This is a pretty wonky question, but I'll give it a go...
What is the allowable milliamp draw on the battery when a 2000 XK8 is just sitting?
I measured mine and found 1.4 Ma.
The reason I'm asking is because I just replaced a pretty new battery under warranty. It went dead unexpectedly once a few months ago, then twice this week in mild weather. It could have been a defective battery easily enough but I'd like to know if my static draw is above normal...if there even is a normal amount.

1.4 milliamps doesn't seem like much, but I really don't have much perspective.

Can anybody help?

Regards,

 

The quiescent drain on your car should be 30mA after the 45 minutes. I don’t think you are reading your meter correctly.

 

Thanks, I will check again. Key Off. Meter set to mA, positive cable disconnected, meter leads between the battery post and the positive cable. Right?

My meter reads 1.4 mA instantly. What's the 45 minutes about?

Thanks!

 

45 minutes is the time Jaguar states the car will take to fully shutdown and go to sleep. You are correct in the way you have connected the meter but I have never seen a reading that low, which is why I question it.

 

Well, I need to correct a couple of things. My meter input setting for one. And, I see that others measure on the Negative side, I did Positive.

I'll clean up my act and try again. Thanks.

 

I did a test today. When the car is buttoned up and locked there is a moment of high current, several amps, when relays and door solenoids are actuated. Then the current drops to 600ma and continues to drop until about 60 seconds, where it stabilizes at 300ma. It stays there for about 15 minutes, when it suddenly drops to 60 ma. Eventually it stabilizes at 30ma at the 1 hour point, which matches the Jag spec.
I did the test twice with two digital multimeters with the same result.
So the car is busy for an hour. I'd love to know what it is doing, but mere mortals may not be privy to that knowledge.

 

Educate me on your meters please. Mine have a setting for milivolts but not for ma. What am I missing? Great information...

 

Current flow should be the same whether measured at the positive or negative battery terminal. The advantage of using the negative terminal is that it is safer to disconnect and connect the negative cable, as if the wrench on the negative terminal, or the loose negative cable itself, touches the car's metal, nothing will happen. The positive one, however, can melt a wrench.

If your meter does not have a ma, or milliamp, setting, how did you measure the 1.4 ma stated in your original message? A true multimeter is often called a VOM, or Volt-Ohm-Milliammeter. It measures potential difference in volts, resistance in ohms, and current in amperes. Many meters will not range to amperes, but only measure millamperes, as higher current flows can melt probes and small wires. That is why the standard term for a multimeter is VOM instead of VOA.

 

My inexperience with the meter let me measure something other than mA. I've studied up on all that and found the hidden process on this meter to measure mA properly. I understand about measuring on the Negative side, thanks. I'll give it a try here tomorrow.

In the process, though, I saw an interesting YouTube video. The fellow on that video measured millivolts at the fuse box using the ends of the fuses and then converted that value, through a chart, to milliamp draw. The advantage is that you do not need to break into the circuit and potentially disrupt the status of the various modules. There was also discussion about latching and locking the doors and hood and trunk so that those relays are not powered up.

Thanks for your clear write up!

 

Scott don't forget to move your lead's connection from volts ohms to ma receptacle.

Sounds like you're new to this so heads up: Move the lead back when you're done. Ma receptacle intentionally offers zero resistance to com (the other receptacle). Works great for amps, but if you forget to repeat the plug you'll get a short circuit next time you try to read volts or ohms!

John

 

Indeed!


I figure the fused, up to 200 mA is correct, no?

 

Well, depends. The quiescent draw should be under 200 mA, but the transient draw before the car settles down, can be well over 200 mA, tripping the fuse. You might want to use the other one depending on what you are measuring (i.e. all the way from on to quiescent).

 

You are correct! After all that and help from everyone I figured out that the car shuts down normally. Good news, my battery was evidently defective...

I spent some time with the meter manual...learned a good bit about Auto Ranging and some of the less frequently used dial settings. Now if I can remember most of it's!

Thanks all, great forum as always!