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7 Series - E65 / E66 (2002 - 2008)
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  #1  
Old 11-29-2012, 01:31 PM
Calin Calin is offline
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Mein Auto: 2004 BMW 745Li
Exclamation alternator problem 2004 745LI

I have this car since at liest 4+ yeas, went through 4 bateries already, the last one from Dealer but did not last more then a year and that with me feeding the car electricity at liest 3 x a week. One has to realy love this car to put up with it... but I gues, I mostly love it...Lately after I got my 5th battery ( this one 50ccA bigger is a 950 just to have no isues with memory of charge setup requiring registring the battery) I descovered something that made me raise an eyebrow: I placed a Volt reader in my cigaret socket and noted that for the first 8 minutes after start there is no charge comming from the alternator!? Then suddenly I see the alternator kiking in and all goes normal. At very begining I get a red battery picture , then Generatior Failure alert for 5 seconds then nothing. In short: delayed activation of the generator but not voltage dependent (I had it on a charger to keep it from killing the new batery as otherwise the voltage goes down to 11.8 or below ove those 8 minutes, and the same thing precisely repeated at 8 minutes. A mechanic told me to change the Intrgrated Suply Module, I done it and same thing is hapening with the new one. Can I activate the Alternator manualy to bypass the dead time since it apears logical that this is the reason why the bateries are not lasting, after all this is no marine batery...or should I get one? I also noticed that once the alternator starts charging it will continue to do it from the very begining of each restarting of the car that fallows unless the car is alow to go into its hybernation phase(over night) Someone, please tell me what is this and what to do about it. By the way I got a code reader that said: No trouble code found Any sugestion? I only drive 15 to 20 minutes on most days but please do not tell me that this is the problem. My other cars all activate their alternator and I see it charging the moment the engine turns. Help!
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  #2  
Old 11-29-2012, 01:41 PM
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DFEL750I DFEL750I is offline
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In this car the alternator does not charge the battery all the time like other cars. The alternator kicks in and out....it is supposed to lengthen the life of the battery. If I were you I would look at something else as the cause of your issue.

Maybe you have a power drain on the battery somewhere or the alternator is potentially putting out too much voltage. The AGM type battery in our cars are very sensitive to over voltage. If you alternator is putting out more than 14 volts you will have problems with the battery
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  #3  
Old 11-29-2012, 01:55 PM
BuiltnBoostedZ BuiltnBoostedZ is offline
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Mein Auto: X3 xDrive35i & 350Z TT
My car does this every once in a while. I thought my alternator was on its way out. I do get alternator codes when I plug in the OBDII reader...so I would assume the alternator is in fact, going out.
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  #4  
Old 11-29-2012, 03:08 PM
Calin Calin is offline
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I read and am sory to tell you that I do not buy this. There Is no reason what so ever for any sYstem not to deliver pover when is neaded the most: right after you drained considerable power by starting. Any system with a different philosophy would be a suicidal system and would do exactelly the oposite of conserving the batery life. I am looking for a different kind of answer: a logica one and centered on the specifics of my problem. By the way, a 2004 745Li does not use a gas matt battery but a conventional lead batery, that is what I found in it when I bought it and that is what I got from the dealer when I had them installing in it last year with no success. Remember the 8 min of no charging right after start...That is the QUESTION.
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  #5  
Old 11-29-2012, 03:18 PM
BuiltnBoostedZ BuiltnBoostedZ is offline
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Then your battery was replaced...they come with an AGM battery. I replaced mine a few months ago. And if your alternator isn't charging for 8 minutes, I'd say your alternator is on its way out too.
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  #6  
Old 11-29-2012, 04:47 PM
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wjjklj wjjklj is offline
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I have a 2004 model and it definitely came with a factory AGM battery. These cars have major electrical demands and should have a AGM (Absorbant Glass Mat) battery as the replacement.

I have a couple of things that you can try that I will sell you cheap. I am a honest contributing member here and had a low voltage issue that I tried to solve by replacing items. My problem turned out to be a bad alternator.

I have a brand new voltage regulator which you could change out on your alternator. I have a used power module from my car. I bought a new one for about $500 and this was not my issue. I also have a used integrated supply module. PM me if you are interested. I will make you a deal you can't get anywhere.
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  #7  
Old 11-29-2012, 05:30 PM
Calin Calin is offline
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Quote:
Originally Posted by BuiltnBoostedZ View Post
Then your battery was replaced...they come with an AGM battery. I replaced mine a few months ago. And if your alternator isn't charging for 8 minutes, I'd say your alternator is on its way out too.
If the battery is to be considered then I would rather opt for a deep-cycle one since these cars are not in any higher cranking Amp needs then similar vehicles (not a Diesel),but definitelly being power guzlers with all the consumers and their prolonged drain would take a gas mat battery sooner out of its confort zone. About the "generator being on his way out" I thought of that myself but does not appear logical since it only does come late once after hybernating and thereafter kics in every time right as I start the car. It takes at liest 3 to 4 hours of car inactivity for the cycle to repeat again. With other words if I am out driving it all day will only do it once(those 8 minutes of no pover from generator after starting). It must be whatever activate my Alternator that decides not to activate it for those 8 minutes at the first start of the day. Any ideas how to activate the Alternator of this car manually?
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  #8  
Old 01-07-2013, 06:47 PM
JNMNL52 JNMNL52 is offline
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I am experiencing the identical problem on my E53 for the past three weeks. I thought if may be attributed to colder weather but not sure now. Was about 32 degrees for a few days, but today was 42 degrees. Still had the problem. Alternator does not charge during the first start of the day. I timed it today and it kicked in exactly at 8 minutes. It will charge at 14v the rest of the day no problem. Next day first start same scenario. I thought it may be a connection that engages once warmed up. Read on the internet of a similar problem whcih turned out to be a lazy diode in the regulator. I was wondering if there were any relays or ECU's between the alternator assembly and battery that may be failing or is it directly wired?
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  #9  
Old 01-07-2013, 07:00 PM
Davidf Davidf is offline
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Similar experience with my '04 545i. Rectifier on alternator turned out to be bad. Alternator would fluctuate from output to no output before sometimes settling down to proper operation.

Last edited by Davidf; 01-08-2013 at 06:25 AM.
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  #10  
Old 01-07-2013, 07:15 PM
JNMNL52 JNMNL52 is offline
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Quote:
Originally Posted by Davidf View Post
Similar experience with my '04 545i. Rectifier on alternator turned to be bad. Alternator would fluctuate from output to no output before sometimes settling down to proper operation.
Thanks. Just seems strange this only happens during the first start of the day for about 8 minutes, then charges normally the rest of the day.
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