I ran some battery size calculation and found that if the ATV will be used on flat ground with some hills then a battery pack made from two 12V 15Ah batteries will provide a little under an hour of ride time, and a battery pack made with two 12V 22Ah batteries will provide around 1-1/2 hour ride time. These ride times will be a little longer if the ATV is driven only on flat ground or at less than full throttle.
Recharging batteries slowly increases their lifespan so we recommend a slow charge when possible however we sell battery charger that can recharge them slowly or quickly. A slow charge is in the 5 to 6 hour range, and a fast charge is in the 2-3 hour range. These charge times apply to both 15Ah and 22Ah batteries.
Please let us know if you have any questions.