A robotic lawn mower includes a first wheel driven by a first electric wheel motor, a second wheel driven by a second electric wheel motor, a cutting implement driven by an electric cutting implement motor, a power system for powering the electric wheel motors and the electric cutting implement motor, and a controller configured to control operation of the electric wheel motors and the electric cutting implement motor to autonomously mow a yard. The power system includes multiple removable rechargeable battery modules and multiple receptacles, each receptacle configured to receive one of the battery modules.