M6 Won't Start After 2 Days of Not Driving

[bigbrian]

I am having a problem and looking to find out if others have the same problem.

If I don't drive my car for 2 days on the 3rd day my car won't start. Everything else powers up but the starter will not spin up. All I have to do is place a small 4amp charger on it and then it starts right up. It almost seems like it's not a low battery issue but something else because putting a small 4amp charger on the battery for 15 seconds and the car starting doesn't do anything at all in terms of charging up the battery.

I just put in a new Exide EDGE AGM battery 2 weeks ago because my previous battery was causing audio problems with my aftermarket JL Audio amplifier. I was hoping this would fix the issue of my car not starting after 2 days but apparently that isn't the case because it happened again today.

I've talked with BMW about this and of course they blame my aftermarket amplifier but there isn't anything special about the amp. It turns off when the lead wire shows no power to it so I am not sure how this is draining the battery.

Anyone else have this issue? I cannot believe I own a $120k car that has to be jump started after 2 days of not driving it.

Brian

[devondragon]

FWIW mine has sat for 10-11 days in the Boston winter cold, and started like a champ when I got home from my trip. Could you disconnect the amp and see if that changes things? Weird Sorry to hear it.

[bigbrian]

Yeah something must be causing the problem... The only aftermarket items I have connected to power are the amp and the radar and laser jammer. I called the audio shop and he is going to take a look at a few things with the aftermarket connections.

I assume he is going to turn the car off (and allow it to go to sleep) and see if there is any voltage pulling from the hot leads for the amp and radar and jammer.

It's so weird though because the amp runs on a relay, if there is voltage from the lead wire the amp powers on, once the voltage from the lead wire is not there the amp turns off. Who knows I guess.... Shrug.

Brian

[Mr.SugarSkulls]

I fly back and forth from Mexico City to LA monthly, and have my m6 in MX city, so it sits for two weeks garaged out of each month.

Starts up like a champ each time I come back.

This is also the first time I've read of this happening, so it's most likely an aftermarket product reaction. Hope it gets cleared up!

[M6-Coupe]

mine was sitting in garage for 3 weeks when I was out of country. No issue when I came back.

[devondragon]

I hope he's able to fix that for you! Hopefully it's something simple.

[adamg13]

Alot of the larger, late-model BMWs have this issue. I remember reading about it on the 6/7 series forums fairly consistently. The customer care package for the N63 engines included installing a larger capacity battery to alleviate this and some other issues. So far the bulletin hasn't extended to the S63tu engine, as far as I know, but if you push your dealer they may be able to make the change for you as well. Unless the M6 already has a larger capacity batter than the 650?

There doesn't seem to be alot of rhyme or reason as to why some owners' batteries don't hold a charge. My past two 750's would sit in my garage for weeks at a time with no issue when I returned from traveling, and I do mostly short city commutes which are supposed to be the worst when it comes to keeping the battery charged. Just left my M6 for a week with no problem either.

[adamg13]

Something to consider as well - do you store your key near your vehicle, or let your wife keep an extra key within the vicinity? I recall one owner resolving the issue after realizing the car's electronics were continuously loading up because it sensed the key and assumed an impending start.

[bigbrian]

Originally Posted by adamg13

Something to consider as well - do you store your key near your vehicle, or let your wife keep an extra key within the vicinity? I recall one owner resolving the issue after realizing the car's electronics were continuously loading up because it sensed the key and assumed an impending start.

The key sits just inside the garage door to the house and is definitely within range of unlocking/locking the car. This is an interesting piece of information you bring up for sure. Next time the car is going to sit for a few days I will make sure the key is out of range to see what happens.

Brian

[EuroKar]

The vehicle key is a valid point. It needs to be X amount of distance away.
I had a client that left his key in the garage and that was the culprit.
Besides that, as long as you registered the correct AH (amp hour) rated battery in the vehicles battery control module after replacement you should not have an issue leaving the vehicle parked for an extended amount of time.
Let us know what you end up finding out

[bigbrian]

Originally Posted by EuroKar

The vehicle key is a valid point. It needs to be X amount of distance away.
I had a client that left his key in the garage and that was the culprit.
Besides that, as long as you registered the correct AH (amp hour) rated battery in the vehicles battery control module after replacement you should not have an issue leaving the vehicle parked for an extended amount of time.
Let us know what you end up finding out

Hmmm... I didn't register anything after the battery replacement but the car is going to the dealership next week for a few things I need fixed so I will tell them to do that (as I don't have access). Thanks for the heads up on the EuroKar!

Brian

[Jay-K]

shouldn't be an issue,
must be something about the battery..

[CFM3]

I've had this problem with our X5M in the past. It is particularly an issue in the cold (head over to the X5M forum and read about it, it's pretty prevalent). Basically we would get the increased battery discharge warned frequently in colder weather (these last two winters have been less than ideal). This year, my wife came out of work to the car totally dead. We had it jumped and took it to the dealer and they replaced the battery after testing it overnight. PM me for more info but in short that resolved it.

[MaxM3F80]

Go back Vietnam over 1 month still good too...

[jvise]

I had the same issue. Keeping the key hung on the wall inside garage door seemed to be the culprit. Like to keep all my car keys together but oh well. Good luck.

[JimM6GC]

Originally Posted by bigbrian

... putting a small 4amp charger on the battery for 15 seconds and the car starting ...

Wow, Brian, that's bizarre. Since starter motors take 100+ amps to spin under load, putting a 4 amp battery charger on for 15 seconds shouldn't do squat. The next time you have a problem starting the car, turn on the headlights. If the headlights come on with full brightness, it is probably not a battery problem. If the headlights come on with full brightness, then one ordinarily would look to the starter relay. However, if the battery has enough juice to power the lights, it usually has enough juice to power the relay (which usually draws only about 10 amps). That is what makes your fact situation very strange.

I'm hoping the battery is in fact the culprit, possibly being discharged just enough that the 4 amp battery charger is enough to make a difference.

I can understand why the aftermarket equipment, or, more precisely, the installer, may be suspect. Many audio components likewise have a low-current relay that switches high current to the high-current components in the system (e.g., to the amplification stage). In a dedicated amplifier the relay usually is connected to the switched power supply, whereas the high-current components are usually connected to the unswitched power supply (i.e., to an always-hot wire). If the installer pulled a really boneheaded move like connecting the amplification stage to the switched power supply while connecting the relay to the unswitched power supply, then the sound would turn off when you shut off the car, but the relay would continue to be energized, thereby creating a parasitic draw on the battery and discharging the battery over time.

I agree that the location of the vehicle key also could be an issue, since it's presence may switch on some of the components.

Just my $0.02. I hope you let us know what the ultimate resolution to the problem is.

[doug_999]

Originally Posted by M6-Coupe

mine was sitting in garage for 3 weeks when I was out of country. No issue when I came back.

Another reason to live in California vs. Wichita

[JimM6GC]

Just a slight clarification to my post above. While I used the example of a relay, clearly all circuit components that feed off of the switched power supply input terminal would continue to be powered if the switched power supply input terminal were inadvertently connected to the unswitched power supply. While I have no idea if that really is what is causing your problem, it definitely fits the mold, so I would get it checked out.

Egos being what they are, ol' Clem the installer may never admit to screwing up, but hopefully he (or she - don't want to be sexist) can find a face-saving way to solve the problem if that indeed is what happened.

[bigbrian]

Originally Posted by CFM3

I've had this problem with our X5M in the past. It is particularly an issue in the cold (head over to the X5M forum and read about it, it's pretty prevalent). Basically we would get the increased battery discharge warned frequently in colder weather (these last two winters have been less than ideal). This year, my wife came out of work to the car totally dead. We had it jumped and took it to the dealer and they replaced the battery after testing it overnight. PM me for more info but in short that resolved it.

That is funny you mention this... We have the issue you are talking about in our X5M and it seems to happen when it's really cold. The X5M hasn't been dead but we frequently get the warning.

I am going to take the M6 to the dealer to have some tests run. The battery is brand new (purchased it a couple weeks ago) so I don't believe it's battery related at this point.

Brian

[bigbrian]

Originally Posted by JimM6GC

Wow, Brian, that's bizarre. Since starter motors take 100+ amps to spin under load, putting a 4 amp battery charger on for 15 seconds shouldn't do squat. The next time you have a problem starting the car, turn on the headlights. If the headlights come on with full brightness, it is probably not a battery problem. If the headlights come on with full brightness, then one ordinarily would look to the starter relay. However, if the battery has enough juice to power the lights, it usually has enough juice to power the relay (which usually draws only about 10 amps). That is what makes your fact situation very strange.

I'm hoping the battery is in fact the culprit, possibly being discharged just enough that the 4 amp battery charger is enough to make a difference.

I can understand why the aftermarket equipment, or, more precisely, the installer, may be suspect. Many audio components likewise have a low-current relay that switches high current to the high-current components in the system (e.g., to the amplification stage). In a dedicated amplifier the relay usually is connected to the switched power supply, whereas the high-current components are usually connected to the unswitched power supply (i.e., to an always-hot wire). If the installer pulled a really boneheaded move like connecting the amplification stage to the switched power supply while connecting the relay to the unswitched power supply, then the sound would turn off when you shut off the car, but the relay would continue to be energized, thereby creating a parasitic draw on the battery and discharging the battery over time.

I agree that the location of the vehicle key also could be an issue, since it's presence may switch on some of the components.

Just my $0.02. I hope you let us know what the ultimate resolution to the problem is.

I will definitely update the thread with the root cause once BMW and/or the installer digs into it more. I am not letting the ball drop on this problem because it's an extremely annoying problem. Hopping into your $120k car in the morning when it's 20 degrees outside to find out it won't start is the shits. lol.

Brian

[mjr24]

Brian, mine doesn't do this....and it's friggin 5 degrees here. I sometimes go a week without driving it (it's in garage but garage can't be warmer than 30-40) and it fires right up. I agree a battery replacement should fix the issue.

[Mr.SugarSkulls]

Originally Posted by doug_999

Another reason to live in California vs. Wichita

Right??