Been there, done that! Bought one for the wife for light decorative trimming. It cut very well, is very light and the battery holds up very well. The Mrs used it for two short seasons. At the beginning of this season (third season) it ran for a few minutes then quit. It was purchased in May of 2014 so it was out of warranty.
I called a local Stanley/Black and Decker repair station and was told that B & D supplied zero parts for that unit. I took it apart and it was pristine inside. This did not settle well with me. Two short seasons of light trimming for $90. So I called B & D to complain. They told me it was most likely the battery (even though I knew it wasn't) and sent me a new battery, gratis.
It did not work (as I knew it would not) so I called them back up and they agreed to send me a new trimmer. You can buy bare trimmers on Amazon for $55. They have no battery or charger. When the trimmer arrived, it was complete with battery and charger. I now have 4 batteries and 3 chargers as I had purchased their handy little blower that used the same.
They also told me that that model of trimmer was now discontinued and they were waiting to deplete existing inventory. They said there will be a replacement but stated that they were getting away from that 20v battery. I do not think I got the whole story but at least I have a new, handy, lightweight trimmer for the Mrs to use. They are considerably lighter than other brands.