Need help with battery drain

[subliminal]

I recently picked up an Audi A3 2.0t automatic, I have been working on fixing small things on it and just today I ran into a new issue which I could use some help on. When I went out to start it today the battery was completely drained after sitting overnight, I threw a spare battery I had in it and it started right up and I went to work. When I went to leave work the battery was once again completely dead and the car had no power whatsoever. I got a coworker to give me a jumpstart and I was able to get it going to get home. I thought maybe my bluetooth fm transmistter was draining the battery so I unplugged it and went to check on the car about an hour later and once again it had no power at all. There doesn't appear to be anything on when turn off the car.

The other day I was working on the car and removed the battery and the battery tray and while I was putting it back together and tightening up the battery the socket wrench slipped and touched the two terminals of the battery together for a split second, the car started fine after this and it was only for a split second but Im wondering if that incident may be related to my battery drain and if so what areas do I need to check? Thanks in advance for any insight you can give me.

[Epic-A3]

I dont think that fast of a short would cause a drain, if anything it would blow fuses. Unfortunately a parasitic drain is hard to find. 1st thing, is there any after market stereo work, or lights added, or ever wrecked?
Small things you can do- get a clamp on amp meter and clamp it around the negative cable. See how big the drain is. Next, go to the fuse box, both inside and under the hood. You'll have to pull a fuse and check the meter again to see if the number went away, replace the fuse if the number is still there on the meter. Repeat this with all fuses if necessary. Once you pull the fuse that makes your meter show zero amps, you've at least isolated it to the system it's in.
Draining at that speed, it must be a pretty significant drain.


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[Epic-A3]

1 other possibility is, if a diode goes bad in your alternator... it can literally empty your battery to 0 volts. Also with a volt meter you can check this. Turn the car on, you should have roughly 13.8- 14.5 volts DC with the engine running. Now with the engine still on, switch the meter to AC. If there is any AC voltage showing, you alternator has a bad diode. A diode is basically a check valve for electricity, letting it flow 1 way only. If it goes, it can destroy your battery and drain quickly while the engine is off.

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[Creations_Cult]

[QUOTE=Epic-A3;13759852]I dont think that fast of a short would cause a drain, if anything it would blow fuses. Unfortunately a parasitic drain is hard to find. 1st thing, is there any after market stereo work, or lights added, or ever wrecked?
Small things you can do- get a clamp on amp meter and clamp it around the negative cable. See how big the drain is. Next, go to the fuse box, both inside and under the hood. You'll have to pull a fuse and check the meter again to see if the number went away, replace the fuse if the number is still there on the meter. Repeat this with all fuses if necessary. Once you pull the fuse that makes your meter show zero amps, you've at least isolated it to the system it's in.
Draining at that speed, it must be a pretty significant drain.


I personally have ran into parasitic drain issues on my e46 330i and some on my 8P. With my e46 I was out there testing the voltage and I did exactly what Epic-A3 was saying and tested every fuse to see what was draining my battery, turned out the light inside the glove box wouldn't turn off because the switch broke and that light was draining the battery it was a little difficult because you couldn't see the light on with the glove box closed (when it should be off) and because there was no fuse for the light inside the glovebox.
My Audi started draining it's battery after someone clipped me while I was sitting at a stop sign, I bought a brand new battery and replaced the one that was in there with one from walmart because the battery kept draining. The walmart battery worked long enough for me to repair the car and get it running and street legal again. After I had the car running I noticed my battery was still draining even tho nothing was on I had no shorts really, but I did have a bypass of the inertia switch so that the car would start with a deployed airbag. I ended up buying a new battery from Audi Riverside and called it a day. I guess the Audi batteries are supposedly a battery with a drain tolerance built in so, the battery doesn't drain from auxiliary electronics running after the car is off and everything is off.

[Epic-A3]

So what I do for a living is a battery specialist. Just FYI for everybody. No battery is exempt from draining unless there is a cur off switch. No matter the make or model of battery, even lithium batteries lose charge from parasitic drain and they lose voltage just sitting around doing nothing. So weather an Audi battery ( which is made by Varta) is really no different from any other battery. The best kind of battery for our cars is an AGM ( absorbent glass mat) they have the capability to work as a starting or deep cycle battery. All that means for us is, if there is a small drain or it sets alot like winter time it can handle the punishment alot better. Its not fool proof but does help. You still need to charge every 30 days if your not running it. If you cycle a normal battery like from Walmart to much, it destroys the battery inside creating a bad cell or fast sulfation on the plates. Boring stuff, but our cars need them to start the show. I hope you can find your drain. I know it's a pain in the ass like Creations_Cult was saying.

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[subliminal]

1 other possibility is, if a diode goes bad in your alternator... it can literally empty your battery to 0 volts. Also with a volt meter you can check this. Turn the car on, you should have roughly 13.8- 14.5 volts DC with the engine running. Now with the engine still on, switch the meter to AC. If there is any AC voltage showing, you alternator has a bad diode. A diode is basically a check valve for electricity, letting it flow 1 way only. If it goes, it can destroy your battery and drain quickly while the engine is off.

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It looks like you were correct about the diode, I tested it and it was positive for a bad alternator. Replaced it and it seems to be fine now. Thanks for the help!

[Epic-A3]

No problem. That stuff can be frustrating.

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