Just to inform, here is a small "smart" charger I bought from Audi to maintain the battery during winter time. You will notice it looks like the one from Porsche (in fact it is the same) except that the name Porsche is not on it... and that it costs at least 40 Euro less. It works also for a lot of battery types.
I am not driving the R8 for now on because of the salt on the roads here, but also due to the quotation I got from the dealer for winter tires: 5932 Euro for 4 18" !!!
btw, I have now 1300 km done, and good news: no oil (Castrol 5W30) consumption at all.

Happy new year to all of you !