Last Friday I got back my 12 XKR from the dealer with a new alternator. They also did a battery check to verify it's state of charge and state of health. Battery was at 50% charge and overall health was 80%. Car was Idling at the dealer and it read 13.7V. I drove the car home (1 1/ hr. ride) at 60-70mph on interstate roads. Had the volt gauge in the cig. lighter and also had the Torque pro running. Voltage read 12.9V until I came to the toll booths and at idle went to 13.3V. I called the dealer and gave him an update on what I was seeing. So I got home and shut it down and put on the charger. Got up Saturday and charger was at step 7 with everything OK. Mind you the temps in my garage were at 20* while outside it was 0 to -6* outside. No driving was taking place. Sunday I took the car off of the charger and did a volt check and it was at 13.7V . Got up the morning and checked voltage and it was at 12.8V which it held all night. I started the car and it went to 13.7-13.8V and stayed there even after turning on all electrical systems I could. This was better then the old alternator that they replace. I still have a call in to the dealer but all of the info I have been reading about late model alternators with CM and ECM control seem to say this is reading in range. Now I know there is a different alternator from the 2007-2009 cars and also a different control circuit. So I would like to get some live data from the 2010-2015 5.0L XKR guys If you have a few minutes can you check what voltage you are getting at warm idle and say 2500rpm. I will gather more info most likely in a few weeks as we are now getting a few inches of snow and freezing rain. All indications say I am OK but I'm coming from the old school non control module and non ECM voltage monitoring systems that usually ran at 14.2V Thanks.

 

Normal charging range is between 13.8 & 14.2 volts.
Regards,

 

Are you using a CTEK 8 Step Charger like the MUS 4.3 model?

 

I have just changed mine on a 2010 XKR and get 14.1v at idle. I measured this at the cigar lighter with a fluke multimeter

 

Yes and it sits at step 7 where is supposed to .

 

After 4 weeks of garage duty, I removed the trickle charger 4 days ago. 2010 XKR.

Today:

Prior to starting the car: 12.68 (Fluke 77)

Voltages were also checked byt OBDII (torque pro) AND by V-meter at the trunk access terminals. All voltage reads were 0.3 VDC higher on the Fluke 77 meter vs. OBDII, CM (control module)

Immediately after start: 14.0 (only Fluke readings will be listed).

After 30 seconds RPM drop: 12.24
15 min drive at varying speeds and RPMs: solid 12.26
Stopped car for about a minute: 12.36 and rising.
Restart: 12. 26
Drive back the same distance: 12.26

This is where it gets more interesting:

About 95 percent of the time when I let off the accelerator (downhill or just coasting) the charging voltage went up to 14.6 V. As soon as I got back on the accelerator, voltage back to 12. 26

10 minutes after shutting engine off 12.56.

Already have an appointment with the dealer for next week for a J056 recall. Now, I am kind of nervous if the car can make the 3 hours drive with these voltages at night with the headlights on. BTW - upon pulling back into the garage, turning the headlights-on did not pull the voltages down any further. I guess, I will have to coast a lot to send the voltages over 14.x... -.

I will also have them look at the water pump as I have gone from Max to Low in my reservoir over the past 1500 miles. Super slow loss of coolant but, it is still a loss that should not occur normally.

Car has 9K miles on the odometer.

 

I gotta admit am getting more comfortable the more I read . I have also talked to 3 owners/operators of alternator/started rebuild shops. One thing you need to make sure the dealer/shop does is to check your battery and charge it prior to installing a new alternator. I just ran another test on my 2010 Lexus. On start up the voltage went to 14.1 and then settled at 14. After driving for 20 minutes it settled to 13.9 . I use this car 2-3 times a week and it is not on a charger.After reading more about modern alternators and electrical systems the acceptable range is 13.5 to 14.5 volts . So your normal battery would be 12.6 volts at 100% charge and should hold at that for days if not in use . Also if it is between 0-20* the battery voltage can go to 12.54 and still be 100% charged.

 

My AGM battery was installed less than 2000 miles, 6 month ago. It is holding voltage fine as shown by the pre-start voltage read.

A few months ago when I came across the same low reads, followed by normal reads after a restart, I figured that Jaguar had to have some really "intelligent" battery charging algorithm. After reading your post regarding voltages with the replaced alternator, I have no confidence either in my previous assumptions or in my alternator. I have been driving the car with what ever the issues may be, without any apparent problems. Car starts after a week of being parked with no trickle charging.

 

I drove my 150 miles at night with the light-on for about 2.5 hours. The battery read 12.26 initially, dropping a hundredth of a volt every 10-20 miles. When it got down to 12.20 it suddenly went up to 12.7. That was about half way to my destination. After that the voltage kept increasing and reached 13.1 when I finally got where I was going.

Took the car to the dealer and gave him a precise list of voltages that I had encountered in my previous drive cycles. After checking the car the mechanic provided me with a thorough explanation, as well as with a copy of a Technical Training bulletin regarding the operation of Jaguar's "Intelligent Power Management System".

According to the above the low voltages that I saw were "normal". The car Battery Management System Module communicates with the ECM and controls the alternator output, including charging AND DISCHARGING. It claims an up-to 2% fuel economy improvement, due to the reduced loading on the alternator and improved battery life by avoiding overcharging the battery by constantly applying near 14 V levels, as per the old non-intelligent systems.

The bulletin lists exactly the scenario that I experienced. The BMS + ECM decides to reduce output of the alternator until the battery discharges to approximately 75 percent of its capacity. (but, never lower than 12.20V) 12.20 V was exactly when suddenly my voltage started rising. Of course, the 12.2 V was measured on the Fluke digital meter. At the same time the OBDII was showing 11.9V for the CM (Control Module).

So, looks as if my original guess for an Intelligent Charging System proved correct. What contradicted that "guess" was when Jagtoes listed voltages over 13V with the new alternator. But, as I re-read the post that was with the battery at 50 percent, at which time full charge voltages were applied.

I think that we are causing some of this low voltage discharge issues by using trickle chargers that artificially raise the battery voltage above what is considered normal. The Intelligent System responds by discharging the battery all the way down to 12.2 (11.9 CM).

One more thing regarding the use of an OBD II plug: most car manufacturers prohibit such use as the OBD plug basically connects directly into the ECM computer and can, and will, effect its operations. In my XKR I got a dash warning message once which went away when I removed the OBD plug. In my '12 XF at times my music from my plugged in thumb drive will not play, until I remove the OBD plug. So, there is NO DOUBT that the plug is effecting the electrical system and we are gambling that it will not cause some serious or permanent damage. I am sure that no warranty would cover that.

 

ax good information . I did not want to carry this thread on a never ending trip but I'll just add to some of what you had found out. I pulled my charger the other night and the battery read 13.7V right after removing the charger. Let the car sit for 24hrs and the battery settled to 12.9-13.0V. I went for a drive with the volt meter plugged into the ash tray. Ran at 12.9-13.5V and would idle at 13.7V. what was interesting was I was doing around 55mph and came to a hill and let off the gas to coast. All of a sudden it wend to 14.1-14.4V while I was decelerating. When I hit the gas it went back to the low 13V range. I had also read some articles on ECM controlled charging management and in one it also stated that because of the voltage variations having a volt meter in the car would confuse the consumer. I guess it does. So all is well in battery land. I also understand this is the reason the the cost of the 2010-2015 XK alternator is 3X the cost of the 2006-2009. I also believe the 2006-2009 normal voltage should be 14-14.2V.

 

One more thing: I recently installed an AGM battery. The mechanic and the bulletin stated that the car self calibrates itself periodically to the battery but, will not calibrate itself to an AGM battery if it came with a flooded battery, which my car did come with.

This could be an additional reason for my lower voltage reads.

 

Very interesting info. Wonder if battery life will improve.

1. Would you be able to pdf/attach that Jag technical bulletin you mentioned in your earlier post?

2. Another thought was that perhaps the CTEK should be connected only if the Jag won't be driven for a week. What do you think?

~wrair
Ruby; 2010 xk with a "flooded battery"

 

Did you pinpoint the source of the coolant loss?

 

I'll try to scan the 5 page doc and make an attachment out of it when I get home tomorrow (Friday) As far as the CTEK use, yes, not connecting it if the car is parked less than a couple of weeks is probably a good practice. My Jag batteries frequently hold up fine for even 3 weeks of non-driving.

They ran a pressure test, plus the mechanic took the belt off to check for any courseness in the water pump bearing operation and declared it Ok. He said that "minor" cooling loss was normal. Not sure if I buy the cooling loss part. They thought that it was funny when they spotted my "spare" water pump in my trunk :-). I don't think it is funny that I feel compelled to carry one.

 

Albert,
A minor coolant loss is NOT normal! the orange antifreeze will usually show itself you look very closely...................
You are correct to carry a spare WP; Jaguars have a 6th sense!
I always carried a spare SU fuel pump in all my previous 12 Jags and thus never needed it!

Keep looking for the orange leak; could be cap, something else to carry!

Cheers, Adrian

 

Hopefully the scanned Training Doc will be readable enough. Attached the first 3 pages. The last two simply says that if the car came with flooded battery, do not replace it with an AGM unit or vice versa.

After the dealer service my car was parked for 3 days with frequent door openings. When I started it yesterday, the voltage went immediately to 14.5 V and stayed there for 25 minutes, until fully recharging the battery. After 25 minutes of freeway driving the voltage dropped to 12.9 - 13.0, indicating a fully charged battery that no longer was being charged. Stayed at those values for the rest of the 100 + mile trip. So, it is for sure an "intelligent charging system".

 

Great , super and now I think I got it.