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Discussion Starter · #1 · (Edited)
BMW offered to provide the extensive diagnostic report I paid for.
They asked what written diagnostics I desired.
How does this sound (what would you change)?

How to really check why a 2002 BMW is on its 3rd battery:

1. Quiescent system (post 16-min shutdown) current draw (e.g., 100 ma).
2. Normal alternator output with 14.6 volt fully-charged battery (e.g., 15.2 V, 15 A).
3. Max alternator output with simulated 0.25 ohm dead battery (e.g., 18.1 V, 80 A)
4. Starting motor current draw (e.g., 100 A)

What else should BMW check to see why this BMW is on its third battery?

http://www.bimmerfest.com/forums/showthread.php?t=92098
 

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Discussion Starter · #2 · (Edited)
Since nobody on Bimmerfest "BMW General" seems to know engine electrical test procedures, I'll move this request over to the 5-series forums so as to get some data for 5-series owners.
In the meantime, I dug up some related BMW ENGINE ELECTRICAL & DIAGNOSTIC PROCEDURES & TEST SPECIFICATIONS which may be of general interest to those on this "BMW General" forum.
These multi-page PDFs contain a wealth of hidden information not provided in the Bentley manuals, it appears.

HOTLINE INFORMATION (HLI) BULLETINS:
- "Flat battery, E39" HLI 61 13 85 000
- "Battery discharge with key in lock" HLI 61 53 89 000
- "Flat battery; Battery master switch not installed" HLI 61 36 79 000

SERVICE INFORMATION (SI) BULLETINS:
- "Battery tester" SI 61 01 02 (804)
- "Battery charging calendar" SI 61 03 98 (387)
- "Notes on charging the battery" SI 61 08 01 (776)
- "Lead-calcium batteries" SI 61 06 96 (110)
- "Off-load current measurement" SI 61 03 99 (474)
- "Battery master switch (mechanical)" SI 61 02 98 (313)
- "Battery basics" SI 00 09 01 (683)

In addition, I found some surprisingly interesting current, voltage, and specific capacitance requirements which I'll post separately to the 5-series forum as the values I'll post only pertain to 5-series owners.
 

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Shaftdrive,

By now, after your own extensive research, you probably know more than your own BMW technician...

The fact that THEY ask YOU what do you want to see on the extensive report... It says to me that they have no clue what to check. Mechanics are good with mechanical things. Things that they can see how they move... :) They can't see currents and voltage.

So I think you are on your own on that one. I think that somehow you'd need to take the lead on trouble shooting that problem and tell them what test to run.

Everything you mentioned on your list sounds like a good idea to test.

I would approach it this way first: it is one of two. Either your car drains the battery too much, or your car does not recharge to battery enough. Right? Your approach should be to establish first which one of the two is it.

If you're lucky, while trying to find out which one of the two it is, you'll find the reason for the problem. If you are not "lucky" in that way, at least your would eliminate 50% of the possibilities.

Makes sense?
 

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Another thing that I just remembered. At one of the posts M.Wong identified your battery as what seemed to me as a smaller then what it should be.

Search my previous posts about batteries for E39.

Thats what in my car. Is that what you have?
 

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Discussion Starter · #5 ·
Thanks MatWiz for the additional insight.
Your acumen goes beyond the obvious as you nicely surmised the situation.

The battery I have now is the same as yours above.

But, the battery that was in the E39 I bought in March was a smaller BMW battery.

That makes the battery I have now the third battery for a 2002 with 30 thousand miles. Kind'a fishy if you ask me.

I'm still diggin' for information (these BMW PDFs each refer to a bunch of other PDfs so the parent-child tree braches out confusingly pretty quickly).

My appointment is next week back at the dealership so I hope to finish my research before then. :)
 
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