A small correction, if you don't mind... 3.7V batteries actually charge up to and are running around 4.2V unloaded. The loaded voltage on a 3.7V MOD with a freshly charged battery is 3.9+ V (depending on your atty resistance), but does start dropping as the battery's charge drops. The nice thing about the ProVari is that it will provide consistent performance until the battery needs to be charged regardless of which volt setting you choose.