OH BOYEEEE....another volt, ohm, power, amps, watts discussion
eGo Twist, max volts from full charge is 4.2vdc...in fact ALL Li Ion batteries...MAX charge = 4.2vdc when it is discharged to safe level (if you OVER discharge a Li Ion battery, it might not ever charge again safely [imagine your lungs..you breath in and out in a certain range...breath in too much...pop a lung, breath OUT too much...might not be able to breath back in again...collapse a lung] sorry for the image but it's the best analogy I can come up with) max discharge of Li Ion is 3.2vdc
The twist is a potentiometer (electronic throttle), it actually REDUCED that 4.2vdc down...so with the above chart and whatever resistance coil you have, you can dial the volts down to meet with the resistance to push a certain amount of electricity (called current) thru the coil wire...the resultant current (A) times the voltage (V) gives you the power or "heat energy" (watts) the coil is making...
It allows you to use lower resistance coils then adjust the power your rig is applying...without the ability to adjust...just pushing the button pushes the max available volts the battery has in it...a car with no transmission or throttle...turn the key...car starts and off it goes wide open until you turn the key to turn off the engine (release the button)...
Variable Voltage allows you to tune the performance of your power...a car with a throttle and a key, so now you turn the car on it takes off but since you dialed down the throttle it ain't wide open, you can then apply more throttle if you want. Push button, start car..it takes off but slower because the throttle...push gas...more throttle which equals more "power, (release button), car stops...
Variable Wattage is a car with a key, throttle, AND transmission, you can adjust it thru an entire range of settings..more often than not you can set "cruise control" and even if you change the head (go up or down a hill) the car will auto adjust to maintain the "power"
Hope that helps