Ather 450 is not designed to draw DC power from other sources than Ather Grid or Ather Dot. You will not be able to charge the vehicle directly with solar setup. In case you use an inverter (Which you must be using for house-hold supply), you will be able to charge the vehicle at regular home charging rate as long as the available power output is in excess of the peak power input of the vehicle.
My Home runs on Solar PV system. Can I charge my 450 with that? if so, what is the DC voltage necessary?