I'm looking at string trimmers.... either a 20V brushless with 5.0Ah battery or 60 flex volt with a 3.0Ah battery and charger. I've got a few 20V dewalt tools in the shop. Will the 60 flex volt battery work in them? Will my shop tools 20V 3.0Ah battery work in the 60V trimmer? Any input on cordless trimmers in general? I'm tired of working on the gas trimmer!