E90Post
 


TNT Racewerks
 
BMW 3-Series (E90 E92) Forum > BMW E90/E92/E93 3-series General Forums > General E90 Sedan / E91 Wagon / E92 Coupe / E93 Cabrio > Cold Start Voltage Drop



Reply
 
Thread Tools Search this Thread
      02-16-2020, 10:12 AM   #1
kern417
Cheapskate
4442
Rep
4,992
Posts

Drives: 2018 440i |2016 340i | 2010 X5
Join Date: Aug 2016
Location: Cincinnati

iTrader: (1)

Cold Start Voltage Drop

I have an N52 E70 X5 but posting here since it gets more traffic.

I have had an issue for a while now, where the voltage drops significantly when I start the car. Based on the readout on my radar detector, sometimes it gets down to <11.2V. It seems to be worse if I turn on the accessories 1st, then actually start the engine. I can't say that it's gotten worse with the cold weather, but I'd like to get it fixed before it messes something up and I end up stranded somewhere. I've changed the battery in the last year, and I don't think it's the alternator since the voltage ramps up to >13.5V after a few moments of initial stumbling. It also doesn't seem to happen after the engine is already warm.

Any ideas? Am I overthinking it?
__________________
Quote:
Originally Posted by umizoomi View Post
As long as 3-pedals are an option, I will exercise my right to suffer the handicap and indignity of slower shifts and reaction times.
Youtube/Instagram/TikTok: @kern417
Appreciate 0
      02-16-2020, 12:57 PM   #2
ctuna
Lieutenant General
1904
Rep
13,088
Posts

Drives: 325xi 06 wagon MT
Join Date: Jan 2010
Location: Santa Cruz, Ca

iTrader: (0)

When you replaced the battery did you get the proper size
and type.
Did you reprogram the car for the new battery type and size?
Try putting a full charge on the battery and see if the symptoms
go away.
Do you let the car sit or only drive it short distances?
Not driving enough for the battery to charge.
Appreciate 0
      02-16-2020, 02:51 PM   #3
marvinstockman
Major
399
Rep
1,073
Posts

Drives: 2011 BMW 328i
Join Date: Aug 2015
Location: Rockville, MD

iTrader: (0)

First, you don't have a problem, as 10 to 11 is the normal voltage drop when starting a car. Batteries have internal resistance, and when, say the starter draws 300 amps, a small amount of voltage is dropped across the battery itself.

Do some reading on Google before you start replacing stuff.
Appreciate 0
      02-17-2020, 06:51 AM   #4
smass
Lieutenant Colonel
393
Rep
1,578
Posts

Drives: 06 325i - 10 335i
Join Date: Sep 2010
Location: Scottsdale, AZ

iTrader: (1)

Garage List
2010 E90 335i  [0.00]
2016 F15 35i  [0.00]
2003 E53 3.0  [0.00]
2006 E90 325i  [0.00]
For my E70, the voltage drop is much greater when measuring at the cigarette lighter. If you measure at the battery with a voltmeter, the voltage drop will be close to one volt higher.
Appreciate 0
      02-18-2020, 06:18 AM   #5
kern417
Cheapskate
4442
Rep
4,992
Posts

Drives: 2018 440i |2016 340i | 2010 X5
Join Date: Aug 2016
Location: Cincinnati

iTrader: (1)

Quote:
Originally Posted by ctuna View Post
When you replaced the battery did you get the proper size
and type.
Did you reprogram the car for the new battery type and size?
Try putting a full charge on the battery and see if the symptoms
go away.
Do you let the car sit or only drive it short distances?
Not driving enough for the battery to charge.
Yes
Yes
Over the summer I do, but now that it's winter I drive it every day to work. It has plenty of time to charge.

Quote:
Originally Posted by marvinstockman View Post
First, you don't have a problem, as 10 to 11 is the normal voltage drop when starting a car. Batteries have internal resistance, and when, say the starter draws 300 amps, a small amount of voltage is dropped across the battery itself.

Do some reading on Google before you start replacing stuff.
I wouldn't think so. I don't experience the same voltage drop on any of my other cars, including my 440i. And nothing has been replaced yet, hence the question of how to diagnose the issue or what to look for. The way I see it, dropping below 11V could be dangerous, especially when our cars are so finicky to begin with. I will say it's not enough to make the lights dim or anything, but I hear the engine ramp up as it's freed up and the voltage rises. I wouldn't expect that big of a load.

Quote:
Originally Posted by smass View Post
For my E70, the voltage drop is much greater when measuring at the cigarette lighter. If you measure at the battery with a voltmeter, the voltage drop will be close to one volt higher.
I have a mirrortap connected to my radar detector. I have the same style in my 440i and it doesn't register this much of a drop. But that car I've owned since new and I take care of it. I bought my E70 with 70k and I've been fixing all the little stuff, this is just one of the last things that's bothering me.
__________________
Quote:
Originally Posted by umizoomi View Post
As long as 3-pedals are an option, I will exercise my right to suffer the handicap and indignity of slower shifts and reaction times.
Youtube/Instagram/TikTok: @kern417
Appreciate 0
      02-18-2020, 07:34 AM   #6
TunafishE93
Major
415
Rep
1,155
Posts

Drives: BMW 335i
Join Date: Dec 2019
Location: NV

iTrader: (0)

You might be comparing apple to oranges.. Most likely you are running a AGM in the E70. These are deep cycle batteries and don't behave like standard batteries..

The AGM's has a much lower "safe" voltage compared to standard, you can easily take a AGM down to 7V without damaging the battery. The AGM prefers a slower charge than a standard. The full charge voltage on AGM is higher than standard also, 12.8V vs 12.6V respectively. The 440I might have a bigger battery or standard, not sure if they a still using AGM..

Anyways I have to agree that you have no issues.
Appreciate 0
      02-18-2020, 09:19 AM   #7
kern417
Cheapskate
4442
Rep
4,992
Posts

Drives: 2018 440i |2016 340i | 2010 X5
Join Date: Aug 2016
Location: Cincinnati

iTrader: (1)

Quote:
Originally Posted by TunafishE93 View Post
You might be comparing apple to oranges.. Most likely you are running a AGM in the E70. These are deep cycle batteries and don't behave like standard batteries..

The AGM's has a much lower "safe" voltage compared to standard, you can easily take a AGM down to 7V without damaging the battery. The AGM prefers a slower charge than a standard. The full charge voltage on AGM is higher than standard also, 12.8V vs 12.6V respectively. The 440I might have a bigger battery or standard, not sure if they a still using AGM..

Anyways I have to agree that you have no issues.
Yeah it's a big boy, but I assumed it was required since it's mounted in the trunk. Alright I'll just keep an eye on things. So far only had the reverse camera malfunction, so I guess it could be worse. Just didn't want things to start shorting out one by one.
__________________
Quote:
Originally Posted by umizoomi View Post
As long as 3-pedals are an option, I will exercise my right to suffer the handicap and indignity of slower shifts and reaction times.
Youtube/Instagram/TikTok: @kern417
Appreciate 0
      02-18-2020, 05:02 PM   #8
lookalikehuuh
Major
United_States
698
Rep
1,227
Posts

Drives: 2006 330i, 2007 335i
Join Date: Sep 2014
Location: San Diego, CA

iTrader: (0)

Both of my cars do the exact same thing, takes like 5-7 seconds then the alternator kicks in and start charging the battery like normal.

BTW I have a literally brand new Alternator from FCP Euro in 1 of the cars so it appears to be just normal operation.
Appreciate 1
kern4174442.00
      02-19-2020, 06:42 AM   #9
kern417
Cheapskate
4442
Rep
4,992
Posts

Drives: 2018 440i |2016 340i | 2010 X5
Join Date: Aug 2016
Location: Cincinnati

iTrader: (1)

Thanks everybody.
__________________
Quote:
Originally Posted by umizoomi View Post
As long as 3-pedals are an option, I will exercise my right to suffer the handicap and indignity of slower shifts and reaction times.
Youtube/Instagram/TikTok: @kern417
Appreciate 0
      02-19-2020, 09:04 AM   #10
marvinstockman
Major
399
Rep
1,073
Posts

Drives: 2011 BMW 328i
Join Date: Aug 2015
Location: Rockville, MD

iTrader: (0)

Kern, what happens to battery voltage during starting has nothing to do with system voltage during normal running. Starting puts a short term very high load on you battery, and you see a short term drop in battery voltage. The alternator recharges the battery after starting. If you want to worry about something, worry about world peace.
Appreciate 0
      02-19-2020, 09:47 AM   #11
kern417
Cheapskate
4442
Rep
4,992
Posts

Drives: 2018 440i |2016 340i | 2010 X5
Join Date: Aug 2016
Location: Cincinnati

iTrader: (1)

Quote:
Originally Posted by marvinstockman View Post
Kern, what happens to battery voltage during starting has nothing to do with system voltage during normal running. Starting puts a short term very high load on you battery, and you see a short term drop in battery voltage. The alternator recharges the battery after starting. If you want to worry about something, worry about world peace.
very motivating. i'll be speaking at the next UN dinner for sure.
__________________
Quote:
Originally Posted by umizoomi View Post
As long as 3-pedals are an option, I will exercise my right to suffer the handicap and indignity of slower shifts and reaction times.
Youtube/Instagram/TikTok: @kern417
Appreciate 0
Reply

Bookmarks

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -5. The time now is 12:46 AM.




e90post
Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
1Addicts.com, BIMMERPOST.com, E90Post.com, F30Post.com, M3Post.com, ZPost.com, 5Post.com, 6Post.com, 7Post.com, XBimmers.com logo and trademark are properties of BIMMERPOST