After charging the vehicle. We reversed out of the parking stall. The vehicle braked really hard with no warning as if we hit something, but there was nothing for us to hit in the parking lot. The braking was so hard my body jerked! This is the second time the emergency braking engaged sudden. The first time a vehicle was near and the warning light did indicate vehicle but not close enough for the braking system to engage. It could have caused the vehicle to hit me from the rear if it was closer.