Ken, in all my years of chasing sparks, I've never really had to worry an "operating drain". If the alternator is keeping the system fully charged, the energy consumption level isn't really a problem.

If you had a single circuit drawing an excess amount of current, that fuse will blow, so that would be apparent right away.

If you have multiple circuits drawing a lot of current collectively, but none individually bad enough to blow their respective fuses, this still isn't a major problem as long as the alternator can keep up. If the alternator can't keep up, you'd know as system voltage would drop low.

This has me wondering where are you taking your voltage reading? If measured near the front of the car, say at the cigarette lighter like some idiot suggested :icon_redface: , you may not be seeing the true picture of what the battery way in back is getting.

If my TheoryDuJour™ holds water, maybe there's a difference between the alternator output and what the battery actually receives. Thus my question about where you're taking the voltage reading, especially while driving. If your meter has a min/max recording feature, try setting it up directly on the battery posts. Turn on the meter after starting the engine (so you aren't recording the normal dip in voltage under the load of the starter), turn on the min/max recording, and duplicate your typical morning drive as much as possible, with maximum electric load: Headlights on, heater running, seat heaters set to stun, defroster on, stereo blaring ABBA, you know, your typical drive.

At your destination, shut down the engine quickly and then see what minimum value was recorded during the drive. I'm willing to bet your reputation you will see substantially lower than the 13.5V you'd normally see at the alternator.

If your meter doesn't have a min/max feature, you could rig up some long test leads, fold down part of the back seat, and put the meter near the driver's seat so you can monitor it during your drive. If you get into an accident while watching the meter, I deny ever suggesting this ridiculous idea and will deny it in court.

I forgot to mention two things:

Some of my assumptions (Danger! Danger!) are based on the faults NOT being present during the morning drive immediately after the battery had been on a charger all night. The next start is hit or miss, as it's possible the battery ran down somewhat during the previous drive. Does this accurately describe your situation?

Another important question: During all of this, has the starter system cranked the engine at normal speed, or have there been any instances of slow cranking? This could point to a battery that is not fully charged, or a problem with the cables, etc.

Ken, I see you had already answered one of my questions about where you're taking the voltage readings.

I think it would really help if you can switch gears and get a reading directly at the battery while driving. This will help rule out faults that only occur in motion or are related to your typical drive cycle.

Yes, this is accurate :) . So far, since I've been charging the battery overnight, I've had no EPB faults on startup, but it's pretty reliable that I see the EPB fault on the next start up after my 34mi drive with all the electrical gubbins running.

Never once has there been a sluggish start. Always fires right up.

Ken

I'm going to rig up a long test lead tonight and try to get readings in-situ during the drive tomorrow. Maybe even later today, if I have any errands to run (since I'm working from home today).

*Since I'm working from home today*, AND I received treasures from Amazon this morning (my new battery analyzer and amp clamp), I've done some data collection. Uploading a video to Youtube now. I'll post a reference to it and some highlights when it's ready.

Ken

First, the videos:
Highlights:

Engine Running, High-beams, windshield wipers, HVAC on, Fan High, Radio Blasting, both seat heaters: 57-60A

As I turned off things, I took readings. Each component's draw is just the difference between the last two readings.

Radio: 3A
Seat Heaters: 11A
Climate Control: 16A
High Beams: 10A
Headlights: 5A
Wipers: Negligible

Not measured: radar detector, OBD scanner, Bluetooth receiver/FM transmitter for phone audio - all should be pretty negligible.

Voltage Reading at Battery under all this load: 13.8v

I ran the battery analyzer before what you see in the video, and the result is in the attached image.

I don't see anything out of the ordinary here. The battery seems to be performing OK. Alternator is holding 13.8v under a nearly 60A load, which seems a low. I would appreciate something like 14-14.5v under that kind of load.


https://cimg7.ibsrv.net/gimg/www.jag...e5e4190f31.jpg

Static battery CCA test

https://cimg6.ibsrv.net/gimg/www.jag...debeb99504.jpg

Starting test

https://cimg5.ibsrv.net/gimg/www.jag...c458c5d0a7.jpg

Charging test

Those above look OK. Not particularly helpful but OK.

Hooked up jumper wire from the battery to the cabin this morning. Battery was on charger, indicated it was in float mode this morning.

After disconnecting the charger, hooking up the jumper wire (trunk open, various doors open, etc.), battery voltage indicated: 12.55v

Starter running: 11.4v
Charging Volts : 14.5v
After - 15 min : 14.15v
34 min : 13.9v
41 min : 13.85v
46 min : 13.7v
Arrived, key off: 13.2v
48 min : 12.97v
49 min : 12.78v
50 min : 12.64v
51 min : 12.55v
52 min : 12.54v
Door open . : 12.46v
Exiting car : 12.49v

At the 46-47 minute mark, I arrived at work and parked. I took the key out and just monitored voltage for the next 5 minutes.

So, charging voltage looks "ok", battery test says "ok", but those resting voltages under a pretty small load (I measured it yesterday as starting at 4A, then dropping to 1.5A, then 800mA after the trunk light fuse was pulled.

What's going on here?

Ken

Nothing that tells you much.

Back to measuring after it should have shut off / volts after not being on a charger overnight etc i.e. the usual stuff.

Alright, making some progress. I've been trying to define exactly when the problem occurs, so we know how to attack it.

I asked about any sluggish starts, as the charging and starting systems share the same heavy cable between the front and back. If you had a problem in that heavy cable run, I think you'd also see sluggish starts.

What happens if all was good directly off the charger, you drive to work with your typical electrical load and no faults, but then instead of letting the car sit all day, you try a restart within a few minutes, such as if knocking over a liquor store? Does the car need to sit at least several hours without the charger before the fault returns, or does the length of time since the last shut down not have any effect?

Thank you for humoring me and setting up long test leads to the battery. I was testing a couple of longshot theories and neither held any water:

1) A fault in the long, heavy cable run between the front and rear of the car. Your battery is seeing good charging numbers from the alternator. The 2003+ cars have a "smart" charging system that start out around 14.5v and taper down to about 13.5v. Your charging values look spot on.

2) A slippage problem with the serpentine belt driving the alternator. If the power steering or water pump, for example, had too much resistance, the belt could have been slipping at the crankshaft pulley, dragging down the alternator, too. There's no evidence of that with the good charging values you're seeing.

I'm in full agreement with Jag V8 that it's time to run the full quiescent drain test. The last I saw this mentioned was in post #27, at 60mA, which is too high. I wonder if you've got an individual module that is intermittently not going into sleep mode, and the current drain could be much higher if you could only catch it. Have you rerun this test yet? You've got that fancy new clamp-on ammeter calling your name. Does it have a recording feature?

I remember one thread where the drain was caused by a module (power seat control?) periodically powering up for a few minutes and then going back to sleep. With a non-recording meter, you'd never see it unless you happened to be staring at the screen exactly when it happened.

Okay, you wore me out. I got dizzy and out of breath just watching you run back and forth between the trunk and the driver's seat.

13.8V under a heavy load is excellent performance from the charging system. Please see the previous comments about the smart charging system on 2003+ cars. It will start out around 14.5V as needed when first started, and then settle down around 13.5V after a few minutes. No charging problems indicated there.

The results from the battery analyzer? Keep in mind the marketing department at Foxwell probably insisted the display would show the text "Good Battery" instead of the more accurate "No Glaringly Obvious Faults Present at This Exact Moment". I have a similar analyzer, and like any test equipment, the results aren't always 100% conclusive. There are limitations to virtually any test you can run, so always be skeptical.

Can you please refresh our memory about why this battery was replaced? About a year ago, wasn't it? Were you ever getting the parking brake fault before this battery was installed? I've got to admit I've not been very impressed with Autozone's WillItLast house brand. If you rerun the quiescent drain test, and all is within limits now, the next thing to suspect is the present battery. Since the parking brake faults behaves itself when the car comes straight off the battery charger, I don't thing we're looking at anything besides a low voltage situation.

Yeah, I'm skeptical of the battery at this moment and here's why:

When I got back to the car after work, it had been sitting for almost exactly 8 hours. The voltage reading? 12.19v - basically nearly "dead". It started RIGHT up, like there was no problem whatsoever.

I replaced the battery on Oct 6, 2016. I was getting a bunch of sensor gremlins, and it was reading 12.24v. Here is the thread on that fiasco: https://www.jaguarforums.com/forum/s...er-run-170428/

This feels like a repeat of that episode. I'm pissed that the battery "checks out", but the Jag hates it. How do I convince AutoZone to warranty the thing? I don't even really want to, to be honest - the hassle of this for the past few months makes me want to get a battery that JUST WORKS...

Thanks for all your help - it's amazing to have the support of my fellow Jag-lovers out there :)

Ken

Oh, and to answer your question about getting the EPB fault before this battery? No. I never got it before last winter, AFTER I got this gem of a battery.

:(

Ken

I've had the liquor store robbery pattern many times :) The most recent was the valet incident. Drove into town, and all was well. Valet started the car and the EPB faulted. It's done it to me at the gas station, the grocery store, the Pharnacy, the cannabis store... Hey, it's legal here ;)

I'm putting a new battery in tomorrow.

There's a big problem for it to be so low.

Yep, that's why people are fooled.

You look to have a dead battery or a drain. Maybe both (the latter causing the former).

I'd HIGHLY suggest trying a different brand battery. I've had excellent results with NAPA premium or DieHard brands. The WillItLast warranty? You may be SOL there, as they're probably just going to give you another battery, if they'll even agree to that.

Diagnosing a bad battery can be tricky in a situation like this. It's usually not a slam dunk, but more a Hail Mary after a careful process of elimination. As JagV8 has said, with the typical pattern, the engine will start just fine even when the battery is low, so it doesn't seem to make any sense to blame the battery for a fault light, but forum experience has shown otherwise.

Re: The liquor store robbery pattern - You'd have to have a HUGE drain for behavior like that, IF (big IF) the charging system was up to snuff. In theory, if you left your headlights on, that's also a huge drain, but shouldn't cause a significant problem if left on only for a few minutes while you emptied the cash drawer. The other possibility is an intermittent problem with the charging system so the battery was already run down from driving. The only thing I could recommend there is to monitor the charging system while driving for a few days (not literally nonstop driving for a few days, unless you're really up for the challenge and have saved some empty Gatorade bottles).

So, um, are you going to update that old thread with the fix, or do we have to publicly shame you?: :icon_mrgreen:

tomnewbatteryorrow


Is that what you had in mind? Been waiting on pins and needles all day, then I realized I may have misunderstood you.

Well, it became the "crank-no-start" thread I started shortly after my last update, but - since I don't want to earn your ire - I'll update that thread :)