Damage if battery disconnected nightly?

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#1
Still trying to nail down where my overnight battery drain is coming from (posted on previous thread) on my 93 318is.

Question to those knowledgable in this area.

Does disconneting the battery posts each night and reconnecting in the morning for a 1-2 week period run any risk of long term damage to the car? Can I damage the electrical controls by taking this action or this a non-concern?


Thanks for any advice.
 
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epj3

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#2
Buy a trickle charger. Problem is probably coming from a short.

Install any aftermarket stereo's or stereo equpiment? If so, that's probably it.
 
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#3
I doubt there would be any damage to the electrical system itself. However, the battery cable ends aren't really made for lots of tighten/loosen cycles so I could see where they might get distorted, chewed up, etc.

I think I would go with EPJ's suggestion, get a battery maintainer type charger. You can get one for $25 - $40 , Quick and easy to hook up/unhook.
 
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#4
i had an issue with battery dieing after i didnt drive the car for a couple days, while i had it in semi storage. turned out to be old battery with weak cells - couldnt hold a charge.

this might take a while but you could pull one fuse a night and go by which one you did to track it down

but i would seriously take a close look at your bat.
 
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#5
Thanks for the responses.

I actually bought a new battery the first time this happened about a week ago )hoping the old battery was just shot), so unless I am really unlucky the issue is definately related to a short/draw coming from somewhere. I am still winding my way down by pulling fuses and seeing if the battery still winds down overnight (then jumping the car in the morning, going to work and then having the battery charge back up to 12 volts).

I hooked up a multimeter and pulled fuses but I did not see any noticable volt changes after pulling every fuse possible; the draw must not be large enough to swing the voltage, but large enought that it will leach the battery after 24 hours.

I have seen a few trickle charger on ebay and other sites (http://www.baproducts.com/sm831.htm) that are powered by solar energy, so you can just attach the solar cell to the windshield and plug the charger into the cigarette lighter. This seems like a perfect short term solution, as hopefully the draw is offset by the charge, and I can drive around anywhere without being tied to a plug in charger, which obviously poses more restrictions.

Any thoughts?
 
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Sethvir

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#6
On older 3's (ie 320i, '83) it was possible for the diodes in the voltage regulator to go bad and provide a path to ground when the car was turned off. I went thru 7 alternators w/ built in regulators, one after another, before getting one with "good" diodes and solving the problem. Kept looking for a short that wasn't there.

One thing I did find helpful was replacing the battery cable ends with ones that are designed for quick disconnect - they have a lever that snugs them instead of the thru bolt. I popped the cables off at night and connected the charger. It also kept the charge in the battery 'til I was ready to run the car.
 
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#8
We are on the same mindset on this.

I have still not found the culprit so I have ordered the product below:

http://www.performanceproducts.com/...ry+Disconnect&productid=100899&productType=10

It appears to allow for a easy means to toggle off the battery, but most importantly it will allow a small charge open to feed the clock, radio, ecu memory, etc. which has been a pain to deal with.

If this works as advertised I should have more breathing room timewise on trying to find the short.

I should be getting it this week; I let you know if works out (for only $15 I dont have too much on the line).
 
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#9
No luck on the product. It works well enough in that it does make it easier to disconnect the battery by just twisting a knob, but the battery still went dead.

The problem is that it seems the flow of juice that the product keeps open to keep the radio/ecu/etc live while the battery is disconnected is not limited to a certain voltage so the short/gremlin that is sucking the battery down draws as much power as it did before.

Not a bad product, just didn't work in the way I hoped to fit my admittingly novel usage attempt.
 

grc

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#10
i use a test light to identify shorts. disconnect the negative battery from the terminal and use the test light between the terminal and cable. if there is current flow the light will glow. pull fuses and relays one at a time until the light goes out. don't forget about door and hood light switches being open, you have to disconnect or block them into the off position during testing. if you take out all the fuses and relays and still have current flow, start disconnecting components like the alternator and starter solenoid. any connector you can find if you have to. digital clocks, radios and alternators are high on the suspect list. disconnecting the battery overnight with the charger on is better than just putting the charger, i think you already found out the charger can't keep up with the drain?
 
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#11
RE: Finally found the fuse that is shorted

I have finally nailed down where the draw is coming from (read a good article on this process at www.inliners.org/tech/tech6.html.

Something linked to fuse # 33 (ran the which controls the left side turn light, parkings lights, trunk lights, something called the "chargeing socket (not to be confused with the cigarette lighter) and the "door heating lock."

Does anyone know what a charging socket or door heating lock is?

I have pulled the fuse out , but I have a quick few questions:

1) I can live without the lights that the fuse controls for a while so no big deal. Question is will the battery still now be drained even though I have pulled the fuse (guess I will find out tomorrow morning if the car starts).

2) Suggestions on where the wiring for these impacted items may be situated? Is it possible that there may be a short in one of the light bulbs that I can rectify by placing new ones for each impacted area?

Thanks in advance.
 
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Hastings, MI, USA
#12
Condensed from Haynes, the door lock heating element is built into the handle assembly and is wrapped around the lock housing. The system is switched on by lifting the door handle and a switch turns on the heating element. Boy, if that doesn't sound like a battery draining device I don't know what does...
How-about the switch is faulty (stuck on or hair trigger to on) and your lock heater is on?
 
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#13
Okay if that's it, which means taking out the interior door panel and you'll have to remove the exterior door handle. Which it says you'd have to remove the window glass. This job is getting to be one that you'd at least want a manual with some good instructions or shuck out money to someone else to go after. The Haynes manual is ok, anybody got info on this from the Bentley manual?
You take all the door freaking apart, pull out the exterior handle assembly, find the faulty microswitch right above the handle, pull it off and smash it to bits with a hammer...re-assemble.
Let me know if I can help and I'll make a better pass at this, I type waaay too slow and am sans scanner at home.
 
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#14
Great feedback. Thanks. It does sound like a leech if I ever heard one.

Good news in that pulling the fuse has bought me some time. My car started right up this morning, and at the very least I can stop worrying about the disconnecting the battery each morning and having the car run rough as the ECU relearns how to drive.

I just have to live with not having a driver side turn light for the time being.

Taking the door apart does seem to be a high effort job, so I may have to go out and but the correct work book.

Nice explanation on where the door heater is, but what exactely does the heating element do? [chair] What is its function in relation to the locking assembly? Even with the fuse pulled out and the assembly disabled, my doors open just fine from the inside and the power locking mechanism seems unaffected.
 
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#15
The element is wrapped around the door lock cylinder where you stick the key. Educated WAG is that in winter this helps keep the door lock from freezing or thaws it if it has frozen. We won't need that up here until November/December and may not really need it at all.
 


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