Torque450

I bought a low mileage 2020 A8 from an Audi Dealer 3 hours away. I've not used the car much since, and have had the yellow low battery (will charge when driving) message. I've contacted the dealer and they've said it's fine to use my 12v AGM (Ctek) charger and drive the car in a couple of days to get the 48v charging. If not, told to take it in for 48v charging / checking.

I've read the earlier thread on the 48v issues.

My question is: If the 48v system just keeps a low state of charge, is it ok to drive it for the next month or so, and charge the 12v battery up every week until its convenient for me to take the car to the supplying dealer that I trust...?

(Its less of an inconvenience to charge it at home, than have a 6 hour round trip x2 at the moment)


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angrypengu

The 48V system typically charges at a few % per minute and it charges directly from the belt starter generator. Without the BSG working, your car will die in a manner of minutes. Remember, it's BSG -> 48V -> DC/DC converter -> 12V. This is why when the BSG dies, the car dies a few minutes later because the 48V system dies. Even if the DC DC converter tries to convert charge from the 12V system to the 48V system, it's like bailing out the titanic with a water bucket. (it will try to, and then both the 12V and 48V system die).

Your dealer is sort of wrong here. The yellow low battery light is the 12V battery that is low. So yes you can use the 12V charger you have, otherwise the car will charge that battery (or try to charge) that battery through the DC DC converter but this is not ideal. Alternators (yes, I'm referring to old school alternators) are not 'meant' to charge car batteries. They're meant to keep a full battery full. Using a battery charger is the proper way to charge a battery and that's what you're doing which is SOP.

If you find this error continues you'll need to swap out the 12V battery.

Torque450

Thanks, that's good advice. Will charge it again over the weekend.

I've spoken to the supplying dealer, and have confirmed that the likely 48v parts are available should it be the generator (I think 80% likely), before I drive 3-4 hours to them. I'll wait with the car for diagnosis then probably leave it with them until they have the parts (available from the DC, apparently).

I think this is better that it being recovered to the local dealer (40mins) who will then ignore it until the New Year when everyone's car has a flat battery etc f rom a lack of use !

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