Yesterday, my 2005 X350 wouldn't start. Dead battery. I used my jump pack and I was on the road in only a few minutes. It had been sitting for only 7 days. It was very chilly too, but I expected I should get much longer out of my battery before depleting. I have it on charge now. It was at 12.4V. When I hooked up the charger, it showed only 60% capacity. Where did all my lovely volts go?

Does anyone know what the average discharge rate is? All the electronics that run continuously must be a fairly significant load.

How long can your car sit before the battery dies?

 

Have your battery tested at your local auto parts store to make sure it's not on it's way out. Draw after 30 mins should be less than 30 milliamps. I had the same issue twice. Once my battery was shot and wouldn't hold a charge. Second time it was a leak in my air spring causing excessive drain from the car waking up and leveling itself. I replaced the air spring and have let it sit for 8-10 days with no issues where before it would be dead after 3 days.

 

It's a pretty new battery. It's a NAPA battery and there's a NAPA dealer nearby. I'll get them to check it.

What is the current draw in the first few minutes? More than 30ma?

 

I figured out the problem.

 

What was the issue?

 

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I'm curious why you said the discharge rate, after 30 minutes, should be less than 30ma. What would make the discharge rate drop over time (besides a slowly depleting battery capacity)? Are you implying that the initial discharge rate is higher, but then decreases to something less than 30ma after 30 minutes? If so, why?

IS there any documentation regarding this issue. Where did you get your information? Thanks!

 

I've measured an average discharge rate of 36mA over a 24hr period (technically, charge rate). Some electronics does wake up, such as the air suspension, so instantaneous value can vary.
My measurement includes any battery self-discharge, which is unknown.

 

All the info, figures and testing procedure are in the Battery Care Manual. Here is a screenshot of page.


Once the car goes to sleep - 15 - 40 minutes by this page. Measured mine closer to 30 minute mark and had dropped. That was after I found the problem. Which I believe was the air spring module waking up as I had 3 slow leaking air springs. Once I replaced I have never had a issue with it sitting weeks and starting right up. However, there are many reasons you can have drain but the only way to know is to test with multimeter.

What was the issue you found for your drain?

There was a TSB No.B419-04v3 for some earlier models where the front or rear modules were waking up causing drain.

 

The modules shut themselves off (providing nothing intervenes).

 

Thanks, FreeWiFi. I had no idea there is a battery care manual. I didn't get one. No wonder I couldn't find anything in the workshop manual or handbook. Thanks for providing that chart. I understand now why the current draw decreases over time. Jesus, these things are complicated, aren't they?

My problem is the alternator/voltage regulator. The battery voltage is 12.4V. When I start it, the alternator output is 12.4 volts. If I turn off everything, the voltage goes to 12.7V. If I fully charge the battery, I can drive for hours before the battery depletes to the point that it won't start. I'm currently (no pun intended) charging the battery after each time I drive it. I have ordered a new alternator. It should arrive tomorrow.

If I had an oscilloscope, I could look at the ripple waveform on the alternator o/p. I'll bet a 50 cent rectifier diode has opened, causing an overall drop in o/p voltage. When I get it out, I'll test it. Is there such a thing as an alternator rebuild kit?

Now, the alternator replacement procedure calls for an engine lifting bracket (left), and a lifting bar - both Jag tools. Apparently the engine needs to be lifted to provide clearance for the alternator to be removed.

Has anyone done this job without lifting the engine? Can it be done?

If I do need to lift the engine, can I do it without the Jag tools? Can I remove the left engine mount and jack the engine up slightly from underneath then place it on jack stands (but not on the transmission pan, obviously!)? Is that safe to do?

 

I posted this in another thread pertaining to replacing motor mounts. But below is a video on changing the Alternator. I believe there is room to get the alternator out without taking off the fan assembly. If the original alternator is on your car I would not throw it out if you are replacing with a aftermarket. They sell a rebuild kit to rebuild the original. Some low cost aftermarkets may not last very long and would be nice to have the original replacement just in case.


if you don't feel comfortable jacking up the engine you could get the harbor freight support bar https://www.harborfreight.com/1000-l...bar-96524.html

Here is the full Battery Care Manual.

 

It just figures that Jaguar would have a battery care manual. I love their attention to detail. Thanks for that.

I would feel comfortable with using a floor jack and a pair of jack stands. I'm going to get a set of ramps so I have more room to work. Safer too.

That's a pretty decent video. It answers my question about whether or not it is necessary to remove the engine mount. I am going to order a voltage regulator from Maniac Electrical. I think your suggestion to rebuild, and keep the old alternator is great advice. The core charge on a new one is $60. $40 for a new voltage regulator. So, for $100, I can have a spare. It's very true, what you say. Cheaper aftermarket components often don't last as long as OEM Jaguar bits. Although, I've been quite lucky with aftermarket parts. The new alternator is $326, so it had better last.

 

A new alternator from Jag dealer is 900-1100 depending on where you're located and if you are buying local or shipping. Then there is the 200+ core charge. Which makes keeping the old one and rebuilding worth it. Just make sure your aftermarket is correct to your vin and good luck.