battery woe

2000 528i (E39)
I put a new Interstate battery in this car last summer. My car gets driven about once a week. Today it would not start. In fact it was so dead, I could
not use the button on the key to unlock the door. I had to open the truck, get a jump just to open the doors.
The shop said Interstate batteries are bad, I thought otherwise. More importantly, what could be going on? Seems like something must be pulling/drwing on the battery. Also, I've noticed that when I start the car and let it idle for 2 minutes, the car seems to almost stall out or have an anemic idle.
Thoughts- af
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Even the least expensive Interstate batteries have at least a 2-year full replacement warranty. Of course, the battery will have to be tested and shown not to hold a charge. Such a new battery is probably not defective. I think you are on the right track searching for something draining it. You will need a meter to measure current and isolate any drain by pulling fuses one at a time.

Perhaps because they sell a different brand??
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Right now you only know a little about the state of the car, and you don't know anything about how it got that way.
Measuring the DC voltage across the battery cold will tell you a lot about the state of the system. And once the battery is charged or replaced, measuring the idle current being drawn by the vehicle while everything is turned off will tell you a lot about how it got that way.
The meter will tell you. The meter is your friend.
You could have an electrical leak somewhere and not know it. Things like trunk lights and glove box lights are very popular since they can be on without your ever seeing them, but things like bad alternator diodes can cause current leaks too.

I'm not a big fan of Interstate products, but your battery may be fine, just pulled down by a load. On the other hand, your battery may have an internal break and be a complete open. The meter will tell you. --scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

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Vehicle maintance has been lacking somehow.
Interstate is a real good battery source, and real good warrenty.
Take your car to them (Interstate Business Outlett or distributor garage) and have them test the battery and electrical system for free.
If they say the battery is just fine but lacking a charge, they will charge it up for you if you like ... and then you have to go to a BMW certified mechanic.
There is a hot short somewhere, or somehow battery electrons are leaking from the battery to the base plate on a string of dried hydrocloric acid waste down the side of the battery from being dirty ... which is not suppose to happen on a BMW certified mechanic work program.
They do EVERYTHING at my shop, I take my 528i to Tillman's in Santa Rosa.
They do everything, my back yard mechanic days are over with this car.
I take it in, they fix it, I pay the bill, and usually I get a loaner car to use while they have it if I ask for it.
They have to work battery to ground and trace it through the wire loom to the ignition key if it is a hot short that is burning your battery dry and can in certain very rare conditions cause fire ... maybe melting your wire loom and shorting out some wire pairs in a big way ... which you would quickly notice in vehicle operation.
So this is an easy fix IMO and all that rot ... just 20 minutes of diagnosis time to sort out why the battery is draining with the key off me thinks.
sumbuddie wear blind sea
:?
in article _azwl.13177$ snipped-for-privacy@flpi149.ffdc.sbc.com, af at snipped-for-privacy@sbcglobal.net wrote on 3/19/09 2:49 PM:

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af wrote:

Why didn't you try the key in the driver's door?
-dk
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I did. It would not open, even when using the actiual key.

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How is the alternator?? Battery voltage while at fast idle?
As others suggested, check the key-off current draw. Should be much < 300 ma.

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