2排-9.9V (2 x 3S1P, 9.9V/4600mah ) not heavy to slash, very powerful, but you need to modify the battery tray to "strip" the battery firm into chassis. You need to buy new battery ( 26650, 3.3V/2300mah, green colour ), do not buy those cheap battery becasue these are all re-cycled battery, some even cannot chage up, waste of money ( I waste some money before ....)