A8Pete

I had a new battery less than a year ago. Unfortunately I let the car run flat as I was working away. I charged the battery, but on the MMI interface it showed the battery as 0%.

I started the car and drive it for a few miles ad it seemed hold a charge. Next stay started fine too, MMI still showing battery as empty.

I connect VCDS thinking I might have to re-code the battery, but when I try to access module 61, power management it reports "cant access module"

After trying with the VCDS, i check the battery again and its dropped to 10v and now the car wont start.

Any thoughts?

richard-tx

I would start with installing a new battery. The battery you have should be under warranty.

A8Pete

I'll get a new battery for sure.

How does that effect my ability to read module 61 via thew VCDS. When I attempted to access it the engine was running so shouldn't there have been sufficient power? I could access other modules.

Many thanks

MP4.2+6.0

I haven't seen that before, but suspect it may be the battery manager module if you can't reach it w/ VCDS. It is back there with the battery downstream of the negative terminal, so look it over physically for any connector or similar issues. Charge battery again, and also try to access battery module while charger is still hooked up. Then you know car is powered.

If need be, take battery out and bench charge and/or test. At some point you may conclude that module has an issue. Then I would look on EBay. I don't sense it is a high demand part; in fact I don't recall any prior posts about an issue w/ it.

A8Pete

Just went out to the car again. The battery showed 10v. Tried to start the car and started first time. Measured again at the batter with engine running and got 13.38v so its definitely charging (maybe).

Wit the engine running I connected VCDS and tried to access module 61. Got the same message "module not responding". Tried a few other random modules and they responded.

MMI still showing 0%

Weird stuff.

ScottCNelson

If you connected to the negative battery terminal, then not. BTW the battery controller module is right above the neg charger lead in this pic.

File:A8 charger hookup.jpg - Ross-Tech Wiki

mishar

That battery is definitely dead. Don't waste your time with it. If you can't recode new battery check the module contacts or replace it if necessary.

aTOMic

Is the little tiny red striped wire connected to the positive terminal (at the battery end)?

Brozee

Get a new battery and avoid all the diagnosing as we know it is dead already or on it's way out. Don't push the car to charge it every time. Throw in a new one and update with VCDS.