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      02-13-2020, 10:52 AM   #1
heatmizr
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Charging: How many volts is TOO many volts?

Couple questions:
The charging voltage is mentioned in several threads but not the aspect I am looking for...


(1) Is the charging voltage I am reading with my plug-in monitor at the cigarette lighter accurate?
- It has seemed to be what I expected until recently - fluctuating between 11v at startup to 13-14.x while driving.

BUT lately, I am noticing the monitor going blank for a few milliseconds quite frequently... and also readings up in the high 14's like 14.8 volts. Maybe the cheap little tool is crapping out...

(2) If its accurate, is 14.8 volts too high? Battery is about 3 yrs old. I recall voltages displayed in the 14's before but this is seeming a bit high.
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      02-13-2020, 11:03 AM   #2
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What kind of battery? Agm or lead?

Do you have any code readers that you can run tests on your alternator charging the battery? Did you remove the battery and test it? Try using a special battery charger like a ctek which can help restore the deep cycle and recondition the battery?

It's entirely possible your battery is bad and you definitely don't want a high discharge scenario because it could damage some modules like the frm. Or like what's happened to me before and my 335d shut if and wouldn't start at all until the battery was changed.

Also Did you register it? Specs on the battery different then stock?
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      02-13-2020, 01:12 PM   #3
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What I know -
Battery was done on goodwill at BMW dealer ~3 yrs ago so I ASSUME they registered it. I honestly don't know what kind but it would be OE since Dealer put it in.

This behavior seems to be consistent and has been going on for months with no change. I have no low battery symptoms or other indications of any issues at this time.

Can I not test the battery without removing it? At the charging post in the engine bay? That is how I monitored what seemed to be the notable low-charging situation ~4 yrs ago of the battery it had when I got the vehicle.

Thank you for your detailed reply. I have some things I need to check...
I was originally asking more because I wanted to know if it was normal for the charging system to put almost 15 volts into the system. That seems high for a 12v battery. Really if that is considered within the bounds of normal then I am not going to worry a lot.

Thanks!
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      02-13-2020, 03:01 PM   #4
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15 v is normal at the engine bay post. I just install a brand new Valeo alternator voltage regulator and im at rock steady 15.0v. On average a alternator output is above 14v to account for all other electrical use i.e coil, lights etc.
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      02-13-2020, 09:35 PM   #5
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optimal range when engine is running is 13.7 - 14.7.. and its still ok above 12..

Quote:
Originally Posted by TwinSnailz View Post
15 v is normal at the engine bay post. I just install a brand new Valeo alternator voltage regulator and im at rock steady 15.0v. On average a alternator output is above 14v to account for all other electrical use i.e coil, lights etc.
15v is high.. non of the engine parts are designed to handle 15v..
you may experiencing corrosion, starter solenoid issue or battery needs to be checked or something else.. battery acid can boil over easily with that voltage..
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      02-13-2020, 10:46 PM   #6
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If you have no symptoms I wouldn't try to fix it.
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      02-13-2020, 11:17 PM   #7
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Quote:
Originally Posted by yco View Post
optimal range when engine is running is 13.7 - 14.7.. and its still ok above 12..



15v is high.. non of the engine parts are designed to handle 15v..
you may experiencing corrosion, starter solenoid issue or battery needs to be checked or something else.. battery acid can boil over easily with that voltage..
Oddly enough i had a remanufactor alternator that I had install for about 5k miles ago. It was producing 14.8 at first install then recently it was hovering around 13v. Getting high battery drain warning every now and then. Engine would run poorly, idles rough. Then I purchased a used oem alternator and install new bearings and new Valeo voltage regulator. I can definitely tell the engine now idles really smooth. Engine cranks and starts quicker. Before it would take 1-2 seconds of cranking, now itís like instant on lol. Maybe the battery is fully charged up.
Isnít the battery IBS unit is there to control the right amount of current to the battery and the electronics.
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      02-14-2020, 01:25 AM   #8
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Quote:
Originally Posted by TwinSnailz View Post
Oddly enough i had a remanufactor alternator that I had install for about 5k miles ago. It was producing 14.8 at first install then recently it was hovering around 13v. Getting high battery drain warning every now and then. Engine would run poorly, idles rough. Then I purchased a used oem alternator and install new bearings and new Valeo voltage regulator. I can definitely tell the engine now idles really smooth. Engine cranks and starts quicker. Before it would take 1-2 seconds of cranking, now it’s like instant on lol. Maybe the battery is fully charged up.
Isn’t the battery IBS unit is there to control the right amount of current to the battery and the electronics.
rough to smooth idle can depend on many different things.. maybe your throttle bodies needed a reset as well or battery charged up as you ve said.. its not right to connect it to 15v..

IBS works when the engine is turned off.. it checks the values at each given time and sends it to DME by BSD.. voltage regulator does the job to keep the voltage stable for you question if it was a question.. faulty IBS can confuse DME and IBS itself can cause high discharge battery by waking up DME regularly ironically.. but here is the catch im trying to tell.. when DME has no information about battery's state it it sets the alternator output around 14.2v.. thats why the optimal range is 13.7 - 14.7..
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      02-14-2020, 08:58 AM   #9
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I'm more concerned about the intermittent cutting out of the voltage display; if the charging system is actually cutting out, I assume I would be having other symptoms correct?? Or is it a separate circuit from the rest of the system?

I will put a voltmeter on it this wknd to diagnose more. As I said, it could be the cheap lighter socket monitor going faulty... It seems to go dark and come back quickly every time the voltage changes, like it will display 14.6, then cut out and quickly come back at 14.8 or whatever, until it cuts out again and comes back at yet a different voltage.

Great and Interesting info above, thanks all. Will report back after this weekend.
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      02-15-2020, 10:12 AM   #10
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I get wake up faults regarding short circuts.. 14.8 Normally on my voltage.
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      02-15-2020, 01:07 PM   #11
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You can see what your alternator/charging system voltage is (while the engine is running and you're driving around) if you unlock your cluster and run the TEST that shows the voltage. And with the engine not running but the ignition in the "ready state"...you can see what the battery's voltage is.

If you don't know how to unlock your cluster...there are multiple videos on Youtube that shows how to do it. Any BMW that is a generational cousin of your e70 X5 will use the same procedure to unlock the cluster...so if you find videos of an e60/e64/e70/e65/etc...the procedure is the same.
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      02-17-2020, 07:58 AM   #12
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I’ll just mention that for a lead acid battery 14.4v at the battery is the max you’ll typically want to charge at. There is always voltage drop in the wiring and depending on current draw. So 14.8v at the alternator is likely just fine at the battery. P.s. 14.8v is what you’d want for a lithium iron phosphate battery.

I’ll add that my two e70s needed a new alternator about every 40k miles. Heat and high loads probably shorten their lives.
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