Variable voltage allows you to adjust the
voltage (or the amount of "heat") from your battery to your juice delivery device. Different
resistance (rated at a certain ohm) juice delivery devices will perform best within a certain range of voltage, and are usually categorized as either:
low resistance (1.5 - 1.9 ohm),
standard resistance (2.0 - 2.4 ohm),
high resistance (2.5 - 3.0 ohm).
The
safe vaping power chart can be used as a helpful guideline in aiding your decision of what resistance delivery device to use within the voltage range of your battery device.
http://www.ecigadvanced.com/community/guide-to-safe-vaping-and-finding-your-apvs-sweetspot/
You can alternatively start with a lower voltage setting and gradually work up to higher voltage in small increments until you begin to taste a burnt taste, then back down on the voltage setting a couple of settings. Wherever you find your particular flavor tastes best will be that flavor's "sweet spot".
I have found that fruit flavors are best in the lower voltage range (3.4 - 3.7 volts). But others, such as my coffee flavors, taste best at a higher range (4.0 - 4.6 volts). Still others, like a red hot cinnamon flavor, tastes best near 5 volts. However, your flavors and your experience may differ from mine.
Others will just take the resistance of the delivery device (ie 2.0 ohm) and add the number "2" to come up with the voltage that often works best (2 ohm + 2 = 4 volts).
Lower resistance will provide a warmer vape, generally speaking. Some vapors prefer this, others find it to be too harsh or to cause some flavors to taste burnt. Higher resistance will provide a cooler vape, generally speaking. Some vapors prefer this, as I do. I don't feel I need to replicate the heat of an anolog to enjoy my vape, but prefer a smoother vape...often with more flavor production.
There are no hard rules to follow. These are just suggestions.
