Bought the bare tool since I already have batteries and chargers for my other tools. Description says to use a 9.0 battery but I can trim my yard with a 6.0 battery- about 2 acres. If you trim more than this I would go with the bigger battery. Otherwise this trimmer has as much or more power than the 25cc gas model it replaced. String replacement is the easiest I have ever seen on a trimmer- don’t even have to remove the spool from the machine. Well balanced and lighter than a gas one too.