7.4v=Rechargeable Battery, 10v=any power source from 0v to any DC voltage or just over the 7.4v. I find interesting the voltage from the 10v source cannot and will not affect the running circuit of lights by dialing it to any voltage possible, yet the 7.4v does. Dialing the 7.4v up they blow, down they dim like supposed. - nforystek
