[tom.gnade]

I just had a new AGM battery installed and got the car reprogrammed for it last Thursday, since I'd been getting low battery indicators for a few weeks. The first day, no problems. After that, on cold starts, I've been getting the indicator again. If the car is warm, usually it doesn't get thrown.

My shop said the alternator is probably bad, though I'm very surprised that would be the case at 39k miles. I'm going to try to replace just the voltage regulator first, which I've already ordered. If that doesn't work, then I suppose I'll replace the entire alternator.

Is there any test I can perform that would determine whether I should just replace the whole thing now, or is that impossible to know with just a voltmeter?

Has anyone else had a failure of the battery and alternator at such a low mileage? I'm guessing the alternator/VR could have taken the battery out with it.

[peterparker]

It could be the Battery cable sensor thing. IBS.

This senses the voltage of your battery. And if it the voltage is low, it's going to cut off power to some accessories such as the clock, comfort access, etc while your car is off.

And if the sensor is bad, it's always going to display a low battery warning. And your clock is always going to reset.

^^^ This is happening to me. For the past year I had the low battery message but my car starts up just fine. For $300, I'll get this fixed later. The only annoyance is the clock resetting, which I can live without.

https://www.fcpeuro.com/products/bmw...AaAi_IEALw_wcB

[GoRomeo]

Originally Posted by tom.gnade

I just had a new AGM battery installed and got the car reprogrammed for it last Thursday, since I'd been getting low battery indicators for a few weeks. The first day, no problems. After that, on cold starts, I've been getting the indicator again. If the car is warm, usually it doesn't get thrown.

My shop said the alternator is probably bad, though I'm very surprised that would be the case at 39k miles. I'm going to try to replace just the voltage regulator first, which I've already ordered. If that doesn't work, then I suppose I'll replace the entire alternator.

Is there any test I can perform that would determine whether I should just replace the whole thing now, or is that impossible to know with just a voltmeter?

Has anyone else had a failure of the battery and alternator at such a low mileage? I'm guessing the alternator/VR could have taken the battery out with it.

Did they register the new battery? Seems like your car is not aware of new battery installed. Therefore its the registration process on these AGM batteries.

[yupetc]

It's the alternator.

[tom.gnade]

Originally Posted by yupetc

It's the alternator.

Voltage regulator arrived in the mail. I didn't install it yet. Checked voltage on the car at rest 12.55v. Turned on the car and got the low battery indicator again. At idle with lights and blower running at max, 13.98-14.0v. At 2500 rpm, 14.14v. Those numbers seem exactly right to me. As far as I know, my shop did reprogram for AGM battery and reset to new. Maybe it is the IBS?

[PhaseP]

I have recently found out watching the voltage on my car, the ECU doesn't turn on the alternator (through Voltage regulator) for about 10 seconds after engine starts up. My guess is this is when ECU tests battery with the whole car loading it. If it goes below some voltage during that time it maybe saying battery is not good. I suggest try to watch the battery voltage during the first few seconds of start up, with a DVM if possible. Or something like this: https://www.amazon.com/Zeltauto-Ciga...cigarette+plug
Your new battery may not be good.

[Ali-E90]

Some North American cars had a recall on the "B+ battery cable", I'd look into that first just to eliminate that from the equation.

[tom.gnade]

Originally Posted by PhaseP

I have recently found out watching the voltage on my car, the ECU doesn't turn on the alternator (through Voltage regulator) for about 10 seconds after engine starts up. My guess is this is when ECU tests battery with the whole car loading it. If it goes below some voltage during that time it maybe saying battery is not good. I suggest try to watch the battery voltage during the first few seconds of start up, with a DVM if possible. Or something like this: https://www.amazon.com/Zeltauto-Ciga...cigarette+plug
Your new battery may not be good.

I measured the voltage at startup, and it drops to about 10.8-11v for about 5-10 seconds, then climbs up to just above 14 volts. The battery light comes on every time I start the car. My shop said it could be the IBS or it could be a module that isn't turning off, but they would have to troubleshoot it since there won't be any clear cause.

Any suggestions as to how I could test the IBS? Can I disconnect it entirely and start the car? I could also just go ahead and replace the voltage regulator, since I already bought it. It sounds like it's going to be a random guess process if I bring it to the shop too, and they might just start replacing things and see what works.

The IBS recall doesn't apply to my model year, so no freebies there.

[PhaseP]

Originally Posted by tom.gnade

I measured the voltage at startup, and it drops to about 10.8-11v for about 5-10 seconds, then climbs up to just above 14 volts. The battery light comes on every time I start the car. My shop said it could be the IBS or it could be a module that isn't turning off, but they would have to troubleshoot it since there won't be any clear cause.

Any suggestions as to how I could test the IBS? Can I disconnect it entirely and start the car? I could also just go ahead and replace the voltage regulator, since I already bought it. It sounds like it's going to be a random guess process if I bring it to the shop too, and they might just start replacing things and see what works.

The IBS recall doesn't apply to my model year, so no freebies there.

I think you can just disconnect the small cable that goes into the IBS. It is the thing that is part of the negative battery post, a small cable goes into it, disconnect this. You may get codes on IBS missing. There were threads related to IBS, how people disconnected it etc. for troubleshooting

[Noir]

Another thing that may help, when that IBS wire (isn't that the thick wire off the battery?) was messed up in my e90, the sensor for the passenger airbag was constantly on along with the notification stating this on my Navi. My indy took a look at the wire and said it was fraying ( or something to that effect, its been a hot minute, sorry... ) so he cut it open, and refurbished ( so to speak) the portion that needed attention. Sorry this is difficult for me to articulate... Not much sleep last night. Hopefully this helps you somehat narrow stuff down, although this isnt an issue you are facing.

[PhaseP]

Originally Posted by Noir

Another thing that may help, when that IBS wire (isn't that the thick wire off the battery?) was messed up in my e90, the sensor for the passenger airbag was constantly on along with the notification stating this on my Navi. My indy took a look at the wire and said it was fraying ( or something to that effect, its been a hot minute, sorry... ) so he cut it open, and refurbished ( so to speak) the portion that needed attention. Sorry this is difficult for me to articulate... Not much sleep last night. Hopefully this helps you somehat narrow stuff down, although this isnt an issue you are facing.

That is not the IBS, it is the BST (Battery Safety Terminal). BST is on the positive battery post. IBS is on the negative battery post.

[tom.gnade]

So I have discovered that the voltage is draining, rapidly, while the car sits. I have no idea why yet. I don't hear or see anything running. I've had a battery charger on it all night and it is still running full tilt, which is crazy. I've checked all the lights in the car after it sat for a bit, and none of them was hot or seemed to be stuck on.

I could probably get a better voltmeter and narrow it down to one fuse, if the fuse box weren't nearly impossible to access. I suppose this is the random kind of sh*t I signed up for when I bought a BMW.

[PhaseP]

Originally Posted by tom.gnade

So I have discovered that the voltage is draining, rapidly, while the car sits. I have no idea why yet. I don't hear or see anything running. I've had a battery charger on it all night and it is still running full tilt, which is crazy. I've checked all the lights in the car after it sat for a bit, and none of them was hot or seemed to be stuck on.

I could probably get a better voltmeter and narrow it down to one fuse, if the fuse box weren't nearly impossible to access. I suppose this is the random kind of sh*t I signed up for when I bought a BMW.

Did you try disconnecting IBS? There are people on forums reporting faulty IBS causing drainage of battery. Not sure how it is possible but maybe it is causing some systems to stay on and awake.

[PhaseP]

Also do your battery get hot with the charger on? Can you charge the battery alone disconnected from the car? Do not close your trunk with battery disconnected , put a rag or something on the trunk latch to prevent accidental closing of trunk whenever you disconnect battery.

[Noir]

Originally Posted by PhaseP

That is not the IBS, it is the BST (Battery Safety Terminal). BST is on the positive battery post. IBS is on the negative battery post.

OOPS...
Thank you for clarifying!

[tom.gnade]

It doesn't look like my car has the IBS. The negative cable is just a plain connector.

[Joebie]

pull each fuse 1 by 1 while the car sits and then put an ammeter across where the fuse used to be.

Some very very small parasitic drains are normal but a "large drain" like you claim should be easily detected if its a fused circuit causing the drain.

[VXEric]

has the battery itself been tested? I know its new but AGM batteries are prone to torn separators which will cause them to lose voltage very fast.

if you can leave the battery disconnected overnight after driving (you know its fully charged) then check voltage in the morning to see if the voltage drops overnight, that will tell you if you've got an internal short in the battery. Right after coming off charge it will probably be around 13-13.5V and should stay around 13V overnight without much issue. if it gets below 12.5 after sitting for only 12 hours or so, its got an internal short (bad cell)

If the battery is good, Joester's method is effective for finding parasitic draw.