Battery bad or drained?

[etcetera]

I cannot figure out if my battery was drained by something or if it's just old.

Yesterday was fine, started, today checked and it's at 8.9V.

Not sure how to interpret these codes. Appears to be an OEM battery. The PO says it's 3-4 years old but should be able to tell definitively from these numbers. There were no others codes on the battery that I could find.


http://i182.photobucket.com/albums/x260/dictum9/auto_BMW_528i_1999/battery1.jpg

http://i182.photobucket.com/albums/x260/dictum9/auto_BMW_528i_1999/battery2.jpg

http://i182.photobucket.com/albums/x260/dictum9/auto_BMW_528i_1999/battery3.jpg

http://i182.photobucket.com/albums/x260/dictum9/auto_BMW_528i_1999/battery4.jpg

[mattmartindrift]

07/06 I think is the date.

[etcetera]

So it's getting close to being 4 years old, should I go ahead and replace it?

Why did it suddenly drain like that? How do batteries go bad, do they just suddently fail or is it a slow thing? I am not sure if it's a drain thing or can it not hold charge anymore?

[jamesdc4]

Here's Q's link to instructions on determining the battery age.

Here's a direct link to a past thread that shows how to tell how old your car's battery is: http://forums.bimmerforums.com/forum...3&postcount=15 (http://forums.bimmerforums.com/forum/showpost.php?p=18325983&postcount=15)
A battery registering 8.9V is at a 0% state of charge (dead).
http://www.bimmerboard.com/members/q/original/BMW%20Battery%20State%20of%20Charge.jpg
(Table image courtesy Qsilver7)

[etcetera]

It looks like some kind of Autozone / AAP battery. It's code does not correlate one to one to this OEM one. Which number do I look at on mine? The last 4 digits of that number stamped in plastic I assume?

I am thinking about taking it to AAP, having them charge it (or else tell me it's no good), then putting it back in, running the engine, checking if 14V is being supplied to the battery by the alternator. If so, there has to be a drain somewhere. If not, bad alternator.

[jamesdc4]

It looks like some kind of Autozone / AAP battery. It's code does not correlate one to one to this OEM one. Which number do I look at on mine? The last 4 digits of that number stamped in plastic I assume?
Sorry about that. I thought there might be another sticker like the one in my photo below (My car is a 98, so it's possible the last two digits of the second set of numbers might be my batt. mfg. date). I'm not sure about the set of numbers Matt mentions. My stamped code also ends with 111106 (although it makes sense if the PO replaced the battery at 7-8 years).
http://i13.photobucket.com/albums/a282/jamesdc4/IMG_1394.jpg

I am thinking about taking it to AAP, having them charge it (or else tell me it's no good), then putting it back in, running the engine, checking if 14V is being supplied to the battery by the alternator. If so, there has to be a drain somewhere. If not, bad alternator.
You can check your battery state of charge by unlocking the OBC and using test #9. You can see what the alternator is putting out by checking test #9 with the engine running. Should be around 13.7v.
How can I tell if I have the High or Low OBC? (http://forums.bimmerforums.com/forum/showpost.php?p=16039847&postcount=12)

How do I unlock the OBC (Low and High)? (http://forums.bimmerforums.com/forum/showthread.php?p=14994497#post14994497)

[etcetera]

I used a voltmeter to check my battery voltage, it's at 8.9V.

[Qsilver7]

It looks like some kind of Autozone / AAP battery. It's code does not correlate one to one to this OEM one. Which number do I look at on mine? The last 4 digits of that number stamped in plastic I assume?

I am thinking about taking it to AAP, having them charge it (or else tell me it's no good), then putting it back in, running the engine, checking if 14V is being supplied to the battery by the alternator. If so, there has to be a drain somewhere. If not, bad alternator.

I'll repeat again, what was in the link that was given....regardless of it being an Advance Auto or Autozone battery or BMW branded battery...the first alpha character represents the MONTH of mfg...and the second numerical digit represents the YEAR of mfg.

Look at your battery again for a code somewhere on one of the corners of the battery case (hopefully)...sometimes it's not there...the old battery I just replaced in my e38 didn't have the code engraved into it...if it did...I couldn't find it anywhere.

BTW...what color is the eye on the battery? Is it yellow, black or green?

[etcetera]

Update: I barely jump-started it, not sure why took a dozen tries, probably bad connection with the jumper cables.

Anyway, ran it for about 20 miles to charge the battery. With the engine running, the voltage going to the battery was 13.9V, almost 14V that is. So this proves the alternator is good and is charging it.

Secondly, disconnecting the battery and checking it resulted in 12.8V. So it appears to have charged. I will check it tomorrow again to see if it still holds that charge and if it still starts. If so, the battery is fine and it's something draining it.

I think it's the tailgate problem. I started having battery problems right after this tailgate open light came up in the cluster. It's showing the tailgate open no matter what I do. I tried to close it numerous times, the lite is still there, showing tailgate open while it's closed.

Clearly, it's some kind of electrical issue with the tailgate. Does it have some kind of sensor that went bad?

I keep listening to the tailgate motor to try to close the tailgate continuously but it's completely silent after the motor does the initial close. The tailgate works though, opens and closes.

I think something is draining my battery.