The batterylevel in my A4 B8 1.8 TFSI is always indicating 100% on MMI, even when I'm sure it isn't at 100%

The battery does not have a BEM code, but was entered as a generic type.

The problem now is that because it is showing 100%, the car will not try to charge the battery.

Is there a way to overcome this problem, maybe forcing the level to be less? I do have VCDS.

Edited December 17, 2025Dec 17 by madfred

Was the battery coded to the car? It needs to be.

Yes, it was coded.

In that case I am at the limit of my knowledge and can not help.

Ok, thanks anyhow.

Merry Christmas and a happy Newyear.

I purchased another, used battery. This one is an original Audi (Varta) battery, I also purchased the negative cable with the BMS in it. I am recharging and reconditioning the battery right now.

I will install the battery and the cable within the next couple of days. Hopefully that will solve the problem. 

13 hours ago, madfred said:

I purchased another, used battery. This one is an original Audi (Varta) battery, I also purchased the negative cable with the BMS in it. I am recharging and reconditioning the battery right now.

I will install the battery and the cable within the next couple of days. Hopefully that will solve the problem. 

Are you charging it off the car or on the car ? 

I am charging it outside the car using a CTEK MX 5.0 charger.

Actually I was charging it, the cycle has already finished. I will install the battery later today.

Edited December 18, 2025Dec 18 by madfred

14 minutes ago, madfred said:

I am charging it outside the car using a CTEK MX 5.0 charger.

Actually I was charging it, the cycle has already finished. I will install the battery later today.

Then you'll need to reset the BMS . 

What is the reset procedure for the BMS?

Edited December 18, 2025Dec 18 by madfred

I found a description. Remove/disconnect the battery, wait at least 30 minuten, reinstall/reconnect the battery.

Another question, when recharging the battery whilst in the car, the plus of the charger has to be connected to the plus of the battery. The negative has to be connected to the negative of the battery (bypassing the BMS) or to the ground, including the BMS in the circuit.

I assume the BMS is the small unit integrated in the cable from the battery negative to ground?

Positive to battery , negative before the BMS sensor .  If you've jump start  pegs use those .  If you charge directly to the battery ,the BMS does not recognise the charge and carries on as before . BMS is reset using an OBD2 scanner. 

OK, got the charging part, thanks for clarifying. 

About the BMS reset, do you know the procedure when using VCDS?

 

No.  But it can't be too difficult. 

Ok, thanks for your help so far!

I installed the "new" battery, also another ground cable with the BMS was installed. 

Apparently the BMS is reset when adapting the new battery by entering the BEM code as shown on the battery.

The battery level is still showing 100%, but that might be correct. I will have to monitor the battery level the next couple of days or so to see what happens. 

35 minutes ago, madfred said:

I installed the "new" battery, also another ground cable with the BMS was installed. 

Apparently the BMS is reset when adapting the new battery by entering the BEM code as shown on the battery.

The battery level is still showing 100%, but that might be correct. I will have to monitor the battery level the next couple of days or so to see what happens. 

BMS reset , adapting , coding , all the same thing tbh.  If you charged it to 100% and reset the BMS ,  it should now see a new battery and charge accordingly.