Battery or alternator? M6

Osubucks999 · 10-02-2022, 07:38 AM

Got a message about the battery when I got in. Thought it was referring to the fob battery. I was wrong.
Came out from dinner and the car was dead.
Had it jumped….but the car wouldn’t stay running without me keeping the revs up.

It’s a 2014 M6 with only 6000 miles.

Bad battery? It’s likely been sitting for long periods of time.
Or….alternator? Seems unlikely with such low mileage.

Thoughts???

M6Roar · 10-02-2022, 07:55 AM

There is an old test to check not sure if it will 100% work on a BMW turn on the car and then disconnect the negative terminal on the better if it goes off then its your alternator. Another test to do is to get a voltmeter and check the voltage in the hood at the jumper terminals I think it should be around 14V or if you have a datalogger you can check the voltage.

I think you can do that in the secret menu too

TinCanSailor · 10-02-2022, 08:22 PM

Check the date on the battery. If over 4 years definitely a good candidate for replacement. Do you have BimmerLink, it is an easy low cost way to check the battery health. Plus if you decide to replace the battery you can update the car so the battery mgmt system charges the battery properly.

Like M6Roar said, checking the voltage while running is a great test

Osubucks999 · 10-03-2022, 08:20 AM

Thanks for the quick feedback.

JDMSteven · 10-03-2022, 10:45 AM

Absolutely positively do not disconnect your battery while it is running. These cars are far too modern to do something like that. Recipe for disaster.

Qsilver7 · 10-04-2022, 10:07 AM

Ditto above DO NOT remove the negative battery cable while the engine is running. This can damage a number of control modules.

If it was the 1960s or 1970s (when there wasn't anything close to a CPU module used in cars)...pulling the negative cable wouldn't be an issue. But as mentioned above...with all the control modules in a modern car...this could end badly doing that.

10-02-2022, 07:38 AM	#1
Osubucks999 Registered 0 Rep 2 Posts Drives: BMW M6 Join Date: Oct 2022 Location: Centerville, OH iTrader: (0)	Battery or alternator? M6 Got a message about the battery when I got in. Thought it was referring to the fob battery. I was wrong. Came out from dinner and the car was dead. Had it jumped….but the car wouldn’t stay running without me keeping the revs up. It’s a 2014 M6 with only 6000 miles. Bad battery? It’s likely been sitting for long periods of time. Or….alternator? Seems unlikely with such low mileage. Thoughts???
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10-02-2022, 07:55 AM	#2
M6Roar Second Lieutenant 86 Rep 242 Posts Drives: '14 M6GC Join Date: Apr 2018 Location: Bahrain iTrader: (0)	There is an old test to check not sure if it will 100% work on a BMW turn on the car and then disconnect the negative terminal on the better if it goes off then its your alternator. Another test to do is to get a voltmeter and check the voltage in the hood at the jumper terminals I think it should be around 14V or if you have a datalogger you can check the voltage. I think you can do that in the secret menu too Last edited by M6Roar; 10-02-2022 at 08:20 AM..
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10-02-2022, 08:22 PM	#3
TinCanSailor Fueled by Recycled Dinosaurs! 630 Rep 1,171 Posts Drives: F06 M6 Join Date: Dec 2019 Location: 813Bay, Fl iTrader: (2) Garage List 2015 BMW M6 Gran Coupe [9.75]	Check the date on the battery. If over 4 years definitely a good candidate for replacement. Do you have BimmerLink, it is an easy low cost way to check the battery health. Plus if you decide to replace the battery you can update the car so the battery mgmt system charges the battery properly. Like M6Roar said, checking the voltage while running is a great test __________________ 2015 F06 M6 Silverstone Metallic II, Individual Full Leather, B&O, Night Vis, CCB, RKAutowerks (CP Rods/Pistons, DI Cams, CF Intakes, Coated DP's & Billet Diff Brace), InfinityAuto Turbo Inlets, Mishi Oil Cooler, JB4, XHP S3, BM S3
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10-03-2022, 08:20 AM	#4
Osubucks999 Registered 0 Rep 2 Posts Drives: BMW M6 Join Date: Oct 2022 Location: Centerville, OH iTrader: (0)	Thanks for the quick feedback.
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10-03-2022, 10:45 AM	#5
JDMSteven Captain 475 Rep 742 Posts Drives: '13 F13 M6, '94 JDM Supra 5MT Join Date: May 2018 Location: Ocala, Florida iTrader: (0) Garage List 2013 BMW M6 [10.00]	Absolutely positively do not disconnect your battery while it is running. These cars are far too modern to do something like that. Recipe for disaster. __________________ 2013 F13 ///M6 Alpine White • Zandvoort Full Merino Driving Assistance Pkg • Exec Pkg • Vent Seats Vorsteiner VFF-103 Carbon Graphite 343M dimensions • H&R Lowering Springs • Soul PP Resonated Muffler Delete • AeroFunction AF-1 Carbon Front Lip • Carbon Front Grilles • Carbon Mirror Caps • IND Black Fender Vents
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10-04-2022, 10:07 AM	#6
Qsilver7 Major General 4426 Rep 7,467 Posts Drives: F06 650ix GC / F15 X5 50i Join Date: Oct 2016 Location: Indiana, USA iTrader: (0)	Ditto above DO NOT remove the negative battery cable while the engine is running. This can damage a number of control modules. If it was the 1960s or 1970s (when there wasn't anything close to a CPU module used in cars)...pulling the negative cable wouldn't be an issue. But as mentioned above...with all the control modules in a modern car...this could end badly doing that. Attached Images __________________ 2015 F06 650ix Gran Coupe`(Moonstone/Cohiba Brown)\| 2014 F15 X5 50i MSport (Space Gray/Mocha) Become a BMW CCA member! Click HERE to join and feel free to use my BMW CCA member #191509 as a referral. Last edited by Qsilver7; 10-04-2022 at 10:22 AM..
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