2013 XJ Battery Maintainer Installation
 

For MY 2013, Jaguar introduced its "Intelligent Stop/Start" system on XJ and XF models. That system incorporates a second, auxiliary battery to restart the engine after it has been stopped, for example, while waiting at a stop light. Connecting a battery maintainer directly to the main battery positive (+) and negative (-) terminals can cause damage to the electrical system. The negative (-) ground connection must be made directly to the chassis, and not the main battery.

The auxiliary battery is at the top right. Note that I used the CTEK alligator clips (with the pigtail and black and yellow quick connector) and that the red clip is connected to the main battery positive (+) terminal and the black clip is connected to a ground on the body. Those clips are very strong.
https://www.jaguarforums.com/forum/a...1&d=1415600254

Here's a close-up:
https://www.jaguarforums.com/forum/a...1&d=1415600458

Next, I closed the floor panel and fed the pigtail with the quick connector exposed above the floor, ready to be connected to the CTEK.
https://www.jaguarforums.com/forum/a...1&d=1415600507

Here's is the connected pigtail. Note that I fed the wire under the weatherstrip and tail light, which allows the trunk to close completely without touching that wire. I keep the CTEK unit outside of the trunk since it gets hot while in operation.
https://www.jaguarforums.com/forum/a...1&d=1415600630

And a close-up:
https://www.jaguarforums.com/forum/a...1&d=1415600891

With the trunk closed:
https://www.jaguarforums.com/forum/a...1&d=1415600940

With the CTEK unit perched on top of my right rear tire:
https://www.jaguarforums.com/forum/a...1&d=1415601007

Works great! My CTEK is model MUS 4.3, which is an 8-stage charger and is an upgrade over the 4-stage model 3300.

Hope this helps!

Stuart

Good write up. I did a similar connection but I used the other connector where the live bolts straight to the battery and the negative bolted to the chassis Earth point. Minimises the likelihood of maybe the crocodile clip coming undone.
I only have the one battery as it is a 2011 model but I
I haves been using a ctek from day 1.

I have a BatteryMINDER brand maintainer for my 2009 XKR and use the supplied alligator clips to connect to the remote battery terminals in the trunk. Those clips have held tight for over 2-1/2 years of daily use. The CTEK alligator clips are much larger and stronger and I doubt they will come undone. For background and details, see my posts ##17, 19, and 21 on the New XK/XKR forum: https://www.jaguarforums.com/forum/x...s-73471/page2/

I keep both of my Jags plugged in whenever they are parked at home. Just got the XJ, and haven't had any electrical gremlins in my XKR. I credit that to always locking the doors and keeping it on the battery maintainer. I'll do the same with the XJ.

How to Charge the Auxiliary Stop-Start Battery
 

Does anyone know if the CTEK as I have it installed to the primary battery, per the above pictures, also simultaneously charges the small stop-start battery? My stop-start hasn't been working as frequently as it used to, and I'm thinking that the auxiliary battery might not be fully charged. What should the minimum voltage of that small battery be with the engine off? That auxiliary battery was replaced by my dealer (expensive critter!) less than a year ago. I use my CTEK almost every day, as most of my driving is short trips around town, and very little highway, and it starts right up every time.

I'm thinking of attaching my CTEK to the auxiliary battery, but am not sure if I should attach the negative lead to the battery post or to a chassis ground. Or if it makes any difference with that battery.

I think your right Stuart. The little battery is not in the circuit until the engine cuts off so I can't see any way you could charge it thru the big battery.
Otherwise if you ran the battery down it would kill both batteries.

I think your right again that the battery monitor is attached to the big battery only.
You don't get any dash board lights when the little battery is low just the ECO function stops working but you do if the big one is low.
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CTEK Works on Auxiliary Stop-Start Battery
 

Last night I hooked up my CTEK MUS4.3 to my small stop-start battery using the alligator clips, with the red clipped onto the + positive battery terminal and the black clipped onto a chassis ground as pictured below. I attached the power lead, plugged the CTEK into the wall outlet, and set the CTEK to the small battery program indicated by the motorcycle icon. The CTEK went to Stage 2. This morning the CTEK was at Stage 7. It appears that the small battery was quite discharged, which is why the stop-start wasn't working properly.

CTEK Hookup
https://cimg0.ibsrv.net/gimg/www.jag...c79a97836d.jpg

Stage 7 and Small Battery Program
https://cimg2.ibsrv.net/gimg/www.jag...a5cfde131d.jpg

I decided to leave the small battery alligator clip pigtail attached and routed it into the trunk, where I also routed the main battery pigtail. This makes it quick and easy to charge either battery.
https://cimg1.ibsrv.net/gimg/www.jag...c43cff40c5.jpg

I can't take my XJ for a test drive right now as all 4 wheels are off the car and being refurbished. I'll have them back tomorrow and will update this thread and let you know if the stop-start is now working properly.

I have a work van with two batteries, not for start stop but one is used for starting the vehicle and the other for accessories. They are both the same size batteries. I have rigged up the bolt on connections to each battery as they are mounted under the drivers seat and if the van is not used for a while, say over a Christmas holiday , then I connect a ctek to each battery

My solution was much simpler. On my battery minder, it has an option to plug in an OBD II adapter, so I purchased that and then I just crack the driver window and run it thru that, plug into the ODB II port and it works. I garage my vehicle, so having the window cracked is no issue.

I have seen those before and have not been able to find any amperage rating?
Not sure you can change or how much you can charge thru the OBDII port?
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SUCCESS! The stop-start system now works perfectly! All it needed was for the small stop-start battery to be charged.

Note that the XJ primary battery is an AGM battery, so the CTEK must be set to the cold weather mode (snowflake icon) for the proper charging profile. The normal mode (car icon) is for conventional, "flooded" batteries, not AGM. The motorcycle icon is for the small, secondary battery .

For the XJ stop-start system to function properly, the primary battery needs to be fully charged as well as the secondary battery. If either battery is weak, the stop-start won't work.

Update and correction: CTEK Customer Service told me to use the normal mode (car icon) for my AGM battery, except when the temperature is below freezing.

Doesn’t sound right to me. AGM needs a higher charging voltage.

Here's the document from CTEK:

https://cimg7.ibsrv.net/gimg/www.jag...4794230569.jpg

The charging voltage is less critical than the float, as it spends a short time charging, and a long time at float.

Does the manual say anywhere what the float voltage is? A lead acid battery requires about 13.4V during float, while an AGM requires more - 13.8. If you leave an AGM long term at 13.4V float voltage, it will be a little undercharged - at about 90%. The rule for lead acid batteries (including AGM) is that uncharged capacity gets lost to sulphation, so with time you'll lose 10%.

Given that one point of having a battery tender is to prevent this from happening, it seems like a good idea to use the correct profile. Simple question for CTEK, does this charger have the right profile for AGM, or not? If not, get a charger that does.

Here's a reference by Rolls, probably the most reputable manufacturer of batteries there is :

AGM Charging : Technical Support Desk

The ECO battery has been replaced multiple times under warranty as well as the battery module the monitors/controls the battery system. A few months ago the ECO light came on indicating the battery had failed again. I finally got around to connecting the CTEK MUS4.3 (it's a DD so no time to take it down for however long it takes to charge the aux battery). The power light came on the CTEK but nothing else unlike when I connect it to the XKR where it automatically selects the correct battery and goes through the steps. I manually selected motorcyle for small batteries and after a while step 1 (desulphinate) finally lit up. After about 15 minutes though the light went out. I restarted the process and this time step 1 has remained lit for some time.

Anyone have experience with this?

Hi jahummer,

What year and model is your XJ and when did you get it? I didn't realize that you have one as it's not in your signature or Personal Profile. I'm pretty sure that Jaguar changed the Stop-Start system some time after 2013, so my comments below might not apply to your car.

See the CTEK SupportMail in my Post #14, above.

Try the normal mode (car icon) instead of the small battery mode (motorbike icon). My OEM auxiliary battery is rated at 14Ah and I've used it with no problems. Note that Stop-Start won't work if the primary battery is weak. I keep both batteries topped up and alternate the charger between them.

Stuart

thank you everyone