Black Decker RB-3610

We have a large estate requires several hours to cut the property. Mower original battery does not last long enough to cut all the grass. On the other side of batteries and chargers, you can cut two times before the batteries ran out of juice to go. Can I provide two batteries, use the charger with a second battery in the cutting process much better. Fantastic second battery, I would definitely recommend the battery and charger. Black   Decker RB-3610 , Black   Decker HPNB24, Karcher K 2.28,Weed Eater 952711937 , Black   Decker LST1018