systems that specifically cut out
the alternator under heavy acceleration.

For that little bit of apparent gain, the consumer will
some day be highly inconvenienced. Someone was not
thinking ahead.