How to measure voltage of three different batteries

[BlueG]

Q1. Because gnd are no seperate, you must interconnect bateries
Q2. wcs1800 has max DC current to 35A, if you have 60 you must find another sensor. We can add its support to Lk
Q3. Actualy now, you have 6 analog inputs. You may rebuild PCB and use VCC  inputs.

Thank you