Changing the voltage settings in the ECU only effects warning for the battery low indication. A 5.0 ECU will be fine with a 2S lipo. There is the possibility to change one board in the ECU should you want to go to Kero start plugs thus making your ECU 6.0 . You can also have 5.0 ECU modified at JetCat to run 3S life and that is accomplished with the addition of a heat sink being installed on the board.