[HJB87]

Hi guys, last week I got in the car and a number of amber warning lights flagged up on my dashboard along with a system error with my stop/start. The RAC came to have a look and told me the majority of these were being triggered by the battery running low and should be changed, he sent me all of the diagnostics. I had the battery changed as suggested however this has not solved this issue, the lights are still on. They came back to relook at the car and said all was fine and the lights were now off, great. However, last night I popped out all of the above are still on along with my stop/start and hill start not working. I have the car booked in with my garage but they are so busy they can’t book me in until end of next week. Has anyone else had a similar issue? Thanks

 

[aldfort]

If you change the battey I thought there was also some sort of "reset" process that had to be followed?

 

[RSQ3John]

Stop/Start - people who use cars for lots of short journeys do tend to experiences a downward spiral in battery voltage. The battery has to output quite a bit of energy to start the car plus all the other electrical system requirements so probably needs a 20 minute run for the alternator to re-charge the battery each time?

 

[manfrotto]

When the car detects a low battery it disables things like stop/start to conserve power. It does sound like a dud battery or battery monitoring system.

 

[spike]

When replacing the battery, the battery energy management module is normally coded to tell the system its starting with a new full capacity battery along with the amp/hour rating etc.
I can't find a definitive answer but one theory is that without coding, the system works on the old ' reduced capacity' battery parameters and screws up things like the power hungry stop start system.
If the starter really spins the engine over on a cold start and it fires up within a second or two, that suggests the replacement battery is not a dud but could point to the coding issue if the garage did not carry that out.

The second theory is that the system quickly learns it now has a new full capacity battery and adjusts the stop start logic and any other power hungry systems accordingly. I've no idea of a time frame but expect this learning process should happen after a few cold starts and several hours running.

Cheers Spike

 

[Q3hp]

When replacing the battery, the battery energy management module is normally coded to tell the system its starting with a new full capacity battery along with the amp/hour rating etc.
I can't find a definitive answer but one theory is that without coding, the system works on the old ' reduced capacity' battery parameters and screws up things like the power hungry stop start system.
If the starter really spins the engine over on a cold start and it fires up within a second or two, that suggests the replacement battery is not a dud but could point to the coding issue if the garage did not carry that out.

The second theory is that the system quickly learns it now has a new full capacity battery and adjusts the stop start logic and any other power hungry systems accordingly. I've no idea of a time frame but expect this learning process should happen after a few cold starts and several hours running.

Cheers Spike

So Spike,
I have a Q3 2012 silver SE tai 177 S-tronic and I am going to replace my original battery with an AGM Varta Start-Stop Plus 096 battery. Does that need recoding to be able to communicate with the car's PMS or it does it automatically?
Secondly, do you know if there is a radio code required for MMI system for this model? I hear from some sources that there is no code required after you replace the battery. Please, let me know your thoughts to these two issues.
Thanks, Horatiu

 

[spike]

Hi Horatiu, welcome to the Forum
Still no definitive answer on the need for battery coding as I don't recall anyone on the forum has reported back after fitting a new battery without coding it.
I suspect most of the power management criteria will sort themselves out as they will just be a function of the level of battery charge.
One negative theory I've read several times however is that as a battery ages, the optimum charging voltage changes. Without telling the system a new battery has been installed the charging rate won't initially change and may reduce the life of the new battery.
If you can get the coding done for a reasonable price then it's worth doing. If it's going to cost half the price of a new battery (or more) then it may be worth taking the risk
Option 3 is to invest in a code reader like OBD11 that will do the job

No need for radio codes as the system remembers the unit fitted to the car.

Cheers Spike

 

[Q3hp]

Hi Horatiu, welcome to the Forum
Still no definitive answer on the need for battery coding as I don't recall anyone on the forum has reported back after fitting a new battery without coding it.
I suspect most of the power management criteria will sort themselves out as they will just be a function of the level of battery charge.
One negative theory I've read several times however is that as a battery ages, the optimum charging voltage changes. Without telling the system a new battery has been installed the charging rate won't initially change and may reduce the life of the new battery.
If you can get the coding done for a reasonable price then it's worth doing. If it's going to cost half the price of a new battery (or more) then it may be worth taking the risk
Option 3 is to invest in a code reader like OBD11 that will do the job

No need for radio codes as the system remembers the unit fitted to the car.

Cheers Spike

Great, thank you for your advice. I placed an order for the reader from Euro Car Parts, only £17.99. I’ll get back to you with the reviews about the reader.

 

[spike]

Code readers in that price bracket are likely to only read and clear faults so it's worth checking if it can do the battery coding - if that's the main reason for buying.

Cheers Spike