But it's not, really. At the very least, the system voltage matters to every power-handling component. You can't just swap a nominally 48 volt battery with a nominally 360 volt battery like nothing else (such as the controller) will care. I do agree that once an operating voltage range is established, components can be changed individually to a significant extent.One of the nice things about EV builds is that your setup is modular and agnostic to the rest of the system. If you want to add battery capacity later, you can. If you want to upgrade the speed control, you can. If you want to upgrade the dash, you can.