In the app: Battery→Cells
From the guide: What some readings mean
Cell spread (highest minus lowest cell voltage): under 60 mV is normal (the app's threshold); it naturally widens near empty and full and under heavy load. A spread that keeps growing over weeks is worth a shop check.
From the guide: Battery tab
Cells: highest, average and lowest cell voltage and the spread. Under 60 mV is normal; a spread that keeps growing over weeks is worth a shop check.