Determining the voltage of 5 phase PMSM motor
Determine the voltage based on what? On the geometric parameters?
You would have to define what do you want to optimize: power? efficiency? cost? space? To keep things simple I would pick an standard voltage level. In your case I would pick 110 V (You still need a DC/DC regulator between battery and machine)


The best book about electric machine design that I know if is in german: "Berechnung elektrischer Maschinen" (https://www.wiley-vch.de/de/fachgebiete/naturwissenschaften/physik-11ph/elektrizitaetslehre-11pha/berechnung-elektrischer-maschinen-978-3-527-40525-1). In english I like "Design of Rotating Electrical Machines" (https://www.wiley.com/en-us/Design+of+Rotating+Electrical+Machines%2C+2nd+Edition-p-9781118581575)