a new set of batteries will charge up to 17 hours the 1st few charges........you have to break them in right as when new they are only 70 to 75 % so the 1st 10 to 12 charge/discharge cycles are very important to the batteries preformance and lifespan, i suggest getting a charger that shuts off auto, you can ruin batts. pretty fast if you keep overcharging them,..........once you do break them in you,ll know it you,ll feel the difference...............very important to break them in right...........................