Battery Drain Question

[bigtimz]

Is it an Avant?

[apole]

Mine is the saloon but not sure if the question was for me. So far all has been good with mine since I started turning off the MMi. I was poking around in the RHS of the boot the other day as the reversing light on that side isn't working. Noticed an extra cable that didn't look factory attached to one of the posts of the battery manager. When it's warmer I will investigate further, and change that bulb !!!

[bigtimz]

Apole.
Mine was an Avant so my theory is dead.
My battery drain problem pretty much disappeared after i found the rear wiper motor was full of water/ washer fluid . I drained the water out and stopped using the washer , i only had the battery drain problem once more before getting shot of the money pit.
My theory was that when the tailgate was lifted the water inside the motor was possibly causing the problem.
I had the car code read twice but nothing showed up. Hope you have found the problem and that it does not bother you again.

[apole]

Update:

Well I thought all was well, then the day after a long drive the battery level in the MMi was showing low charge again.

I am not sure as yet what the root cause is. I have put another post up about firmware on the battery controller and plan to do some more research.

So far the facts are:

MMi level on first blob (car starts fine). Battery voltage after car unused overnight is 12.69v direct at battery terminals. That is OK and conflicts with MMi.

Engine running for 2 mins, voltage 14.3 so indicates charging.

I then proceeded to check current draw in the boot fusebox ensuring all things off and car settled. No circuit had any significant power drain so that indicates radio, nav etc are not to blame.

At the battery level however there was an initial drain of 6.43 amps, which after a few mins reduces to 0.63 amps, still too high. So it would appear that in the time I tested something is gobbling up power !! That could well change as things get switched off by battery controller.

Nothing logged in the VCDS scan.

I will check all other fused circuits when I get time to rule them out.

I have to admit I dont' fully understand the battery controller operation, but the terminal voltage was good this morning, and conflicts with the MMi display. Against that the drain is too high, that could just be until something gets turned off after time, or indicate an issue.

Also I tried to charge the battery yesterday afternoon using the terminals provided under the bonnet. This didn't do anything and it appeared that something was either drawing more power than charger (quite pricey 16amp automatic model) or stopping the charge occuring. It was on for 4 hours and the MMi and charger display hadn't moved at all.

On disconnecting the battery to test power draw I noticed on reconnection the MMi display had gone up to over 50%, with no charging or engine running.

Bit suspicious of the battery controller, maybe it's faulty or needs an update. Or it could be the battery charge level is low so the controller is doing it's job and limiting circuits so my readings do not show true readings.

I'll check what I can then if it's beyond me I'll get my local specialist to investigate.


Will keep you posted.

[singhl]

The battery manager has a software fault - it will show inaccurate readings, my one said 20% for one week, the car started fine, battery was at 12.6v at rest, when i unplugged the battermanager lead (by the metal stud) and left it for a while and plugged back in , it showed 80% without charging battery. So it can show a rubbish reading. The drain is from sat nav and audio, you can pull the fuse out if doing current draw test, and it will confirm it.

That is why i have a relay on that fuse.

[joshA6]

The battery manager has a software fault - it will show inaccurate readings, my one said 20% for one week, the car started fine, battery was at 12.6v at rest, when i unplugged the battermanager lead (by the metal stud) and left it for a while and plugged back in , it showed 80% without charging battery. So it can show a rubbish reading. The drain is from sat nav and audio, you can pull the fuse out if doing current draw test, and it will confirm it.

That is why i have a relay on that fuse.

not that it solves the problem, but battery manager is completely useless as a gauge to your battery, You are on the right lines with the testing you are doing. Get the battery testing at an auto shop which can simulate its cycle capacity. It may still be goosed. I would suspect batter controller or possibly a bad earth strap etc if the battery is still deemed OK.

Are there any other fitted accessories (DVD Players etc) that are non standard?

[apole]

Hi, the battery is new and genuine Audi. I'm more convinced it's down to the battery controller, today I set off and car hadn't been used and it showed 100% in MMI, got 10 miles to destination, went in for 10 mins, came out battery low and 1 bar on display !!

I have pulled the 2 x 5amp fuses to the Nav and radio singhl suggests as a test, the voltage at the battery is still good. If that proves to be the root cause I can wire those via a relay fairly easily.

There is nothing that wasn't fitted from the factory on the car, bar the bluetooth that was fitted afterwards to the MMi bu Audi.

I will work through all the fuses to check for a drain when I get time but so far so long as the battery has good voltage and the car starts and runs fine I'm OK, it's just annoying.

I did check all the connections I could the other day to rule something simple out.

I have done a wider web search on the issue and there are quite a few posts about this. In summary there are TSB's on the battery controller (aka energy management control module), advanced key control module, and a batch of duff radios that do strange things when it's cold. I know I the MMi software is quite old, but the rest need Audi to look at as they have access to online software version management. Good to know, will try the simple stuff first though and double check the new battery was coded in correctly.

Thanks for the help and will keep you posted.

[singhl]

forgot to mention the latest MMI update (5570??) has an update for the radio/audio, and worth doing this, also 5570 is last update that audi will do.

[apole]

Update:
I have had the 3 fuses for the audio and nav removed for a few days now. Noticed 2 things, firstly the battery has stayed full which is great news, secondly when I first removed them I then reconnected my battery charger. Instead of this getting nowhere in terms of charging, it did what it should do and charged the battery to full where it cut out.

So this indicates that as Singhl has said the nav and audio are the culprits to my battery drain issue, and also take power that exceeds what my charger can provide, therby making recharging impossible. I'd put this down also to the charge controller not turning that circuit off as it should do.

One other things I've noticed is that I have the BOSE upgrade. That is on an adjacent 30 amp fuse. If I just have the 2 5amp fuses for the audio and nav out you can hear a clicking from the amp in the boot. Removing the 30 amp fuse for the amp stops this.

Singhl, do you have the BOSE amp in your car? I am thinking to add this to the other devices on the ignition switched relay as it must be taking power too.

So the fuses in question in my car are on the right hand side of the boot, behind the cover, in the brown section of the fusebox as follows:

Fuse 5, 5 amps for communication
Fuse 7, 5 amps for navigation
Fust 8, 30 amps for BOSE amp

I have bought a 40 amp relay, a 4 way waterproof fusebox and suitable cable and connectors to make up a ignition activated circuit for the above. All will be properly fused.

Won't do this until I have more time and it's a tad warmer but happy to take some pics and post up if anyone needs.

Thanks again to for all the help, especially singhl, this was all really helpful.

[singhl]

No - i do not have a bose amp - just the stock one that is not marked as bose, but there is an amp - glad you have found a solution, also make sure you have updated the mmi software to 5570.