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E46 M3 (2001-2006) Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006.


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Old Fri, Jun-22-2018, 05:33:41 AM   #1
MVAM3
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Default Battery charge dying with hours

Hi all,

I've been dealing with an interesting problem lately and i'm wondering if anyone more familiar with the electrical systems in our car could help out.

Over the last few weeks I've had intermittent issues starting the car after it sits overnight, it started with the car just struggling to start and progressed so that now if it sits for more than an hour, it just tries to start then the starter just clicks. Obviously this points to 3 more common issues, alternator, battery or parasitic drain.

The alternator is new and produces 14.3V even while underdriven. the battery is about a year old and gives 12.4V immediately after driving, but that voltage drops to about 11.5V within an hour (perhaps the battery can't hold a charge?). Lastly the parasitic draw test shows that the battery draw is about 10Ma while the car is in sleep mode, so i assume there is no significant draw.

To me, everything points towards the battery, which i plan to get load tested ASAP, but if anyone has any other ideas, i'd appreciate any help.

The battery is a red top Optima -35, is there any known issues with these?

Thank you all!
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Old Fri, Jun-22-2018, 06:52:49 AM   #2
johndoe
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Default Re: Battery charge dying with hours

I'd say replace your battery sir..
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Old Fri, Jun-22-2018, 07:20:14 AM   #3
mrgizmo04
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Default Re: Battery charge dying with hours

Quote:
Originally Posted by johndoe View Post
I'd say replace your battery sir..
+1

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'85 528e 164k miles (sold)
'05 M3 6MT coupe

All DIY: 330 ZHP steering rack, diffsonline 4.1 diff with rem polish, E60 short shifter lever, AKG black diff bushings/subframe bushings, Rogue rtab, WPC rod bearings, Beyer driveshaft, full SS (SS stepped V1, catted S1, resonated S2, SS sport), Sachs clutch/flywheel, rear main, VANOS bullet proofing with anti-rattle, valve adjustment, cooling refresh, Ohlins R&T/Swift 448f 672r/GC street tops and camber plates, AFD E85 Proflex kit.

Happy to help with VANOS or any other DIY job around NorCal
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Old Fri, Jun-22-2018, 09:01:58 AM   #4
MVAM3
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Default Re: Battery charge dying with hours

Thanks guys, sounds like that might be the case.
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Old Sat, Jun-23-2018, 02:29:29 AM   #5
RedM3/4
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Default Re: Battery charge dying with hours

You definitely shouldn't see the battery drop under 12v in a day. A week maybe, a day, at 10ma, it's bad.

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Old Thu, Jun-28-2018, 03:42:46 AM   #6
MVAM3
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Default Re: Battery charge dying with hours

Thanks everyone. Got a new battery and everything seems to be working perfectly.
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Discussing Battery charge dying with hours in the E46 M3 (2001-2006) Forum - Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006. at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)