Strange battery issue

[80stech]

I have both my 2004 M54 X5 and the wife's 2005 M54 X3 changed over to AGM and they have been excellent so far (I am going to say 4 or 5 years but it's probably longer.) I wasn't expecting AGM to be that much better either but thought I would give them a try
You need a commercial load tester to test one though!

[Clockwork]

I am just buying a BMW AGM this afternoon for my 4.4i.

I know it costs about double than a Sealed Lead Acid but I'll give it a chance.
I do NOT drive my X5 a lot (or any of my vehiccles, for that matter), and when I do its been short trips, so no time to slightly charge/maintain the battery when I do. Hence why the X5, when parked in its Car Home) is almost 80% of the time connected to my C-Tek charger, which is suited for a Group 49 (H8) battery values.
I've used this batt tender for 18 years now on a few different vehicles and even have a larger capacity one for my e31 (has 2 Group 93 batts) and another for the R55.
I have a new (3 years ago, which is about 8k kms ago) alternator in the X5 and this battery is also about 3 years old.
I had no parasitic drain until I installed about 5 months ago, a Wolfbox rearview mirror back-up camera system and then I noticed my batt had deep discharged about 3 times until I figured it out... but the entire 35days I was not using the X5, the mirror wasn't connected to the battery and the X5/battery was connected to the maintainer on maintenance/storage mode. I have been told numerous times now that vehicle batteries are only going to last cars for abouit 2-3 years now before anew one is required.... I hate that its true, BUT at leaset its not a huge expense.

[80stech]

I actually replaced the AGM in the E70 I bought a couple of years ago because it was cranking a bit slow and it had a no-name at least 5 year old AGM in it. I didn't know about the 80 % charge thing and I am pretty sure now it needs a starter (have it but haven't replaced it yet,) anyway the no-name AGM has been sitting on the garage floor for almost 2 years now and still has full voltage and will have smoke coming out of my 500 amp load tester without breaking a sweat!

[Clockwork]

80stech, I have my vehicles all connected to a battery tender about 80% of the time when parked at home (more, if for my e31), as when I drive, I sadly so not drive it far enough distances at high enough speed to properly allow the vehicle's charging system do its thing. you may NOT need to have your vehicles connected to the tenders as much as its all dependant on a few items (read below).

I used to live about 35 mins drive away, at highway speeds, from my office and my mech always said, when I lived that far of a drive, each way, that he had never seen a car with a healthier engine and battery... I NEVER knew whatr he meant about that until I moved into a house which is now a 7 min drive from my office and began experiencing bad battery issues and engine oil "mayo" in all 3 vehicles. then it dawned on me that since I'm only driving SLOW, SMALL distances, it affects my vehicles 2 fold.

1) My charging system is not getting to recharge a battery, so over the weeks/months, the battery voltage was slowly dropping since I wasn't connecting it to the C-Tec charger religiously, (as I used to only use it when on vacation or vehicle was in storage)
&
2) the engine oil temp was not getting up to proper heat for a long time to burn off the condensation that builds up in a engine from short trips and especially from cold exterior weather temps. So I was getting the deadly "mayo" buildup in the valve covers, oil return lines and under the oil cap (thats the dead give away sign you have an issue) - obviously that problem can't be solved with a battery tender.

So now I have to choose which vehicle I drive. 4 cyl, 8 cyl or 12 cyl based on weather temps, conditions AND distances I'm going.

BUT ultimately, when I park my vehicles (at home), I open the bonnet, connect the C_Tek charger cables to engine bay battery leads and remove the oil filler cap, to allow any heat/condensation to leave and potentially avoid "mayo" buildup.
Overkill for a lot of people, but I'm fine with this VERY QUICK procedure. Hell even when I drive my vehicles to my office (underground heated parkade), I've often removed the engine oil cap and left it on the drivers seat, so the small moist warm air can escape the engine oil system.

[Clockwork]

Originally Posted by 80stech

anyway the no-name AGM has been sitting on the garage floor for almost 2 years now and still has full voltage and will have smoke coming out of my 500 amp load tester without breaking a sweat!

I'm not sure if the batt is sitting directly on the concrete, but if so, please raise it by putting some 2x4s under it to raise it off floor, (or put on a table/bench) as cold concrete KILLS battery cells. just an FYI, if you didn't know.

[X5chemist]

AGM batteries have less internal resistance. It's why they need special chargers. AGM do better if charged once a month over daily charging when not driven. If I don't drive mine, I put a 4 amp charger on it once every 3/4 weeks.

[80stech]

@Clockwork- yes the AGM is sitting on the concrete and it would be better if it wasn't but hasn't been a problem. With a good multimeter you can actually detect the voltage across the outside of the battery especially if there is any amount of dirt/moisture film on it. The AGM is totally clean plastic so I'm pretty sure it's a lot less of a problem but I haven't measured it (Yet.) Leaving the oil cap off is a good idea and even better would be to take it off while the engine is still running. I put a wool blanket or towel over both out M54s for the winter (take the mech fan off the X5) and helps a lot.

You will be a good test for the AGM battery especially if you have been keeping track of voltages with the lead acid battery. I would track the voltage on the 7 min. trips and to see if it holds without using the maintainer.

I've been a big Delco battery fan-boy for about 40 years so that's what I bought for the AGM

I didn't know there is different chargers for AGM though ??

[Clockwork]

Originally Posted by 80stech

You will be a good test for the AGM battery especially if you have been keeping track of voltages with the lead acid battery. I would track the voltage on the 7 min. trips and to see if it holds without using the maintainer.

I always use the hidden OBC menu to track running car voltage and it shows 14.1-14.3V since the new alternator was installed 3 years ago. I do worry that if I do install the AGM and do NOT keep maintaining it every few weeks, via a tender, that this AGM may then tax the alternator too much to charge it back UP when driving and then I'm dealing with another alternator repair again...
Tho you DO have my curosity peaked about this...

[80stech]

If you have a battery voltage that makes you decide that you need to put it on the maintainer is what I was thinking ?? I wouldn't worry about the alternator, it's not the GM alternator from the early 90s "that wasn't meant to charge the battery" Plus you have a V-8 so water-cooled alternator right? Should be better yet but maybe they are not ??

[BimmerBreaker]

Originally Posted by 80stech

If you have a battery voltage that makes you decide that you need to put it on the maintainer is what I was thinking ?? I wouldn't worry about the alternator, it's not the GM alternator from the early 90s "that wasn't meant to charge the battery" Plus you have a V-8 so water-cooled alternator right? Should be better yet but maybe they are not ??

N62's do not have water cooled alternators