I have a 98 XK8 coupe with 43k. I'm continually drawing my battery down in storage. I drive the car about once every 2 weeks and have a correct 3 month old battery. I use a trickle charger whenever I park the car in the garage. Although the charger lights and my volt meter showed correct voltage (about 13v)... when I initially jumped the battery the car was dead when I turned the key. After hooking my car to my wife's car battery a 2nd time the car started. This series of events have happened on at least 3 or 4 occasions over the course of the last few years.i've switched batteries, tried new chargers, etc.
I took my car to my battery supplier...they did a complete work up on the wiring, battery, the charger and ignition:w hat they found was that everything was working properly other than the battery was depleted and there was a .3v draw on the system with the ignition in the off position.Other than the clock, I don't know what could be causing the draw. Is .3v excessive draw? What could be causing this/ How do I fix it?

 

Well in old cars this is common and, good news is that narrowing down is simple.

First connect a voltmeter across the battery to see the drain (in mA not V). Normal is about 150mA ish. Not an exact science.

Make sure car car is asleep, takes about 20 min ( internal lights should be off including trunk lights) and then start pulling fuses in all the fuse boxes, one by one, and check if drain reduces each time.

Some forum members report simple things like the keyhole cover isn’t closing so car is constantly thinking key is in and “alive.” Another said their premium music amp was always on. A common cause is late modifications, under Centre console where they’ve hacked into a permanently on power connection, rather than an ignition controlled power supply.

Good luck and let us know how you get on

 

WHOA, PLEASE STOP
I think David meant to to say " First connect a voltmeter in line (in series) with the battery". Voltage (potential difference) is indeed measured "across" two points. However, current is measured through (in series with) a conductor.
I just did not want anyone to damage their meter by probably at best, blowing a fuse, or at worst, frying their meter. Commonly, meters can handle up to 10 amps, but measuring the short circuit current by probing a current reading across the battery will more than likely result in dire consequences as the current demand will greatly exceed 10 amps.

 

Sorry - correct “correction” to my reply above. Measure the mA current with meter in series. I disconnect the battery’s ground cable at the body and put meter between the two points.

 

Lube the little metal keyhole flap covering the ignition switch with powdered graphite as a first step. That may indeed resolve your issue....

 

FWIW, aren't there 2 levels of deep sleep the car's electrical system goes through? First after 20 min, second after a day or two?

I seem to remember something about this but it was a while ago.

John

 

Below is a link to a very simple and easy way to track down a parasitic drain on the battery. Go to post #10 and review the you tube video.

https://www.jaguarforums.com/forum/x...estate-193954/

 

With no faults your car should shut down completely after 45 minutes with a quiescent drain of 30mA. As mentioned above, the ignition barrel flap is a place to check. So is the glove box and trunk lights and also the alarm chirp sounder.

When leaving the car in the garage it should still be double locked to avoid any unwanted drain on the battery.

 

I took the car to my Jaguar mechanic. Based on his testing the draw on the battery 1.5mh was correct. He tested all systems and the charger ( ctec) and found no issues. He’s did a continuity check and found no grounding issues.
Upon reviewing my situation, I could only come up with a couple of other potential symptoms.
1. The Ctec some times displays a red light in the mode display.
2. When the battery goes down I can only jump the battery directly to another battery, can’t use the remote battery poles in the engine compartment.
I’m picking the car up tomorrow. An additional ideas?
BTW: I’m out Quakertown, Pa and am using Shearer’s In Allentown. Thanks, Steve G