Black decker cordless lawnmowers black decker clm3820l2 gb p this cordless lawnmower from black decker runs for up to 30 minutes on 2 x 36v lithium ion batteries that s long enough to deal with all but the largest lawns the robust deck is ideal for mowing lawns up to 600m sup2 and the robust plastic grass box holds an impressive 36 litres the clm3820l2 has 6 different for height settings and the height of the cut range from 30 to 80mm with the move of a single lever p p the integra