This spring I grabbed the handy Echo battery string trimmer and no joy - battery got too low over winter and won't recharge. It was good, handy quiet for two years and now dead. Replacement battery is nearly the cost of a whole new one.
Picked up the old Echo SR-225 GASOLINE string trimmer, fired on first pull.
I think there is a lesson there: battery stuff is not as use-and-forget as gasoline stuff.
PS I only use E0 (non alcohol fuel) in my small engines.
I ran across this "jump start" technique, when searching YouTube for aftermarket battery reviews. Maybe some of our electronic smart folks will chime in on this?