[EB89]

Originally Posted by Three_thirty_I

No JB4, and my car is 100% stock. I have been continuing to monitor the battery all this time and it really seems to be a case of an intermittent drain caused by the electronics not completely entering sleep mode. In fact, I have caught it out at least once or twice waking up, at least that's what it seemed like. The car was sitting for probably a good hour or so, and I happened to be in the garage at that moment, heard the car make noises as if I had opened a door or something to that effect. So I will still have to figure this out, but at least I know how to work around it. A mech that I spoke to mentioned the switch box on the driver's door for the windows etc as being a possible culprit. Will have to check that out.

You dont have a spare key fob dropped inside the car somewhere do you, its not something like that :/?

[Three_thirty_I]

Originally Posted by EB89

You dont have a spare key fob dropped inside the car somewhere do you, its not something like that :/?

Nope, and this car doesn't have comfort access, so even if there was a key inside somewhere (or near the car), it wouldn't matter. And besides, this seems to be quite intermittent, with the only thing that I have notice that affects it is if all the door locks are cycled from locked to unlocked when it's found to draining the battery. But this could also mean that some other module is the culprit, so I need to try to determine what is preventing the system from entering full sleep mode when this happens. We are currently in the middle of winter here and the nights are fairly cold, not crazy snow outside cold, but wet and cold, and even though the car is always living in the garage, it gets very cold in there. And yet, the battery is still able to hold up fine for a week of standing. Although, it was particular cold over this past weekend, so decided to just give it a charge anyway, it's been weeks since I let the Ctek work its magic. I will eventually figure this out, but any help or advice is always most welcome!!

[markslc1]

I'm having similar issues with an intermittent electrical draw. Ever change the window switch? Other cause? How were you testing voltage (at the battery each time or via an OBD tool?) Its hard to test voltage with all the systems active and the trunk open and drawing current.

[Three_thirty_I]

Originally Posted by markslc1

I'm having similar issues with an intermittent electrical draw. Ever change the window switch? Other cause? How were you testing voltage (at the battery each time or via an OBD tool?) Its hard to test voltage with all the systems active and the trunk open and drawing current.

Sorry, haven't been online for a while. Still haven't resolved this, been a bit busy lately. But will be taking the car to have things tested, and hopefully it can be fixed. Haven't changed the window switch yet, and that is very possibly a potential cause for all of this. I am testing voltage simply by connecting a multimeter to the jumper point in the engine bay. With the bonnet (hood) open, the car's electronics do still go into sleep mode, and I can see when this happens in various stages based on how the voltage jumps/recovers - this is also how I have been spotting when it is stuck in some sort of excessive power drain situation. I just hope that I can get this sorted out! I seem to think that there is a constant moderate amount of power drain, and then there are those rare cases where it is draining the battery a lot faster. But typically I can get away with the car standing for a week between drives or charges. But not being able to use the car as normal and just trust that it is fine to park and leave, is annoying!

Does your car have IBS, and with that, I mean, does it have the IBS negative terminal, or does it just have the normal brown ground cable like mine does? How long does your battery last before it is drained?

[cdm244@gmail.com]

these E90 battery problems are getting to be way too common - especially as we are carrying around a 54 lbs battery @ 90 amp hours running a wiring bus loaded with checks and safe guards. A few things to look for:

- within a few minutes of shutoff (shorter if doors locked) the start button LED will go out when sleep mode is entered

- normal sleep mode parasitic draw is 9 to 21 ma depending on options

- 9 - 21ma equates to about a .01 volt loss per day from a healthy battery

- but after 10 days the rough loss of .1 volt means that the battery has lost 12% of its state of charge (this is why a month in the airport parking lot could be a problem)

- to check parasitic draw; since checking at the battery means that the open trunk prevents sleep mode, use the front jump points (I have an LCI and have no hood up/down switch); take a decent extra battery and hook up as if jumping the car; wait a few hours to allow both jump and car battery to equalize at the same voltage; then just connect your amp meter between the jump battery negative and the black jumper cable: the reading you get needs to be simply doubled to indicate actual parasitic draw (two sources in parallel will share any load); hopefully you'll see a reading in the 3 to 10 ma range.

[Three_thirty_I]

And to make matters more complicated, my E90 is an early model and does not appear to have the IBS system (not all E90 models did, only the later models), and it came with a 70Ah battery, not 80Ah or 90Ah as with other later models. Then again, it doesn't have iDrive etc.

My observations since I have been monitoring this:

- within a few minutes of shutting down (doors unlocked and bonnet open) the start LED does go out, but in rare cases I have caught it come back on, as in, something has woken the system up again - you can hear the fuel pump pressurise etc.

- the sleep mode seems to take 30 minutes in my case (no integrated phone which then takes 60 minutes), and I can see the various stages of when the various systems are shutting down by the climb in voltage - obviously, a proper load test of the current drawn is the better way to measure all of this.

- it would be interesting for me to check the current draw as it is with the bonnet open, then with the car completely closed and the alarm set. But in any event, it is losing a lot more than that in a day!

- my E46 and another vehicle take turns being parked at a storage facility, and they are usually swapped every week or so, but it has happened in the extreme that as much as 3 weeks has past, and the parked vehicle has no problems starting. I wouldn't dare trust my E90 for even a week, since it has often ended up with the battery completely drained in that period of time! Very frustrating!

- well, you can fool the central locking by clicking the boot (trunk) latch into the closed position, and then connect you multimeter between the battery negative and car's negative cable, so then the load test is conducted with the car in full sleep mode. In my car's case, this was tested before this new battery was fitted, and no issues found. But I suspect we are dealing with an intermittent problem of course. Hopefully I can take it to a place that can test this more rigorously and spot the problem when it happens.

[markslc1]

Originally Posted by cdm244@gmail.com

- to check parasitic draw; since checking at the battery means that the open trunk prevents sleep mode, use the front jump points (I have an LCI and have no hood up/down switch); take a decent extra battery and hook up as if jumping the car; wait a few hours to allow both jump and car battery to equalize at the same voltage; then just connect your amp meter between the jump battery negative and the black jumper cable: the reading you get needs to be simply doubled to indicate actual parasitic draw (two sources in parallel will share any load); hopefully you'll see a reading in the 3 to 10 ma range.

Interesting. I'm going to give this a try because I have been unable to get a reading from the battery side for parasitic draw. thanks.

[markslc1]

Originally Posted by Three_thirty_I

Does your car have IBS, and with that, I mean, does it have the IBS negative terminal, or does it just have the normal brown ground cable like mine does? How long does your battery last before it is drained?

I have a 2008 128i, which I believe has IBS. right now I use a ctek charger to keep it topped up. but if i leave it 3 days without, it wont start. I can hear and see the car going to sleep but there is still a draw for sure. battery has been tested by a shop twice as good.

[Three_thirty_I]

Originally Posted by markslc1

I have a 2008 128i, which I believe has IBS. right now I use a ctek charger to keep it topped up. but if i leave it 3 days without, it wont start. I can hear and see the car going to sleep but there is still a draw for sure. battery has been tested by a shop twice as good.

Next time you are charging your car's battery with your Ctek charger and it is showing as fully charged, I would be curious to know if yours also shows a quick cycle between topping up charge and dropping off. With mine I can hear the Ctek switching on and off every min or so when the battery is fully charged with the green LED showing on the charger. When I check the voltage, it goes from 13.65 - 13.20 volts and then back up. That's a very quick drop in voltage! And if I compare to other vehicles where I have charged their batteries, this cycle usually takes upwards of about 30 minutes!

Coincidently, I took my car for a drive this evening, and it had just had the battery charged over night, so when I parked the car later after a good long drive, I saw the voltage was sitting at around 12.65, and then I saw the start LED turn off and the voltage climbed a little bit, but far from where I would have expected it, meaning, it was sitting in one of those heavier power draining instances. I was still in the garage for a while longer, and heard the car waking up again with the start LED illuminated again. I had a few things to move around in my garage, so I decided to just take the car out again while I do that. I then took the car for another slightly shorter drive straight after and the voltage eventually settled at around 12.82 volts. It seems random when it does this, but wish I could find a way to replicate it on demand.

[markslc1]

Originally Posted by markslc1

Interesting. I'm going to give this a try because I have been unable to get a reading from the battery side for parasitic draw. thanks.

I followed your instructions, hooked up a fully charged battery at the front, let it sync up with my car battery overnight and attached the meter. And the good news is that I can get a reading this way! The results

Car fully awake: 2.52



Car locked and asleep after 5 min: 0.01



So it appears the parasitic drain is well within parameters (under .50). But it seems especially low doesnt it? And if the battery voltage is dropping to the point of not starting after 3 days, and its not parasitic, then it HAS to be the battery right? trouble is, the battery has been tested twice as good.

Any further thoughts?

[cdm244@gmail.com]

Helpful photos of your meter setup, but are you reading milli amps (ma)? On your meter is the scale determined by the 2 connectors available for your black lead? Hopefully you are reading 10ma in the sleep state - any loss has to be (hopefully) the battery or possibly the IBS (has anyone ever had an IBS work as intended? - I've had a dead battery from working on the car with the doors open and the system drops right down to no start with no battery saving feature evident at all).

[Three_thirty_I]

Okay, finally an update on what was eventually found causing this intermittent battery drain issue. Well, I hope so, and so far it seems to be behaving!

As you can tell by this thread's original post date, and the one it references that I had posted before, this issue has been ongoing for a LONG time, and been extremely frustrating and tricky to diagnose. In summary, original battery, which was 8 years old, was replaced in August 2013 with a genuine BMW direct replacement battery, so same spec and it was also registered. This was done by an auto electrician that works on BMW and other brands. Interestingly, this car doesn't have the proper IBS system with the IBS negative cable, it just has the normal brown negative cable, but apparently it still does have an intelligent battery charging system of sorts, so it is still necessary to register a new battery. While the new battery was better than the old one, it didn't feel as if it was better by that much, and quite soon I was noticing that it would battle to last a week between drives and I would have to put the battery on charge with my Ctek MXS 7.0 to keep it going. I don't drive the car that much generally, but it does get a good drive at least once a week which should be enough for a healthy battery along with the occasional maintenance charge. It then happened one day after standing for a week that I could've unlock the car, the battery was completely drained, forcing me to manually unlock the car so that I could then put the battery on charge. Then barely 2 years after the battery was fitted, I took the car for a long Sunday drive, returned, parked and locked the car, the following Sunday I wanted to take the car for a drive, battery dead! Decided to take the car to the same auto electrician and have him test the car and battery. He couldn't find anything wrong with the car, but eventually found that one of the cells in the battery was dead or weak. I was luckily able to get BMW to replace the battery with a new one and had the registration done again. All was fine until 3 or so months later, battery dead after standing for a week! Since then, I've been carefully monitoring the battery with a multimeter and the bonnet constantly open when parked, so pretty annoying! It would behave for weeks and then I would catch it pulling the battery down, but the moment you open a door or do anything that wakes the car up, you then interfere with whatever is causing the drain, so trying to diagnose this is not so easy.

This has been ongoing until last month when I decided to take the car to another BMW specialist and see if they can figure it out. So, I told them to take their time and explained the full history and my observations. Along with the obvious battery drain issues I have also been battling with the electronic steering lock giving yellow errors, this is usually when the battery is low on power and during the cold winter months, typically when the steering lock does give problems, but then I got the dreaded red error! Luckily when I reinserted the key fob, it unlocked as normal.

After a few days, I got a call from the workshop, the car's battery was not able to hold load very well, which I had already suspected (a battery that has been drained is seldom happy afterwards) and that they could see all the steering lock and other errors related to the battery issues. But they also found a fault showing that the alarm angle sensor and siren battery was dead. This is a small Lithium Ion battery and from what was explained, is located somewhere behind the rear bumper on the left side, and isn't that expensive to replace. So this was replaced and I had them fit a new battery. I decided to let them fit a larger 92 Ah battery and have them code and register.

I then also decided to fit a Ctek Battery Sense so that I can now remotely check the battery from my smart phone, which is so much more convenient and practical than constantly having the bonnet open and using a multimeter. Plus I can safely lock the car without the fear of a drained battery and having to manually unlock the car. So far the battery is doing very well, first week I was driving the car almost daily on shorter trips to see how the battery was coping, and then I purposely left it for a week to see how the battery holds, and so far, it's doing very well! I compared the readings (voltage) from the last time it was driven to exactly a week later, it had lost 0.09 volts! The state of charge percentage is still something I am trying to figure out, it does seem to be somewhat relevant, but I am more focussed on the voltage reading. I bought another Ctek Battery Sense which I have fitted to another vehicle (non BMW) to compare, and if anything, that vehicle's battery looks like it is struggling, but it did have its lights or something left on earlier this year and run flat, so that probably didn't do that battery any good, but since then, never once has it shown real signs of struggling.

This is what the Ctek Battery Sense app shows:

[sameer.vij]

Unfortunately, I have been dealing with the same issues and it seems to creep up in every winter. I have gone through two batteries and one door lock and after the car running smoothly for about 4 months I am back to square one. The car starts perfectly in the morning today is the third day in a row that I had to get a boost. Has the new battery been working okay in the long run for you?