Does anyone know what the "resting state" battery drain is on these cars? Or, alternatively, roughly how long a car with a fully-charged battery can sit before it reaches can-no-longer-start discharge? Either I need to look for a circuit fault, or I need to buy a new battery..... Just don't know which!

 

The best way to check the battery is to drive the car to an AutoZone, PepBoys, Sears or a place like that and have them test the battery. I do not know the actual dormant load draw on the battery while installed in the car but maybe someone can answer that for you. I would still have the battery tested to see.

 

How long is your battery lasting at rest, Boomer?

 

Three or four days, sorry to say.

 

You could always try a search here

https://www.jaguarforums.com/forum/s...d.php?p=193051

 

30 milli amps or less in 30 minutes with the alarm on. remember that every time you loose power in the battery and have to jump, youre loosing approx 1/2 the reserve starting capacity. And driving a car to charge a battery does not bring a battery up to a good deep charge. Buy a trickle charger/battery maintainer. Theyre $30-40 at Northern tools and I have 3. Even 1 for the riding mower. To check for draw, you need a DVOM and a adapter to read milli amps. clip around battery cable, doesnt matter which cause current can be read on either. Then latch the trunk lid(with it open) you can read the DVOM and monitor it. Set the alarm and watch the drop, should be 30 milliamps or less in 30 min. The problem with in poor condition batteries is that they dont maintain a good voltage even without a draw. When they drop to a certain voltage(as yours may be doing) it wakes up the whole cars electrical system modules and runs the battery all the way down.....Kinda like what killed George Washington, he would have lived to see another day if the Doctors of the day hadnt blood let him and made him even weaker till he died

 

Brutal -
Wow, you mean that as the battery runs down, the current draw gets even worse?

 

If I don't plan to drive the car over the winter months, perhaps the best solution is to remove the battery and store it inside.....

 

3-4 days, that's no use. run it down with a 12v lamp (I use a headlamp and crock clips) then slow charge 3 or 4 times, if it's still loosing it, buy another. Needless to say, battery condition is critical on these cars, warnings like trac/abs/asc always follow a dying battery.

 

I suspect your battery is on its way out... or it is not being charged fully. I know that I can leave my XJ, with a 4 year old battery, sitting for at least two weeks and still start it readily. (that's the longest I have gone to date)

I agree that using a float charger is a great idea if the car is going to sit for a long time... but 4 days should not be an issue. I have and use seven Battery Tender Jr. float chargers - two on my motorhome and one on each of my quads/motorcycles. These batteries have now lasted for years without issue, when I used to have to replace at least one or two every season before I started using the float chargers.

Just removing and storing inside doesn't appreciably help. The battery self discharges and, without a float charger, will still lose capacacity each time it is allowed to discharge significanlty below ideal voltage. The best way to maximize life of a battery that has to sit, uncharged, often is to use a float charger.

For your current battery - Fully and properly charge the battery yourself, then test with a load tester (a local major parts store will do this for free) and determine whether it is still viable. I think you'll find that it's not.

 

I have left my XJR for 3 weeks without touching it and it starts right up, battery is about 3 years old

 

My car has spent its entire life in central Fl, (goldie locks country, not too hot and not too cold) and it still has the original battery. Thats going on 6 years of service and I figure that's pretty damn good. I bought a spare OEM battery from a guy who was parting out his XJ about a year ago. I keep it charged and ready to go comes the day duty calls.

I've always heard that cold weather is the biggest killer of batteries. This pretty much confirms it for me, all though I have never had a battery go this long - even here in God's waiting room.

I think I will start periodiacally checking the charge, as suggested by others, cause Murphy's Law almost gurantees failure will occur 100 miles from home and my back up battery.

 

The primary failure that seems to occur on these cars causing a draining battery seems to be the on/dimming feature on the gauge lamps. These fail and cause a very faint lighting of the gauge lamps. A previous jaguar mechanic had stated with battery drains that they would put a tarp or towels over the car to get the interior completely dark and check for hints of lighting in the gauge cluster assembly while the vehicle is off. However many components do stay on in current cars causing a minor drain in current, although not enough to effect a proper battery.

 

I replaced my battery May 2009 with a new Interstate battery, but I also just noticed that after 4 days, the battery voltage seemed low. After 4 days of below 40 degree weather, before starting the car the voltage on the dash showed just above 11 volts.

 

Actually, it is the opposite. Ask any battery manufacturer, heat is the big battery killer because the battery loses electrolyte due to gassing when hot.

The other killer of batteries, as you know with motorhomes, is repeated deep discharge with the typical automotive battery. Not deep discharge batteries, which are designed with heavier plates to avoid that problem. The tradeoff is cold cranking amps.

 

For what it is worth, I was having a similar problem.

The battery in my xj8 is less than 3 years old. About a month ago it was drained when I tried to start it.... charged it up with a trickle charger, didn't drive it for a month, battery fully (and I mean fully) drained again.

I noticed a pretty serious power steering fluid leak which I traced down to a metal power steering fluid line laying against the alternator. With car off, when I jigged the metal line next to the alternator and it was sparking. This arcing put 2 small pin holes in the power steering line - causing the leak.

Down the line, I found a rubber sleeve that had apparently slid down and allowed the power steering line to touch the alternator.

So the point of this is I believe what was happening in my case is the power steering fluid line was shorting out to a positive contact on the alternator - thus draining the battery rapidly.

I would check that the power steering line under your air box is not directly touching the alternator (i.e. the rubber sleeve is in place).

Just a thought....

 

I discovered that my car will give me no warning what so ever of a worn battery. It started fine, I drove 16 miles and picked up my girlfriend than drove another 6 miles to South Liverpool. When I came back to the car it wouldn't crank. After checking everything I could I reluctantly called the breakdown service. One jump later I was running again. Turns out the battery was the one from new. I bought a new one the next day but it is something to bear in mind.

Big battery though same size as one of the two that makes the 24v circuit on my Bus at work!

 

Just some more information to verify Brutal's comments. I am tracking down a battery not charging problem on a 1998 XJ8. Anyway, I measured the current flowing out of the battery with the all the doors locked, the trunk closed, and the hood down. It starts out at about 230 milliamps, or near a 1/4 amp, which had me concerned, but after about 15 to 16 minutes dropped to 30 milliamps (.03 amps). Apparently normal and certainly not a heavy continuous load on a car battery.