My 2007 XK 4.2 is in (almost) daily use. 136k miles and mostly good but she’s developed the bad habit of fully discharging if left to her own devices for a week or more. I do remember seeing a post a while ago, saying that a certain part is the favourite for causing this problem………but can I find it?! Directions to that post would be most helpful please and all other suggestions gratefully appreciated. Battery is only 18 months old and journeys are seldom shorter than 10 miles or so, so charging should (?) be ok.

 

I have the same problem with our 2006 XK. I think the discharge might be something to do with the alarm sounder which no longer has a functioning battery so is drawing on the main battery to try and keep it charged. However, I'll also look forward to information about what to do to fix it.

Richard

 

Threads about
quiescent current
have lots of useful data & ideas.

Some are about other jags but can still be very useful.

 

True enough, the quiescent drain should fall within specs. The specs are in the workshop manual.
But... is the battery just old?

Also, in the modern age, think of an alternator as a "maintainer" not as a "charger" and you'll be happier for it.
(As in "Why" do so many cars now come with a factory battery maintainer installed?)

 

I use the 2 amp trickle charger that is easily installed by the taillights. When the battery is full the charging light turns green.
Good in the winter months.

 

When I checked mine years ago the drain when everything settled down was around 6 milli-amps. I've never needed a CTEK maintainer, though I do use one on my boat.