high volt EV battery 88v reading as ADC on Arduino pro mini using differential powered by isolated power supply

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Joined Mar 7, 2023
Hello team,
As per our battery & Arduino don't have common ground as we using flyback topology for isolated ground, & isolated 5v output of our flyback supply will power opam LM324, we are using as differential opam to get ADC reading on arduino.

Screenshot 2023-03-21 at 15.03.25
Screenshot 2023-03-21 at 15.03.25763×568 135 KB

so my main doubt is, do we directly need to feed battery volt to opam to use this differential circuit , can opam handle it, as i read, lm324 can handle 32 volt only.

if not, then after voltage divider only, i need to feed divider volt to this opam circuit will be the way ?

As we were suggested to use a differential amplifier by our senior mentor sir to safely give this 88v to ADC of Arduino mini. (please check in above image about the gain formula I was suggested to use, now I need help to calculate gain & hence to get a safe ADC to read this high voltage)

can you please help to give some references for calculating gain?

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