Giblet

Last year I replaced the battery in our 07 Q7 and recoded it with the Power Management System.

Fast forward 12 months and now it seems something funky is going on. Each morning starting out, the battery is at 100% but during the day, it can precipitously drop to 5%. Today, it started at 100% and after one stop and then driving to another place, it dropped to 60% - while the car is running.

Anyone else have this problem? I am going to pull codes tonight but the only thing I can think of outside of faulty software to measure the battery power is that the alternator isn't charging it properly.

Thoughts from the collective?

Jusforfun

Could be faulty door locks. Seems an unlikely candidate at first but they drain down the battery pretty quick when they stay active.

Giblet

Do faulty door locks through a fault code? If so, I should see them when I run a VAG report, right?

Jusforfun

Sorry for no reply. I have no idea but I doubt it as they still work it is just they stay active and drain the battery. It is not a problem in later MYs or later replacements. Early replacements failed again.
I read somewhere that the fault was actually in the sensor meaning it still thinks the door is open. I dont know how that would work as the interion lights go off, perhaps they are on a different circuit.

There was one other culprit in early Q7 production, the ignition key unit. Some of the first ones did not have a proper earth connection, they also caused erratic battery drain.
Any solution to report yet?

Giblet

My wife (it's her car and therefore she has skin in the game) is watching it closely. So far, it hasn't stranded her and it does seem very erratic. The code I pulled seemd to indicate that the issue would only impact convenience features. Let's hope it is right!

Giblet

So after dealing with the issue for a couple of months, I took the Q7 in today. Diagnosis is...the battery management system needs to be recoded and (here's the kicker), the amperage level on my 1-year old battery is now too low for them to successfully do that so I need to buy another new battery. Sounds like a fine scheme to me.

So there went $175 bucks last year... I have a battery that is at 80% strength but not "good enough" to fix the battery mgmt system so I am out of luck.