You know, I purchased a B&D battery operated trimmer, single string, way back in 2010. I used that to clean up my drive and walkway on Fort Hood, and it did great in that respect. When I moved back to Maine, to a property that was way too much for the electric trimmer, I gave it to my arthritic mother. Last year I picked her up a new set of eBay Chinese batteries, and it's still going. I'm actually quite impressed with that little trimmer. Replaced her plug-in Craftsman mower with a battery powered Kobalt, and once she got the hang of swapping the batteries she grew to like it.
These things have their place, like in the hands of my mother, but they're nothing more than consumer grade items.