Can I also use the Wiesel for charging large batteries?

Basically yes; despite the longer charging time the quality of charge will be very good with a Wiesel V3 sold in the year 2012.

However with older Wiesel chargers sold before the year 2012, capacity losses will occur when charging large lithium-ion batteries (capacities of 7.5 Ah and up). The reason is that the charging current is not sufficient for fully charging these large batteries. Losses amount to approximately 1 Ah with a 7.5 Ah battery.