The original charger transformer lists its voltage at 21.4v, but I can't find the specs on this charger, so I can only assume it's around 18v, since it says 9.6-18v charger. I charged my batteries for my Grasshog and when the charger indicates a full charge the rpm's of the weed whacker are noticable slower than the original equipment charger, so I can only assume the voltage difference in the two chargers is the problem.
This company is fantastic. I have purchased several reconditioned items and have not had a problem. The products are just like new only you pay a lot less! Do not hesitate to purchase from Reconditioned Tools.