jackso42

Hope someone can help, I've had starting problems with my Q7 for a while in that if its left to stand overnight or a couple of days it struggles to turn over on first start, usually on second start it comes to life. It has had a new battery around 8 months ago which seemed to help initially but now we are back to the square one. It has been in for it's MOT last week so I asked the garage to check the battery and they said it was fine.
Last night I charged the battery up to 12.65v and then checked it again this morning before it was driven, the battery was down to 11.80v, is that a significant enough drop to say there is a battery drain problem?, I should also add that the car always starts after a couple of go's, the battery is never completely flat. Thanks guys.

robertd

i am also quite interested in this too. Hope we will get a reply soon.

dreadlocks

when you installed new battery did they recode the ECU to reset the battery charger?

jackso42

Not that I'm aware of, I think they just fitted a new battery, they did say the battery didn't need coding as my Q7 is an early 2006 and it isn't required.

dreadlocks

you sure about that? its required for every MK1 Q7 AFIK.. the car has a battery charger in it, it ages out your battery.. if you dont reset the charger it will treat your battery as a 5+ year old battery and that will chronically undercharge it and quickly turn that new battery's performance into that of a 5+ year old battery.. all Q7's have this charger, because your battery is under your seat and if they just stick a dumb charger on it, that battery will emit hydrogen and battery acid under your seat and end up with a mess.

You need to get a VCDS plugged into it, and change the battery serial number to reset the battery charger to properly deal with a new battery.. and your gonna need another battery cuz this one is likely toasted.

It seems like your battery has a bad cell in it if its dropping to 11v quickly and if there are no new loads on it.

chingwodapigu

The shop is incorrect. All Q7s of this generation have the same battery management system that needs to be coded to the new battery, or it will charge incorrectly and eventually will ruin the new battery.

As for potential battery drains, one common issue is the keyless door handles failing which can keep the car from powering down.

dreadlocks

do 2006 have keyless? regardless, FWIW a shorted handle draining battery will show up in VCDS Scan when your coding your new battery, the quick fix is to disassemble and unplug wiring to door handle to stop the short/drain until handle can be properly repaired (if you want to on a 13yro vehicle)

jackso42

The guys who replaced the battery were so called Audi specialists !, thank you guys you've been a great help, if I get a VCDS machine myself is coding the new battery something I could do ?, my trust in my local so called Audi specialists has vanished all of a sudden !

dreadlocks

Yeah you can DIY if you get a VCDS, there are also public lists of people willing to grant you access to theirs (I'm on it for my local area, get a half dozen requests a year)

Battery Replacement - Ross-Tech Wiki

If you dont buy an OEM battery replacement, just increment the existing serial number by +1 and it should get the job done.

jackso42

Top man Dreadlocks, thanks for your help.