kparjun416
How accurate of a voltage measurement do you want?
35 to 80v is a reasonable range for 20 in series. 2.65 max per cell x 20 is 73v. 2.0V absolute min discharge so 40v min plus some bottom buffer.
1 volt resolution is likely enough, right?
also, when you ask for a circuit, what output do you want? A 0-5v voltage on a pin, an 8-bit parallel digital output on 8 pins? A serial output (I2c or spi or UART?), do you want an app to display it on your phone? Or a 2, 3, or 4 digit display? An LCD panel with the number? A bar graph with 40 LEDs in blocks of 10? What is a circuit in your mind?