R50/R53 :: Hatch Talk (2002-2006) Cooper (R50) and Cooper S (R53) hatchback discussion.

R50/53 R53 battery drain, it's killing me.

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  #1  
Old 04-01-2015, 03:43 PM
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R53 battery drain, it's killing me.

This started occuring a few months ago. It began with my windows rolling down and sunroof opening when I left the car out during the day while I was at work and at night when I was at home. Apparently if you leave your ECU unplugged for long enough this happens. But my ECU isn't unplugged.

Next thing I noticed was the start was becoming weak. It stayed weak for about a month and then the battery was dead.

Obviously, the first thing I did was get a new battery.

Everything was fine until a couple of days later when that battery was dead too. So next thing to get replaced was the alternator. I replaced that and charged the battery, that charge lasted a week. Now it appears I am going to have to keep recharging the battery every week and keep my fingers crossed as I do not get stuck somewhere. So far I have parked near a down hill so that I can just roll it down the hill and pop the clutch to keep it running.

To me it doesn't seem like the charge is dying during driving (probably because of the alternator), but it seems like it is dying while it is sitting still in the parking lot. The current battery is less than a couple months old, so I don't really think it's bad. If push comes to shove I will return the battery under warranty. I just wanted to see if anyone has had similar problems with the electricals on their car.

A thought might be the effectiveness of the alternator charge because of the reduced supercharger pully. I'm 99% sure this isn't affecting the load on the alternator, but just checking haha.

The battery light has not come on at all. The power steering still works. Car runs with battery unplugged. I'm stumped. Body control module?
 

Last edited by jeffreybass0; 04-01-2015 at 03:50 PM.
  #2  
Old 04-01-2015, 04:10 PM
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If the windows were opening on their own....sounds like you have a computer issue...

A shop with a multimeter and a few simple tools can determine which circurt is still using current with the car off...several diy posts too, think "optima Jim" posted a utube vid on how to do it...
Check for the obvious first...lights left on..like in the trunk...or PS fan/motor running....
Any moisture issues in the car? Wetness often is the cause of BCM or fuse on ck failure/corrosion that can cause issues....so a leaky sunroof with a damp floor is often the root cause...
 
  #3  
Old 04-01-2015, 04:12 PM
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PS...
Changing the size of the sc pulley does not change the rpm of the alternator...
Changing the CRANK pulley WOULD.....
 
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Old 04-01-2015, 04:27 PM
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Originally Posted by ZippyNH
If the windows were opening on their own....sounds like you have a computer issue...

A shop with a multimeter and a few simple tools can determine which circurt is still using current with the car off...several diy posts too, think "optima Jim" posted a utube vid on how to do it...
Check for the obvious first...lights left on..like in the trunk...or PS fan/motor running....
Any moisture issues in the car? Wetness often is the cause of BCM or fuse on ck failure/corrosion that can cause issues....so a leaky sunroof with a damp floor is often the root cause...
No moisture in the car. Everything turns off as it is supposed to. One weird thing that I did note is when the car was running and I had my multimeter attached the voltage would go down to around 1.9 volts as if there were some sort of resistance. I am going to look for a pinched wire or a short.

Originally Posted by ZippyNH
PS...
Changing the size of the sc pulley does not change the rpm of the alternator...
Changing the CRANK pulley WOULD.....
Yeah that's what I figured. Thanks though
 
  #5  
Old 04-04-2015, 06:07 AM
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Fixed,

it was the ground connection on the engine to the frame rail. When I lifted the frame rail end of the cable crust black stuff fell out. I cleaned off the area and now I have 13.8ish volts at the battery when the car is running.
 
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