Use the Karcher Set WV 5 Battery + Charging Station to charge the Karcher WV 5 window cleaner. There is a replacement battery so you can replace the old one immediately. A full battery has enough energy to wash 105 square meters, or about 35 windows. Charges the empty battery while you wash the rest of the windows. This set also serves as a handy storage system, you put the window cleaner in the station when you're done. This way he charges and is at the same time stored away while you enjoy your streaked windows.