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Discussion Starter · #1 ·
Tried to start this morning - got one starter clunk. Voltage was 10.2. It's on a charger now. Same thing happened about a month ago except I raised the back hatch and it had no juice to close. After charging it was fine. I have a voltage monitor in the lighter and it's been perfectly normal. The battery is about a year old.

Any ideas where to start? I'm thinking of having the battery tested. The car is supposed to be smart enough to cut the battery if it gets low enough that it might not start the car.
I'm confused.
 

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What sort of daily mileage do you drive the car? Did the car sit for an extended period of time? Even with IBS, the batteries only last around 3 years and that's when you drive them daily for at least an hour continuously.
 

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2008 535xi wagon
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Often, you'll see people point the finger at the battery. While it may be a result, it is rarely the root cause.

You have battery drain. These cars will typically shut off consumers automatically to preserve a minimum charge for starting. If you're at 10V, your battery is likely pooched, but also, replacing it without finding the drain will result in another dead battery.

See what the IBS sensor is saying about closed-circuit current monitoring. You can at least isolate it to a branch off of a relay.

Do you have comfort access? The antennae failing will not throw an error but will get hot - you can rule this out by yanking the fuse. Hell, I never put my fuse back in. Been fine ever since.
 

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Discussion Starter · #4 ·
No comfort access. I've had this car for years and my driving may be a little more now than it used to be. No warnings about excess battery drain as when the battery died before. I'll go see what IBS info I can find. The receipt for the battery is hiding in my files somewhere so I pulled it out to read the date. I have it on a charger now.
Thanks for the tip.
 

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Discussion Starter · #6 ·
If you're not getting the battery drain warnings, and your battery drained completely, your IBS sensor might be shot.

Check the wires on it, some are pretty flimsy.
Thanks!
 

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The one missing element to the discussion above is that a battery with a shorted cell (common at end of life) can self-discharge and/or just not hold any voltage on that portion of the cell (meaning it's missing a couple volts, even without excess "external" battery drain).

My personal favorite new tool (OK, one of them...) is the clamp-on multimeter with DC current capability (using the clamp - many do AC current only with the clamp, and DC with the leads). Better are those with remote reading (so you can use an app on your phone to monitor your current, with the trunk / hatch and hood shut). Here's the one I bought (no claim that it's the best deal out there now, of course). Really a nice addition to my tool chest for under $50.
 

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Discussion Starter · #8 ·
The one missing element to the discussion above is that a battery with a shorted cell (common at end of life) can self-discharge and/or just not hold any voltage on that portion of the cell (meaning it's missing a couple volts, even without excess "external" battery drain).

My personal favorite new tool (OK, one of them...) is the clamp-on multimeter with DC current capability (using the clamp - many do AC current only with the clamp, and DC with the leads). Better are those with remote reading (so you can use an app on your phone to monitor your current, with the trunk / hatch and hood shut). Here's the one I bought (no claim that it's the best deal out there now, of course). Really a nice addition to my tool chest for under $50.
Wow - clamp-on DC current. I think I need one. By the way, after 10 minutes on my ancient 10A charger I had to move some things. The battery voltage was 12-something. 10 min won't bring a battery up that fast. My suspection is a failed or flaking cell in the battery.
 

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Discussion Starter · #10 ·
After a couple of hours on an old 10a charger it reads 13+ volts. If it was really flat it would still be charging. I'm waiting it out right now.
 

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Nuclear engineer
02/2012 X5 35d M57Y CPO 119K miles NOKIAN WR G3 30K miles
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. After charging it was fine. I have a voltage monitor in the lighter and it's been perfectly normal. I'm confused.
What do YOU think is normal voltage?

BMW E60 530xi Sedan / Wiring Diagrams and Functional Description / Power train / Engine electronics / Voltage supply / Control unit power supply / Alternator /
Alternator
[ … ]
Note!
With intelligent generator control, the alternator voltage is correspondingly more frequently in the low voltage range in order to achieve a better battery charge.

With IAC the AGM battery is charged ONLY on overrun, on trailing throttle or spin down of the alternator on its sprag clutch. ALL OTHER TIMES the alternator is only maintaining accessory loads current through the IBS at zero, no charge or discharge.

A 10 Amp battery charge has fried your AGM battery. It must never see more than 4 Amps / 14.7 VDC.

I charge my AGM battery with a CTEK 4.3 MUS battery charger weekly for about two hours (summer) and five hours (winter) equivalent to about 4 ampere-hours (summer) and 10 AH winter. AGM battery service life is closely correlated with State of Charge average, SoC avg => 1,000 cycles of full capacity discharge and recharge.
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Rectangle Slope Font Plot Material property
 

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Discussion Starter · #12 ·
It's a standard flooded cell battery. Watching the voltage as I start the car is kinda fun. It slowly ramps up to around 14v as the car runs. Remember, this is a voltmeter that is stuck in the lighter, it's off when the car is off.
 

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Nuclear engineer
02/2012 X5 35d M57Y CPO 119K miles NOKIAN WR G3 30K miles
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I believe that you should have a registered and programmed Absorbed Glass Mat battery. If you have an Intelligent Battery Sensor certainly so.

The most common curse on BMW seems to be owners hacking them.
 

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It would be good to check and make sure it's a flooded battery.
My 2006 530xi came from the factory with a flooded battery.
The one I put in last year was an AGM and I coded it as such.
 

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Discussion Starter · #15 ·
The spec for this car calls for either and I could code for either. It came with a flooded battery and that's what I replaced it with. The battery is sitting fully charged now at about 12.6v out of the car. I'll check it in the morning and reinstall it. Then I'll see what the IBS can tell me.
 

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Discussion Starter · #16 ·
A little update. The battery was on the charger all night. I put it back in the car to read codes and do diagnostics. It was 12.68v when I put it in. As I was reading codes with my scanner I got a low battery warning on the dash. The scan wasn't done so I waited. A minute later I got a second warning and most of the modules I was scanning disappeared. I think the IBS is fine but the battery is not. I still haven't located my receipt so battery date will have to do. I'm off to the battery place for a big test.
 

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Discussion Starter · #17 ·
Crap. Battery tests good. Now for some old fashioned diagnostics.
 

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Something is very odd. For a good battery to drop from nearly 12.7 volts to too low to support most modules while testing, while just doing a scan or two sound VERY unlikely. For something to be drawing that much power, it's gonna be creating a CRAZY amount of heat (or light or motion - but you'd notice those). ;-)

Did you actually check the battery voltate (at the battery terminals) when the modules were going offline? It could be a voltage drop elsewhere (in a cable, ground, etc.).
 

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Discussion Starter · #19 ·
habbyguy, I'm pretty sure there is a bad connection or bad ground somewhere. The battery read 12.6v after everything shut down.
I'd bet if I do nothing it will be fine for another month or so and then do it again. I'm retired (but might need a job for parts purchasing) so I can diagnose carefully. It's a good thing the 535 is mostly OK. It's got a turbo whine that sounds like a pipe came loose and a slight transmission drip but seems OK mostly. I want to take the wagon on a vacation next month but it has to start and it has to have cold AC. I think replacing the condensation sensor will fix the cold part.
 

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+1 on the habby's post. Measure the voltage at both the jump points in the engine compartment as well as directly on the battery terminals. Also make sure that the connections on battery are clean and secure.
 
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