Battery in the new 07 petrol for the second time defective

Hello, probably my “new” Varta is already juice and powerless again. When picking up the new car at the dealer he did not go on and a few days later it was clear that it had to be exchanged. Now I have the new about 4 months and it is probably already over again. Probably it has broken for longer and did not last more than 1 month. She is so on the edge and only in the cold start case is noticeable. Has this happened to anyone? Am I the only one? Can it be on the alternator? Mort PS: could be a part of my cause problem with Qualm (compare gas threads). However, there is something else going on there. Infos follow in the said thread as soon as I know something closer.