I had a flat battery for the 2nd time in some weeks.
Battery is just a year old, and car is always in warm garage, never below 15C and never above 25C.

Before going out to see if someone can do a load test (I don't think they do that here), I had my multi meter out, and checked the amperage at the various stages of sleeping.

I can see the car goes into a sleep mode after some 30 minutes, but I am not sure if this is the final stage, or if there is still a module active.
Anyway, I measured 40mA after this 1/2 hr, which is acceptable according general rules, but a tat too much according Jaguar's own instructions (<30mA).

I wonder if any of you guys know your actual sleeping current?

PS. I ran out of time, but pulled the mayor fuses and disconnected aftermarket accessories, and all that did not make a difference.

Thanks.

 

With excess power output, I would suspect a ground. More than likely the one coming off the battery. Another suspect would be the beginning of cable corrosion. Does your car sit for more than 3-4 days?

 

Should a ground not result into higher readings?
The 40mA is higher than recommended, but also not a whole lot higher.
Or do I say something stupid here? Electrics are not my best friend.

 

I was taught in automotive school (albeit 25 years ago) that 50 ma ( .050 ) and under is acceptable. And to answer your question Eric, a bad ground wouldn't raise that draw test number. It's all about power consumption that would raise that number. However, let's just say the ground wire is corroded where it meets the battery terminal... during engine cranking if a ground (same rule applies for positive cable as well) wire is corroded/loose, that terminal will heat up during cranking because the starter needs all the power it can get and in turn it will need even more current which in turns out more amperage is administered pushing a healthy battery to it's limit and sometimes beyond.

To answer the OP's concern, if the current draw is acceptable (.040 or 40 ma) in my opinion the battery is highly suspect even being just a year old. This is taking in consideration that both major ground wires (at the battery and on the RH side of the engine) are in good shape. Even if the grounds are corroded, it wouldn't cause a dead battery. But it's always a good idea to keep an eye on them from time to time.

 

Yes, I also have this 50mA in my mind, although Jaguar specifies <30mA if no optional equipment is installed.
Hence my question if any of you actually measured your sleeping current.

I checked all grounds 'rear to front' some 3 months ago, but they all looked perfect and even shiny.
Made me again wonder that this car is like new, albeit almost 20 years.
Cleaned them up nevertheless.
I also have NO problems starting the engine, other then when the battery goes flat.

Maybe I should buy a battery tender and haul the battery up from time to time, just to be able to recharge to a full 100%.

Thanks anyway, appreciated as always!

 

Eric it might be a long shot but have you checked the false bulkhead. My xj8 acted similarly. I thought it was the battery also. It was badly melted when I checked it.

 

Thanks for the advice, but not melted, perfectly clean.
I will spend some more time pulling fuses this afternoon to see where the 40mA goes.
Not easy though, I have no idea how to get to the heelboard ones without waking up the modules

 

I left my theory short, but I didn't want to get too detailed until we had more info. If a battery gets overcharged somehow and the ground isn't properly isolated, the excess power has to go somewhere and bleeds off. The result of an overcharged battery will be excess heat, a somewhat warm casing and expansion of the casing from that.....this also can create terminal corrosion.
Eric, do you have an OBD scanner connected to your port constantly? If so, that can create excess draw. A batter tender isn't a bad idea, its cheap maintenance.

 

Ok, let it coming ...

Charge voltage is 14.5~14.9V on the OBD2, I measured some 14.3V at the battery at idle (that was after re-charge the battery on a tender).
I have no any indication of over-charging of the battery, and the OBD2 scanner is removed from the car since diagnosing.

Anyway, in my understanding the scanner port is on a powered supply, and switches off when the key is removed.
The Bluetooth signal disappears when I remove the key.

I ran out of time last night, but did a little experiment overnight.
I have the 1 year old battery back in the car, charged at some 12.65V, but not connected to the car.
It did not loose anything overnight.

I also had my backup battery (motorbike size) connected to the car.
Although smaller in capacity, it is for sure in good condition, and keeps voltage forever if not used.

I left the car overnight locked (and presumably sleeping).
I had 12.48V last night, but it dropped to 11.88V some 14 hours later.

So before I write down my (probably wrong) thoughts, what you think?

 

This is off the wall, but an issue I had. My glove box wasn't properly adjusted when I first got it and the light was staying on.
....btw, those are some strong charging numbers (but not out of bounds), what is the voltage just after shut down at the battery?

 

I checked trunk light and glove box light with my phone, they go out on closing.

I think those charging numbers are just as they have to be, right?
Got the same range on our SLK, and remember also from other cars.

Battery reads above 12.6V after shut down, but I will need a good ride to confirm the exact reading and its drop over time.
Probably this weekend.

 

If the 40mA is repeatable then it's fine - but the battery should not be at 11.88V so quickly. Either the 40mA went a lot higher or the battery is bad.

The 12.48 isn't that good, so I guess either not fully charged or is indeed bad.

 

Of the little I do know about car maintenance, I know the least about electrics. However, some of the best advice I have gotten from this forum is to hook-up my battery tender at home whenever I get the chance. My '99 XJ8 had gremlins that were spawning demons until I did this, and it works better than an exorcism! I was unable to determine the age of the battery, but had it tested, and it showed 785 CCA. With experimentation, I found that battery loses about half of its charge over a week without tending or driving, according to the admittedly crude meter on the tender. This is my first Jag, but I understand the battery to be the Achilles heel of these great cars. Anyway, the tending works well for me, and is not much trouble once you get used to the routine.

 

Well, as mentioned, that was on the small motorbike size battery, and that one was already a bit down from testing.

What interests me is the drop in 14 hours, against no drop of the real battery, the one which went flat before.
Seems I got a drain, I just don't understand why I read only 40mA.

One question: Is it OK to leave the multi-meter connected all night, just to see tomorrow morning what the 'sleeping' current does overnight?

 

30ma is the spec and 40 is a small draw. I usuually would see 20-25ma when sleeping. Yes ok to leave dvom hooked up. The fact that it is pulling down 2 different batteries is a good indicator also. One i would suspect because when you run them flat you kill 50% reserve cap.. Make sure you do not have a case draw from dirty batteries. Run the positive dvom on the case with neg on batt to see if you have voltage readings. You should not. I have seen everything from a couple volts to full voltage going to ground discharging batteries. Also keep in mind that once a battery goes down into the 11's(somewhere) the car can wake up and run the battery all the way down at that point. Battery tenders are cheap compared to a new battery. I have 4 tenders

 

Thanks Brutal, I did not even know you were still around, but bumped into some older threads of you while doing my forum research .
You have been a great help when I was doing my Double Fives, and above is spot on as well, I will do some more checking in the weekend with a full battery.

I did not have this problem till a year ago, so will need to do some reverse engineering on my own fabrications first.
I doubt it is the battery at this point.

 

I am starting to pull fuses and relay's, first on all aftermarket stuff like HID's.
So far no results, and I run out of time this morning, very time consuming.

Just to be sure I don't make an interpretation error (told you, I lack on electrics), this reading is as low as it goes, it alternates between a 0.03 and a 0.04 reading, while the meter set at 20mA.



Changing the red prob from left (started with 10A) to right does not change the reading.

Tell me I do it right please .

 

I just remembered this. Make sure that little door on your ignition switch is closing. That little sob could be intermittently causing your amperage draw by not allowing your modules not going into sleep mode.

 

Thanks for the heads-up, but that was the first thing I checked after reading a multitude of threads on this issue. Seems to work fine.

 

Eric are you double pressing the fob when locking the car?