Battery Audi battery intermittent drain

justray · Mar 12, 2015

Audi A6 – 2007

Since I bought the car 2.5 years ago at a main Audi dealership it’s had an intermittent battery drain which I’ve tried all sorts to trace. It’s getting steadily worse and none of the ‘standard’ techniques have traced it yet, mostly due to the intermittency of the fault. The dealership has had the car for two days & unable to trace either – not an easy one ….

· The battery was replaced when I bought the car.
· Often the car will sit for a week staying at 100% then hours later it’s at 10% (regardless of how much the car is used) before Canbus arrests the drain (I think) allowing it to always start. The fact it ALWAYS starts makes me think the Canbus is ok.
· There was a recall for water leaking into the electrics which has been done but I stripped it all out myself & double checked - dry as a bone with no water marks.
· The car is stock, nothing changed at all except the towbar, which was fully electrically checked recently.
· I’ve tried to check the battery with a multimeter but both times had nil readings and both times got a spark across the terminals and probe wire heating before disconnecting in case of a short or multimeter damage!
· The fact that the battery has been depleted so many times now (approx. twice a week these days although it doesn’t get driven much) makes me suspect the car’s battery meter. The indications often don’t seem to add up: very fast drain on some occasions, varying rates of recharge more often than not and the fact that the battery has taken such a beating and not given up the ghost yet.

Any thoughts folks?

Leesparkykent · Mar 12, 2015

Have you taken it to an auto electrician?

Octopus · Mar 12, 2015

Have you tried the Audi forum?

Modern cars are too complicated!

telectrix · Mar 12, 2015

might be a long shot, but, considering it seems to be sometimes a hefty drain ,a possible intermittent fault on the alternator.

ifindoubtdont · Mar 12, 2015

A very quick google and it looks like it's not going to sleep properly. An interesting read when you understand whats going on.

justray · Mar 12, 2015

Many thanks for the replies folks

Leesparkykent - I've no-one locally (inside 60 miles) I can leave it with for a while as I'm in the North of Scotland & my local guy closed down.
Murdoch - Posted on several Audi forums to no avail
Telectrix - with the lack of a good local leccy I was kinda hoping the Audi dealers might have picked up on that one
ifindoubt - can you post or send me that link please?

tommholmess · Mar 12, 2015

I had a similar issue with an irregular power drain on a Polo, turns out the radio has a power adapter on the back that sometimes doesn't shut down the feed to the radio or the 12V to the aerial when the keys are removed, I played around with it for a bit and it seemed to fix the issue for a few months, then just changed the adapter and not had an issue since!

Gazthesparky · Mar 12, 2015

justray said:
Audi A6 – 2007

Since I bought the car 2.5 years ago at a main Audi dealership it’s had an intermittent battery drain which I’ve tried all sorts to trace. It’s getting steadily worse and none of the ‘standard’ techniques have traced it yet, mostly due to the intermittency of the fault. The dealership has had the car for two days & unable to trace either – not an easy one ….

· The battery was replaced when I bought the car.
· Often the car will sit for a week staying at 100% then hours later it’s at 10% (regardless of how much the car is used) before Canbus arrests the drain (I think) allowing it to always start. The fact it ALWAYS starts makes me think the Canbus is ok.
· There was a recall for water leaking into the electrics which has been done but I stripped it all out myself & double checked - dry as a bone with no water marks.
· The car is stock, nothing changed at all except the towbar, which was fully electrically checked recently.
· I’ve tried to check the battery with a multimeter but both times had nil readings and both times got a spark across the terminals and probe wire heating before disconnecting in case of a short or multimeter damage!
· The fact that the battery has been depleted so many times now (approx. twice a week these days although it doesn’t get driven much) makes me suspect the car’s battery meter. The indications often don’t seem to add up: very fast drain on some occasions, varying rates of recharge more often than not and the fact that the battery has taken such a beating and not given up the ghost yet.

Any thoughts folks?

Do you have the Audi Bluetooth module fitted to the car ?

These have been known to go faulty and not shut off when the key is removed. This then drains the battery