I have a 2008 XK convertible. I did connect a CTEK harness to the battery pole and frame in the trunk so I can plus in the tender if it’s going to sit an extended period.

the problem is if I don’t drive it for 4-5 days, I am still able to start it but some things the car shuts down until the battery gets charged enough to run them.

I've had the battery checked twice and it’s perfect. What part in the car could be draining so much battery in such a short time? And, is there a way to test and determine what it is?

I think something other than the battery may be wrong.

Thank you
Craig

 

Is the ground lead of your CTEK connected to the OTHER post which is covered with paint? There are two threaded posts in the boot bottom area, one has paint the other does not. The unpainted post is the true ground. The other may work, but isn't really a good ground point.

 

Surely, without a complete circuit the lights on the CTEK won't illuminate?

A Google search for "parasitic battery drain" will give you loads of ideas on how to find the culprit causing your problem

 

Check out this vid, shows a nifty battery drain checking gadget in operation: Perfect to diagnose the cause of the drain if you can find a shop which has one.

 

That is a neat gadget to ID the circuit causing the drain. Much better than pulling fuses in the various fuse boxes. 👍
Hard for me to bend enough ways any more to get to the one in the footwell!

 

Since it's a first gen without BMS, why not connect directly to the battery terminals? Also what makes you think the battery's ok? Have you tried using a proper 10A charger and not a tender/maintainer? How old is it?

 

Here's a thread which may help you. There is a discussion on how best to connect up a CTEK MXS 5 with various options, including the one which I chose to do including photos of what I did - https://www.jaguarforums.com/forum/x...tainer-156331/

My CTEK has been working perfectly using this setup for the 6 years since I installed it with absolutely no problems, even after changing from a 'wet' battery to an AGM, although my SDD software was updated to recognise the AGM and adjust the charging rate accordingly when being driven.

My 2011 XKR convertible has the Battery Monitoring System (BMS) on the negative terminal of the battery, hence I could not connect the CTEK eyelet directly to it although the 2008 XK does not have BMS.

With all the electronics on the XK, including the alarm/immobiliser, there is a significant drain on the battery even when the car is just sitting there locked, and unless you do a decent regular mileage, it is quite possible that the battery will be flat even after only a few days. How far do you travel when you do use it? Depending on the condition of the battery, it needs a run of 30-40 miles to put any meaningful charge on it, and for a couple of hours driving to recharge it fully. Is your alternator working OK and doing its job in recharging the battery when you are using the car?

 

I can leave it for weeks, unlocked without the CTEK connected and have no issues with verified good battery. But once your battery begins to fail, it may no longer hold a charge, even if it shows adequate voltage.

 

I leave it for months. Unlocked. No maintainer. No issues.

 

I hooked up an ammeter to my 07 XK NA Coupe, on the negative line of the battery. With key on, pre quiescent, draw was about 9A . Quiescent current after shutdown was about 250 mA, or 1 amp every four hours. Enough to be a meaningful drain over 5-7 days. Of course, this is not assuming a recharge by driving in the interim. Found that if I shut off the climate at the screen when I left the car the drain dropped to a very acceptable 14mA. Also made a habit of double locking the key on leaving. No idea if this made any difference, but others here swore by it.

BTW, my XK has a shutdown time of 3 minutes when the car was locked. Also bought an AGM battery about the same time.

No problems since. No idea why the Climate system had this effect. Once I found a workaround by shutting off Climate, I didn't dig any deeper.

 

I've done this for over 20 years on every car, in fact I've everything turned off before shutting down as I believe it's best to have as little load as possible when starting the car.