if it is an ego style battery the 5 on/off thing is to turn the battery off and on for transporting, when on you have to hold the button down to take a drag. 1.8 heads will work fine usually they recommend the 2.0 or higher for the spinner and twist so you have more range to play with the voltage. as 1.8 is on the lower end and wont leave much room to go to high if you have an adjustable voltage device.