The issue is some type of feedback system the charger uses. I don't remember specifically about the graupner. I think (not sure) that the graupner is the same as the shulze (is that true?) if it is then you are ok.

There is some sort of charger that has a feedback issue. (Bob Wilcox knows and told me about it, but the name escapes me becuase I didn't care when I found out my chargers would work no issue) but it's a feedback thing.

Anyway, I believe you are in no danger of blowing anything up if the graupner is that high end charger that is the same as the shulze.

Somone else or you can verify that point.

Sean