Hi, Steiner

The problem will be to find circuits ( Multiplexers, Comparators, AOPs ... ) that can bear 72 v on their inputs.
For Li-ion or Li-PO, a good precision has to be kept, so voltage dividers have to be forgotten ...

A solution could be to use a simple V / F or V / PWM converter ( low end PiC ... i.e.) connected to each cell, and opto couplers to enter the info into your main controller ...

Alain