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So 3 weeks ago i had the car parked for 10 days...came back the battery died(i had left my radar detector plugged in so i assume that drain the battery:dunno:)..jumped it and drove it for a week then parked it for about a week making sure nothing was left plugged in..yesterday the battery was dead...jumped it today and drove around...so am i gonna have to disconnect the battery when i park it up again and what could be causing this drainage? the battery is around 5 months old

TIA

91 525i
 

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Had simular problem on my old car. Do you have sound system? Alarm? usually that will cause the problem. I think it's normal. If you leave the car sitting for a week, just unplug the battery :)
 

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Cory
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I have a similar issue. My battery died, even one time when I was DRIVING it. I had the alternator replaced, battery replaced, then it died shortly after that. It's now in the shop and they can't figure out what is draining the battery. They decided, NOT the aftermarket amplifier, and they tried taking out all of the fuses, to no help at all. In short, I may have to buy a second battery because it looks like the first shop messed up and didn't diagnose the problem correctly (just charged me $780). Let me know if you figure it out, I'm all ears.
 

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Yea, I had the same problem about three years ago about 6 months after I purchased the car and it was driving me crazy. So after a few days of this problem and going through the electrical diagrams I decided to pull fuse #20 and for me that solved the problem. The battery would not die. A couple of weeks later the battery would not hold a charge at all. So I purchased a new battery and the problem has not returned since. In my words I do believe that Since I killed the battery numerous times that it got to the point that it would not hold any charge at all. Pulling the fuse was not the problem after all, I just had weak battery. Hope this helps a bit.:)
 

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On another make of vehicle of my acquaintance, I have had the battery drain for no apparent reason and found the fault was a bad diode in the alternator that was shorted. It allowed leakage current to flow even with everything disconnected. I'm not exactly sure what the 'load' is under these circumstances, unless it is just energising the windings in the alternator, but a new diode pack/brush assembly cured the problem. This doesn't explain FirstE34's issue though if his (her?) alternator was replaced.
 

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Cory
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On another make of vehicle of my acquaintance, I have had the battery drain for no apparent reason and found the fault was a bad diode in the alternator that was shorted. It allowed leakage current to flow even with everything disconnected. I'm not exactly sure what the 'load' is under these circumstances, unless it is just energising the windings in the alternator, but a new diode pack/brush assembly cured the problem. This doesn't explain FirstE34's issue though if his (her?) alternator was replaced.
Yeah. That's what they originally thought the problem was caused by. First we did only the battery, it died. Then we did the alternator, it lasted a week and then died again. I'm ready to drive this thing off a cliff. And yes, I'm a guy.
 

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Just throwing out ideas here....:dunno:
There are a number of items on an E34 that are continuously powered and not switched through the ignition. The stock radio has a feed that even by-passes its own on/off switch to retain the code and memory. The On-Board Computer is also powered directly, although it doesn't illuminate until the ignition is on. Likewise the Power Lock system (including its de-ice feature) has direct power - for obvious reasons. I'm sure there are others. Normally these shouldn't be enough load to drain a battery even after long periods, but if any of these items had an internal short or something, then I suppose it is possible.
 

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hi there..a have the similar problem too...troublespots,for instance, can often be isolated by noting if other components related to that circuit are routed through the same fuse and earth connections.
-did you try "finding a short-circuit" ??? -remove the fuse and connect a 12V test light in its place.There should be no voltage present in the circuit.MOve the test ligght from side to side while watching the test light.If the bulb goes on,there is a short to earth somewhere in that area,probably where the insulation has been rubbes through.
--you can try also this-turn the ignition off and connect a 12Volt test light between the battery negative post and the disconnected negative cable clamp.If the test light comes on ther is a short in the electrical system of the vehicle
--notify ma about result
 

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If the Battery & Alternator are fine then as Uskoplje said, its time to get a circuit tester or meter and see if you can trace the voltage drain.
 
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