I’m working on an electric vehicle project which will have 20 Lithium batteries in series making a total of 74 volts. I need to be able to accurately measure (8bit or higher) the voltage of each cell and this is where I hit problems. Most ADC modules have a common ground, fine when you connect to the first cell, but when you connect the second, the common ground shorts out the first battery and so on. I’ve looked at isolated ADC’s and again there are limitations as to how high a voltage can be connected, most I’ve seen are able to float at around 36v and no higher. I’m not a very good programmer and I want to avoid the more expensive fancy devices with no library support.
I have considered another approach which in its basic form is to add a potential divider circuit with protection to each ADC input, the potential divider would consist of simply a multiturn precision wire wound preset, and my question is, would this be stable and accurate enough?