I'm going to help my son board his loft and as the area to be boarded is large I thought that it might lighten the load by using a cordless screwdriver. How powerful will the motor need to be? I had been looking at one in excess of 10v but came across an Energetic branded one in Screwfix that was 3.6v but the reviews seemed to indicate that it would be up to the task. Advice gratefully received.