Avoid trying to disperse bats between May and August, since this is when the pups are born. Pups cannot fly and will become trapped in the house, which will likely kill them and/or have them moving around your house.
Patch up any holes where bats could be entering the home. Anything that is larger than ¼ inch by ½ inch should be covered with caulk, expandable foam, plywood, mortar or a mesh screen. Be sure to get every entry point. Timing your bat proofing is critical and should be done during the time when the bats have all left at night.
Apply screens and secure doors, windows and vents. Also, make sure to cap the chimney if you have one.
Place a one-way opening where any remaining bats can exit the home. Attach plastic sheeting or a plastic bag to the sides of the hole (not the bottom) with staples or duct tape. The plastic should hang down one foot below the opening. The bats will be able to get out underneath the plastic but will not be able to return.
Call the animal control if you still are having problems with bats. Getting rid of bats is difficult since it takes some skill to find all of the bat entry points.