This week on Project Farm, Todd tests battery powered string trimmers from EGO, Milwaukee, DeWalt, Ryobi, Kobalt, Makita, Atlas (Harbor Freight), Greenworks, and ECHO. String trimmers are tested for cutting speed, trimmer head efficiency at dispensing trimmer line, trimmer head string capacity, noise level, vibration, electric motor start-up torque, maximum run time, battery recharge time, and debris shield design.