Hello there and welcome to the BMW Car Club of America.

If you are a BMW CCA member, please log in and introduce yourself in our Member Introductions section.

Battery discharge - when is the car really off ??

Discussion in 'F01/F02 (2009-present)' started by stentoni, Dec 22, 2016.

    • Member

    stentoni

    Post Count: 5
    Likes Received:1
    Hope this post won't be too long/convoluted. Bought a used 2011 750Li (F02) in late Sept. Dealer said the battery was new. Wisconsin winters can be harsh and a week ago, temps around 15 degrees, and after not driving the car 3 days due to bad weather, I drove it to visit someone 22 miles away, almost all highway driving. Started up no problem. Leaving my visit, computer screen flashed battery charge was low and I needed to drive the car more. Drove it home, let it sit in the garage an hour, started it up, and got the same message, and the screen also read it was shutting down some electronic components to preserve battery charge. Took it in to a local BMW dealer. They ran some tests and said the battery was fine and if I wasn't driving the car that often (and is not driving 3 days really enough to cause this problem ?), I should have it on a battery charger. I figure they didn't find a blown fuse, didn't report any abnormal electrical draw, so all is OK ?

    Picked up a Duracell Ultra automatic battery charger, 1.5Ah, 4-stage charger and hooked it up. Felt really stupid having to do this, as until recently, I drove Hondas, and never had to do anything like this to any of them. Battery charged fine and in driving it today, I come home, hook it up to the charger, and it took forever for the "25%" charge light to switch over to "50%" charge. I use almost none of the electronic features, maybe the radio on a good day. Otherwise, whatever electrical draw may occur is whatever the car itself is doing.

    So, I got out the owner's manual again. Looked at instructions for starting the car and turning it off. To start it, I put a foot on the brake pedal and push the start button. No problem with that. To stop, it said to put my foot on the brake pedal, have it in "P" (Park), push the start button once, and set the Parking brake. In the time I've owned the car, I've never set the parking brake. For the uninitiated, Wisconsin (like Illinois) is a relatively flat state. When I stop, I've been stopping the car by foot on the brake, putting it in park, pushing the start button to turn it off, removing my foot from the brake, and pushing the start button again with my foot off the brake, which seems to turn off the speedometer light, computer screen, and radio off. Not pushing the start button twice leads to all internal lights and computer screen remaining on for around a minute or so, which I thought could contribute to shorter battery life.

    So, I have to ask, shutting down the way I had been doing until today, was I leaving the car "on", adding to any unusual current draw ? Must the Parking brake be set at all times for the car to actually be "off" ? I turned the ignition on (no foot on brake pedal, pushed the start button once), set the Parking brake, and my battery charger was plugged in at the time. Charge shot up from 50% to 100% in a matter of seconds, which made me wonder if not setting the Parking brake meant the car was still "on".

    Any thought anyone has would be greatly appreciated. Maybe it's just me, but I find this car to be way over-engineered. I do love it, though.
    • Member

    MGarrison

    Post Count: 3,866
    Likes Received:243
    These modern bimmers are complicated - Charlson will have a better idea than I would, I wonder if something (no idea what, though) might be keeping it from going into 'sleep' mode. I would presume after some period of time it should switch to some minimum-power-consumption mode/state. Maybe check to make sure there's no programmed automatic venting set (not sure where that setting would be, somewhere in the idrive settings I imagine). I don't know the car, but, yes, I'd think a 50-75% battery-power drain overnight shouldn't be the norm.
    • Member
    • Technical Service Advisor

    charlson89

    Post Count: 2,416
    Likes Received:133
    The F02 is a complex vehicle with all the electronics in them now days. I believe the average F02 has over 100 computer in it so power consumption can be a issue. First you are correct that you need to hit the start stop button two times to shut down the vehicle and start the sleep mode. When you push the button once is basically turning the car on without the engine running. And if you only hit the button once when shutting down is the accessory mode. Yes leaving this on can draw the battery down. The parking brake is not needed to shut the vehicle down. Basically to know the vehicle has went into sleep mode is to look at the shifter and make sure the green P is off and the start stop button is no longer lit up this can take up 45 mins. If these lights don't go off then the vehicle isn't sleeping and there is problem that needs to be looked at. Of course during the colder times batteries can drain faster and start to freeze as the charge level drops. If the battery is frozen no charging can happen. The vehicle uses a sensor on the negative post of the battery that sends information on the battery to the engine module. This will monitor the battery for draws while in sleep mode and if the battery drops to low is will shut off consumers to make sure the battery can start. If the battery drops below this starting point that light your seeing will come on. This Can be read out through the BMW shop computer to see what caused the battery to draw down. The vehicle is not being used often enough or short tripped (basically driven short distances a lot) the vehicle should be put on a trickle charger once a week. But three days should not drop the battery charge that much if the vehicle is properly sleeping. I would start by making sure the vehicle goes to sleep properly and fully charge the battery in a warm place (to unfreeze if needed). Then from there monitor and see if the light comes back on.
    • Member

    stentoni

    Post Count: 5
    Likes Received:1
    Thank you for the responses to my battery query. I will start up the car and shut it down using "Charlson's" instructions to see if the green "P" light is off and start/stop button light turns off. Will then presume the car went into full sleep mode. My garage seldom gets below freezing, as the inside walls are insulated and dry-walled. Guess I'll have to wait and see what the onboard computer tells me next. Your insights are greatly appreciated. At age 67, I am a "newbie", having virtually owned and driven almost every other car there is during my time. I know that the entry and repair price of BMW is not cheap and knew that coming in, but I had no idea the battery and electrical system was so intricate and touchy. I am hoping there is no other parasitic current draw that will require greater analysis in order to fix.

Share This Page