F30POST
F30POST
2012-2015 BMW 3-Series and 4-Series Forum
BMW Garage BMW Meets Register Search Today's Posts Mark Forums Read
BMW 3-Series and 4-Series Forum (F30 / F32) | F30POST > Technical Forums > Mechanical Maintenance and TSBs: Break-in / Oil & Fluids / Servicing / TSBs and Service Bulletin > AGM Battery Lifespan
GetBMWParts
Post Reply
 
Thread Tools Search this Thread
      10-19-2020, 11:33 AM   #1
Pray for Mojo
Major
Canada
430
Rep
1,115
Posts

Drives: 2014 M235i & 2018 X3 M40i
Join Date: Apr 2014
Location: Calgary

iTrader: (0)

AGM Battery Lifespan

My 2014 M235i (Dec 2013 build) has a nearly 7 year old AGM Exide Battery. Anyone replaced theirs yet? Engine was long cranking cold starts a couple days this week when we got early winter. Curious how many years people are getting out of these batteries before replacement.

I haven't got the low battery warning on my dash yet, but it has shown up every winter when the temperature gets down around -25c, so it's not the best indicator for me.
Appreciate 0
      10-19-2020, 12:02 PM   #2
HighlandPete
Lieutenant General
6654
Rep
15,858
Posts

Drives: BMW F11 535i Touring
Join Date: Mar 2007
Location: Scotland, Highland Region

iTrader: (0)

Mine is entering its 10th winter. I sense it will need replacing this winter.

Covid use (or rather lack of use) hasn't helped this year. Putting it on a CTEK charger has helped, but voltage is dropping a bit too fast, from a charge, to believe the battery will cope with another winter.
Appreciate 1
      10-19-2020, 12:06 PM   #3
Billfitz
Lieutenant General
Billfitz's Avatar
United_States
8149
Rep
15,935
Posts

Drives: '15 328iX GT
Join Date: Jan 2015
Location: New Hampshire

iTrader: (0)

Mine is six years old and shows no signs of needing replacement. However, when the temperature consistently gets below freezing every night I'm fastidious about plugging in my battery maintainer. if you get a low battery warning when it's cold you should be doing the same.
Appreciate 0
      10-19-2020, 12:14 PM   #4
Pray for Mojo
Major
Canada
430
Rep
1,115
Posts

Drives: 2014 M235i & 2018 X3 M40i
Join Date: Apr 2014
Location: Calgary

iTrader: (0)

Quote:
Originally Posted by Billfitz View Post
Mine is six years old and shows no signs of needing replacement. However, when the temperature consistently gets below freezing every night I'm fastidious about plugging in my battery maintainer. if you get a low battery warning when it's cold you should be doing the same.
Mine was giving the warning last winter after sitting on the charger all night. It would start effortlessly, drive the entire way to work, but when I shut it off it would chime low. After it sat in my warm work parkade all day it would be fine for the trip home with no warning on shutdown. The system seems really sensitive to cold battery showing low voltage.
Appreciate 0
      10-19-2020, 12:40 PM   #5
Billfitz
Lieutenant General
Billfitz's Avatar
United_States
8149
Rep
15,935
Posts

Drives: '15 328iX GT
Join Date: Jan 2015
Location: New Hampshire

iTrader: (0)

One problem is that the alternator isn't as large as it could be. When driving in cold weather the heater motor draws a lot of current, while the battery doesn't charge well because it's in the coldest spot in the car. I haven't had a warning, but when it's cold after returning home from a drive my tender never reads the battery as having a full charge. It does always show it fully charged the next morning, so I chalk it up to the engineer who decided to save five pounds of weight by using a too small alternator.
Appreciate 0
      10-19-2020, 10:31 PM   #6
Polo08816
Brigadier General
1594
Rep
3,924
Posts

Drives: 2014 335i M Sport
Join Date: Sep 2010
Location: MD

iTrader: (0)

Quote:
Originally Posted by Billfitz View Post
One problem is that the alternator isn't as large as it could be. When driving in cold weather the heater motor draws a lot of current, while the battery doesn't charge well because it's in the coldest spot in the car. I haven't had a warning, but when it's cold after returning home from a drive my tender never reads the battery as having a full charge. It does always show it fully charged the next morning, so I chalk it up to the engineer who decided to save five pounds of weight by using a too small alternator.
Isn't the alternator on the N55 200amps or more? That's a pretty sizable alternator for a passenger car.
Appreciate 0
      10-19-2020, 11:03 PM   #7
Pray for Mojo
Major
Canada
430
Rep
1,115
Posts

Drives: 2014 M235i & 2018 X3 M40i
Join Date: Apr 2014
Location: Calgary

iTrader: (0)

These cars are designed to keep the battery around 80% charged, at that level the battery will live the longest.

I think what happens with my car, the battery goes from 10c at work inside to -20 or -30c overnight. When I start the car the battery is cold and shows less voltage, so the car thinks the battery is low. The temperature change is enough of a difference that 80% ideal charge looks low enough to cause the warning.

It's never given me trouble other than the warning, and I always assumed it was slightly over engineered and sensitive. Problem is I don't know when this battery will be an issue and now it's 7 years old. If others have got 10 years I think I'll wait and see if it becomes a problem.
Appreciate 0
      10-20-2020, 07:31 AM   #8
Billfitz
Lieutenant General
Billfitz's Avatar
United_States
8149
Rep
15,935
Posts

Drives: '15 328iX GT
Join Date: Jan 2015
Location: New Hampshire

iTrader: (0)

Quote:
Originally Posted by Polo08816 View Post
Isn't the alternator on the N55 200amps or more? That's a pretty sizable alternator for a passenger car.
230 amps, but at what RPM? It won't put out 230A driving around town, let alone sitting at a stop light. Then consider what's electrically powered in the car, which is pretty much everything, including the steering and water pump. Also, while 230 amps is more than enough to power a house at 110v, that's because 230 amps at 110v is 25,300 watts. At 12v 230 amps is 2760 watts. The radio alone can eat up a substantial portion of that. From an engineering standpoint it's more efficient to power as many devices as possible electrically rather than mechanically, but if you do that the alternator should be sized to give adequate output under worst case conditions, not best case.
Appreciate 0
      10-20-2020, 10:20 AM   #9
BMWILUVU
Lieutenant Colonel
809
Rep
1,597
Posts

Drives: 340ix
Join Date: Mar 2017
Location: The Boibs

iTrader: (0)

I replaced mine at 4 years and I had not used a battery tender and it was 65-75%. It may have lasted another year or two but I was not taking any chances.
Appreciate 0
      10-20-2020, 10:50 AM   #10
Polo08816
Brigadier General
1594
Rep
3,924
Posts

Drives: 2014 335i M Sport
Join Date: Sep 2010
Location: MD

iTrader: (0)

Quote:
Originally Posted by Billfitz View Post
230 amps, but at what RPM? It won't put out 230A driving around town, let alone sitting at a stop light. Then consider what's electrically powered in the car, which is pretty much everything, including the steering and water pump. Also, while 230 amps is more than enough to power a house at 110v, that's because 230 amps at 110v is 25,300 watts. At 12v 230 amps is 2760 watts. The radio alone can eat up a substantial portion of that. From an engineering standpoint it's more efficient to power as many devices as possible electrically rather than mechanically, but if you do that the alternator should be sized to give adequate output under worst case conditions, not best case.
I'm not an electrical engineer, but I don't think the current is completely linear with RPMs. I would imagine the resistance would change depending on load (demand) on the alternator to an extent.
Appreciate 0
      10-20-2020, 11:27 AM   #11
F32Fleet
Lieutenant General
F32Fleet's Avatar
United_States
3525
Rep
10,300
Posts

Drives: 2015 435i
Join Date: May 2005
Location: Southeastern US

iTrader: (0)

No. I live in a mild climate so I fully expect to get 7 yrs or more out of an AGM. Especially since I'm easy on the brakes (i.e. coasting extends the duration that the alternator recharges the battery.). Remember our vehicles are mild-hybrids.
__________________
"Drive more, worry less. "

435i, MPPK, MPE, M-Sport Line
Appreciate 0
      10-20-2020, 12:10 PM   #12
Billfitz
Lieutenant General
Billfitz's Avatar
United_States
8149
Rep
15,935
Posts

Drives: '15 328iX GT
Join Date: Jan 2015
Location: New Hampshire

iTrader: (0)

Quote:
Originally Posted by Polo08816 View Post
I'm not an electrical engineer
I am. Alternator output isn't linear with RPMs. The output relative to speed is a curve, with 50% of the rated output usually reached around 2500 RPM, and 90% of the rated output by 3500 RPM. At highway speeds an alternator will produce a lot more current than the car needs, including charging the battery. In town and idling it will still produce enough to run the car, but depending on how much stuff is being powered it might not have enough left over to charge the battery. BMW addresses this concern with power management that diverts power away from non-critical devices and to what's considered the most critical device, the battery. This can cause of lots of error codes being tossed when a battery is too far gone to take a charge. But an OK battery can cause the same problems in very cold weather, because that reduces the battery's ability to take a charge. The same battery will act very different below zero than even at 40 degrees.
Appreciate 1
exE36M3486.00
      10-20-2020, 12:46 PM   #13
Onizukachan
Great Teacher
Onizukachan's Avatar
995
Rep
1,259
Posts

Drives: 06 e91 325ix
Join Date: Aug 2015
Location: El Paso

iTrader: (0)

Garage List
2006 E91 325ix  [10.00]
2006 Mini r53 JCW  [0.00]
2005 Mini r53  [0.00]
My e46s AGM lasted almost 12 years. What finally killed it was the alternator failing and me having to drive some 25-30 minutes home on naught but the battery.
__________________
‘06 e91 manual 325ix BarriqueRot
over Terra (one of 1), Nav, Sport, L7

A few OEM+ mods:
MTech front bumper, MSport wheel & handbrake, 4AD trim, full rear shades, more to come…
Appreciate 1
      10-20-2020, 06:02 PM   #14
Eschmacher
Car Hypochondriac
Eschmacher's Avatar
United_States
331
Rep
899
Posts

Drives: 2014 335i M-Sport Estoril Blue
Join Date: Feb 2017
Location: Sterling, VA

iTrader: (0)

Garage List
2014 BMW 335i  [0.00]
Mine died earlier this summer, at 7 years old.

Indications of it needing replacement were random codes of local voltage drops. Headlight module, steering module both consistently got codes for low voltage.
__________________
Power mods: VRSF IC/Catted DP - FTP CP/BP - AFE Cat-back - BM3/XHP - Dorch S2
Handling mods: Koni yellow - Eibach prokit - Millway street - M Performance LSD - M3 brakes - EBC bluestuff
Exterior: Euro LCI tail lights - Shitty ECS CF spoiler - Chinese M performance diffuser
Interior: Bavsound stage 1 and subs - custom trunk sub by Mike1327

Last edited by Eschmacher; 10-20-2020 at 06:07 PM..
Appreciate 1
      10-21-2020, 03:31 PM   #15
Jimmert
Private First Class
No_Country
63
Rep
151
Posts

Drives: BMW 420i F36
Join Date: Aug 2018
Location: The Netherlands

iTrader: (0)

Mine’s just over 6 years now and I am getting signs of replacement. After 10 days of parking (very hot weather those days though) it was flat. And there are warnings in cars memory already about a weak battery. I was thinking to postpone replacement to next year, but today I ordered a new one, why waiting if you know that you have to do it soon. Winter is coming!

Last edited by Jimmert; 10-21-2020 at 03:36 PM..
Appreciate 0
Post 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 10:53 PM.




f30post
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