A8Pete

My A8 has been off the road for a couple of months and the battery has gobe completely flat. Batter is one year old.

I have opened the trunk (with the key as central locking is not powered and connected a battery charger negative to metal post and positive to the battery.

There were a few relay clicks for a few minutes but they have stopped.

How long before the central locking starts working again?

I have tried the iginition key in the drivers door to open it but that doesnt seem to work. Any thoughts?

haggisuk

Depends on how long it takes for the battery get up to a sufficient level but if the battery is completely dead your flogging a dead horse.

Best get a new battery in her and keep it charged going forward

blankhopp

When I needed to recharge my battery it took 4-5 hours from beeing totally empty. If it doesn't charge I would go for a new battery. The bad battery in my car gave me lots of faulty codes that were just gone when I put in my new battery.

A8Pete

Thanks.

I shouldnt have left it. The battery is less than a year old. Hopefully it will recover, if not its a trip to the local battery supplier.

Cheers

PS. Any idea on the key for the manual entry on the drivers door. It doesnt seem to want to open.

the_duke

Unhook the battery while charging and it will charge faster.

uberwgn

Pete, they don't want you connecting a charger directly to the battery. They want you to make the connection under the hood on the two charging posts.


(I suspect they don't want a direct connection to the battery due to potential damage to the BEM. This is all outlined in the Owner's Manual and our cars have stickers showing the same.)

the_duke

A8 D3 doesn't have posts under the hood. Only by the battery in the trunk.

2004A8L

How can we tell how old the battery is ? is there a production stamp somewhere on it ?

MP4.2+6.0

On a D3, you do it at the battery area. There are no under hood posts. If you read OP's first post, he did it correctly--one side (positive) to the battery terminal, while negative goes on the big grounding hex shaped post. You want the battery hooked up so the battery manager knows its state of charge. That's the basic reason to attach at metal post on negative side, putting aside the slight difference for spark setting of hydrogen gas scenarios that is dealt with by simply not plugging in charger until hooked up or before disconnecting.

Back to OP, given he connected it correctly, I wasn't sure what was wrong if anything. Door locking does get sacrificed along the way of scrubbing off power loads by the battery manager. By now should either be charged back up, or conclusion reached the battery got trashed by full discharge.

Shark_V8

Quick note about flat batteries (I have 3 types of chargers now...) -

Smart chargers will pulse charge initially to de-sulphate plates, as sulphation occurs when they are stone cold dead. Sulphation is what shorts/kills an otherwise good battery.

But I've had dead flat batteries not be recognized by my Bosch charger, so used a conventional charger at 2amp, just to build in some voltage so the Bosch would recognize it, as a 12volt automotive.

I also had (too small) smart charger go at a flat battery (in the pulse mode) but after 24 hours it was ineffective, and had only raised the voltage to say 9V. That was a maintenance or small battery charger so understandable.

it depends on what you have hooked up there.