Jaguar Parasitic Test

Battery Drain Test Parasitic Drain

I performed this test on my 99 XK8 when I found that my battery was a little low.  I first tested the battery with a digital battery tester similar to the one in the link below.  The test on the battery was good so off I went to see if I have a Parasitic Drain and this is how I did it.  This test will work on any car but the Parasitic results will differ from car to car.  The attached list has information related to Jaguar model cars.

Link to a battery tester like the one I have

I opened the trunk and hood I did not open the doors but I did have the windows open.  I disconnected the battery (both cables) and connected my voltage / amp meter between the battery and the car.  I will provide a link for it but know my meter is an older version.  If you elect to open the doors because you have fuses inside the car you will need to trick the door latch into the closed door position. 

Link to voltage / amp meter

When I got this meter years ago I elected to make it universal so I used plug in connectors and installed a fuse in the event I made a mistake.  The source connectors go to the battery red to positive and black to the negative.  On the load side I used volt meter probes and connected the red to the positive cable on the car and the black to the negative on the car using small clamps to hold the probes to the cables.

This photo shows everything connected and can be a little confusing with all the test wires and my in car battery charger leads that are connected to the car cables.  I will provide a better drawing that should help.

This drawing is for this particular meter I am using and the connections will be different if you are using a standard volt/ohm meter with mille amp and amp capability.  Using a volt/ohm meter is covered in the link I provided at the end of this write-up.

This is the readings on the car when I first connected the tester at 11:21 am and the reading 12.86 volts and 1.09 amps.  I should note that the trunk lights were on and they were going to be my indicator when the car is in the sleep mode (lights out).

At 11:35 - 14 minutes later the lights went out in the trunk and the amps went down to .21 but the volts went down to 12.75 from 12.86.

At 11:37 2 minutes later the amps went down to .03 and the voltage stayed the same at 12.75.

At 11:38 the amps dropped by .01 amp and the voltage went up by 9 tenths of a volt at 12.84.

I left it connected overnight to see what was going to take place and to my surprise the amps had not changed but the voltage went down by 00.34 of a volt.  I should mention that the overnight temperature was 29.

Duration and results

11:12     12.86v, 1.09a      Installed

11:35     12.57v, 0.21a      Courtesy lights off in trunk 

11:37     12.75v   0.03a     Another unit went to sleep but not sure what

11:38     12.84v   0.02a     No change for about half hour

09:29     12.50v   0.02a     End test

Based on the Jaguar acceptable chart that I will attach the 0.02a is below the 0.03a for an XK8.  Not bad for a 10 year old car.  The last time I did this test it was down to .01 but that was several years ago.

Link to Quiescent current testing

Now I was lucky with my results but for others it may not be an easy task.  If your results are high you will need to chase the problem down.  I am going to attach a link to Youtube that will help you in the process.  Just remember that if you begin pulling fuses you will need to wait for the car to go back to sleep before proceeding.   Depending on the meter you are using added load such as lights or components like radio, seat adjustments or key on could damage it or cause it to fail.

Link to chasing  battery drain test parasitic drain



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