It depends on what ohm coil you use, and the PG/VG ratio.
The following is the recommended voltage, for Aspire's Bottom Vertical Coils (BVC) atomizer:
Code:
Ohm (O) Voltage (V) Watts (W)
1.6 3.0 4.2 4 - 6.5
1.8 4.2 5.0 < 15
2.0 5.0 6.0
Aspire recommends keeping the VG below 50%