My machine has been sitting for a week, I went to start it this morning and was slow turning over and would not start. I charged the battery for a few minutes and it fired right up. Drove 1/2 mile to my neighbors to return a tool and when I left headed for home it sputtered the whole way. It seems to start fine and run OK below 10-15 mph or so but if you get on the gas a little it begins to cut out, it sputters almost like in reverse. Any ides what is going on with my machine? It ran fine until today.