Parasitic draw? Battery issue? Other?

Having a battery issue with my '11 128i.  I brought the car to the shop last week to have them patch a tire. They didn't do any other work to the car. The car was at the shop overnight and they patched the tire first thing in the morning. When I picked it up around 5pm, the battery was totally dead.  We jump started it and I drove home. I made sure the car was running for a good 40 minutes or so before shutting it off. Next morning...battery dead again. I pulled it out and took it to Autozone. They tested it and said it was bad. Bought a new battery and put it in. Next morning, brand new battery is dead. Charged it and ran the car for an hour. This time I went back out an hour later to see if it would start. It did, just fine. That was yesterday. This morning...dead again.

I'm new to the world of BMW ownership, only had this car a few months, and I love it. In doing some reading, I've read about having to register the battery. Mine has not been registered yet. Could that cause my issue? The battery I put in was the "best" Duralast battery available. When I drive the car and press the button to shut the engine off, the radio and nav screen are still active, even after I get out of the car. I think it's only active for a few minutes, but not 100% sure. It's been like that since I got the car and I never had a battery issue. Thoughts?

See if this helps at all:

How to methodically find the battery drain in our E46–and fit an Optima battery, too | Project BMW M3

Zap | How to easily diagnose most any automotive electrical problem

And, yes, it can be maddening. 

Registering the battery basically tells the charge-on-demand system when to do its thing; it needs to know the condition of the battery to work most efficiently. I don't suspect that's your problem here, but the first step is going to be to put a scanner on it and get the codes. There was a recall on battery cables some time ago that caused a loss of power - it's probably been done, but worth checking just to be sure.

Thanks!  I'll have to start digging I guess.  Whatever the draw is it has to be pretty significant.  I put a brand new battery in the car around 6pm and the next morning it was dead.  I charged it yesterday around 4pm.  Went out around 6pm to check on it and it started.  This morning at 8am, dead.

Do you have Comfort Access on your car? You're not leaving the key in it, are you? That can prevent the car from going to sleep, which will drain the battery in short order. Most of the drain issues I've seen with these (and the E9x cousins) are due to something keeping the car awake.

Nope, no Comfort Access...I don't think.  I've only got one key for the car, and I never leave it in.  I *think* I forced the car to fall asleep when I shut it off yesterday.  I pressed the button to turn the engine off.  As usual, radio and nav screen were still active.  I pressed the start button again and everything shut off.  I closed the car and locked it.  Dead battery.

Wait...only other clue I can think of.  When I picked the car up from the shop, the third brake light was broken.  It's the little one that runs along the trunk.  This is a shop I know and trust, and they say they have no idea what happened to it.  It almost looked like a small rock hit hit it or something.  Half of it was broken off (the lens).  I haven't replaced it yet, I have a part on order.  Could it have gotten moisture in it and caused an issue?

Could be, I suppose, but it doesn't seem especially likely. Those lights have a reputation for cracking if the trunk is closed too hard, or if Sagittarius is in the third house, or if they feel like it. Easy enough to check the fuse for a draw when the car is asleep.

I would expect to see a significant draw somewhere if the battery is going dead overnight, yes?  I'm not good at all with checking electrical stuff.  Have very little experience with a voltmeter.  I'll follow the guide posted by David.

You mentioned pushing the start button again after turning the car off.  Are you sure it was really powered off and not in an accessory mode? 

In reply to rslifkin :

Yes, I'm sure it was off.  All dash lights were out, radio off, nav screen off, etc...  I thought I had made that mistake the first time.

The way you are describing turning off the car it sounds like you may have comfort access.  Do you use they key slot in the dash when starting?  The door handles on comfort access cars are bad about preventing the car from going to sleep.

I see it more on the n55 cars than the n52 but the electric water pumps can short out & cause a big draw.  Easiest way to find that is to listen for pump noises or if the engine is not too hot open the expansion tank & see if there is coolant flow with the car off.

Thanks!  The car doesn't have comfort access, as there is no slot for the key to go in, just the old fashion fob.  I will double check to make sure I don't hear the pump running, but I'm pretty sure all was silent when I shut the car off.  I haven't had time to put a voltmeter on it yet, I hope to do that today.

If you don't have to put the key fob into a slot below the start button, you do have CA. That's a prime suspect. Make sure you don't have the key anywhere near the car when testing or you'll wake it up.

I would check the water pump by running the automatic bleeding sequence, but I'm not sure if you can do that without a BMW-specific scanner.

Ah ha.  Son has my voltmeter so I'll have to start testing tonight.  Would the comfort access itself be the problem?  I am 100% certain that the car was completely powered down when I shut it off last time.  No radio, nav screen off, dash dark, doors locked, no interior lights on.  

SKJSS (formerly Klayfish) said:

 no interior lights on.  

What about the trunk light? That turned out to be the issue on my 528 a couple years ago. Since you already know something broke the third brake light, trunk latch may now be needing some adjustment to switch off the light?

Margie

In reply to Marjorie Suddard :

Good idea.  I just checked.  No dice, sadly.  

I've got my voltmeter now, but frankly it's dark and 35 degrees outside.  It can wait until tomorrow afternoon.

Did the new battery have the same AH capacity as the one it replaced? Part of the registration is that it allows you to change that so the system knows how much to deliver to the battery. 

In reply to SKJSS (formerly Klayfish) :

CA is considered problematic because it's easier to wake the car up (or prevent it from going to sleep). I don't have it, so I'm not personally familiar with exactly how it does this, but there's a lot of information out there.

Comfort access is a cause of many draws, first the way the system works, when a key with the correct frequency is close enough to the vehicle, the car wakes up & checks if the keys is for the car. Secondly the door handle antennas have a tendency to short & cause a draw.  Usually they will stop working at this point so if one of your handles will not unlock the car, chances are you found your draw.

Problem has gone away????  I left it on the charger longer than I had previously...kinda by accident... and now it's fine.  I'm not showing a draw on the battery with my voltmeter.