X5 1/5 Scale Direct Power 16.8vOperating Voltage 7. 4 16. 8v 4s max You can use a bec but NO buck reducer is rated high enough and will void warranty. If using more then 4s battery you must use seperate battery or bec Approved bec castle bec 2. 0 and hobbywing bec Direct power 15t Spline Magnetic Sensor Waterproof IP67 Operating Voltage: 7. 4 16. 8V Operating speed: 0. 091sec 60 @ 12. 6V Operating speed: 0. 078sec 60 @ 16. 8V Stall Torque: 1682oz in @ 12. 6V Stall Torque: 1876 oz