To read the 48V input on an ADC Pi you will just need to use a voltage divider to drop the voltage down to a level the ADCPi can manage.
As the ADCPi ADC chips can only read voltages up to 2.048 volts the ADCPi already uses a voltage divider consisting of a 10K and 6K8 resistor which drops the 5V input down to 2.02381V. To increase the voltage range you will just need to add another resistor in series with the input to increase the resistance of the 10K side of the voltage divider.
To work out the size of the resistor you will need to work out the maximum voltage that will be present on your battery bank and add a small margin for safety. I had a quick look at some typical charging voltages for 48V packs and it appears that they can be around 55V to 60V. A 200K resistor combined with the existing 10K resistor would give you a total resistance of 210K on the input. Using our voltage divider calculator I put in 210K for R1, 6K8 for R2 and 2.02381V for the output voltage and it gave an input voltage of 64.52382V which should be high enough for your needs.
If you add a 200K resistor in series with the input on the ADCPi you will just need to muliply the voltage reading by 12.904764 to give you the correct voltage.