Constant battery drain
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AudiWorld Member
Joined: Jun 2012
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From: Fulton,NY
Constant battery drain
My 07 A8 battery died over the summer. Was only the second battery since new. We don't use the car much, so it was so dead that the trunk wouldn't open, so had to access the terminal on the passenger side floorboard and energize it. After installing the new battery, car made a lot of noises, and didn't start. On the second or third attempt, it did turn over and start fine. But apparently in this whole process, something got screwed up, and the battery will drain overnight. Drops substantially in just a couple hours.
Wondering if it's feasible to check somehow with my meter to find the source of drain. Just not sure where to begin. Talked to local shop, and they thought they could have a few hours into it, before even finding the problem, turning into a pretty hefty bill. Any ideas appreciated!
Wondering if it's feasible to check somehow with my meter to find the source of drain. Just not sure where to begin. Talked to local shop, and they thought they could have a few hours into it, before even finding the problem, turning into a pretty hefty bill. Any ideas appreciated!
AudiWorld Senior Member
Joined: Apr 2009
Posts: 639
Likes: 72
From: Tucson, AZ
If you have VCDS it will pinpoint any modules that may be causing the issue. Otherwise it's a shot in the dark. If you don't have the tools to troubleshoot then it might be easiest to take it to the shop.
Thread Starter
AudiWorld Member
Joined: Jun 2012
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From: Fulton,NY
Thanks,
Tim
AudiWorld Wiseguy
Joined: Aug 2012
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From: Chicago
You can just use the blade key to manually unlock and open the trunk. No need to mess with footwell connections.
How long did you run the car with the new battery? Enough to fully charge it? You should also code it in with VCDS to reset the battery energy management module and ensure optimal performance and charging profile.
There’s every chance that the car still thought it had a bad battery so it commanded the charging system to go full power for too long, overcharging and damaging the new battery.
A bad alarm siren battery is also a common cause of battery drain. The siren battery isn’t user replaceable. Needs a new unit.
How long did you run the car with the new battery? Enough to fully charge it? You should also code it in with VCDS to reset the battery energy management module and ensure optimal performance and charging profile.
There’s every chance that the car still thought it had a bad battery so it commanded the charging system to go full power for too long, overcharging and damaging the new battery.
A bad alarm siren battery is also a common cause of battery drain. The siren battery isn’t user replaceable. Needs a new unit.
Thread Starter
AudiWorld Member
Joined: Jun 2012
Posts: 90
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From: Fulton,NY
I appreciate the ideas. When I tried to start the car before, it wouldn't start, and wouldn't allow key to be removed from ignition, either. Hence the footwell solution, which I hate doing. Should have just used keyless ignition.
I didn't run the car that long, as I figured the battery was pretty full when I got it. I've slow charged it, and disconnected from car holds fine. I'm trying to get in touch with another shop I've used in the past that's really good, so hopefully they can diagnose and correct it.
Thanks
I didn't run the car that long, as I figured the battery was pretty full when I got it. I've slow charged it, and disconnected from car holds fine. I'm trying to get in touch with another shop I've used in the past that's really good, so hopefully they can diagnose and correct it.
Thanks
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