Present work demonstrates high speed friction stir welding (HSFSW) of light weight battery trays assembly in electric vehicle (EV). Despite of solid-state and green nature of FSW, it suffers from the relatively low welding speed. With the help of suitable tool design and machine tool parameters, we successfully achieved defect-free welds at high welding speed of 4.0 and 4.5 m/min. Good quality welds are produced in 3 mm thick AA6063-T6 extruded aluminium alloy at such a high welding speeds by implementing violent material mixing i.e., higher tool rotation speeds (3500–4500 rpm) and plunge force (8.5–10.5 kN). The HSFSW cross-section registered curious hardness profile of ‘U’ shape. HSFSW resulted softening of weld stir zone (∼60 HV) along with HAZ (∼50 HV). The highest joint efficiency of 72 % was found for the weld produced at 4.0 m/min and 3500 rpm.