Measure battery bank voltages

Is it possible to take the individual analog value of a set of batteries (12 Vdc in series, example 4 batt), through voltage dividers with a single RIO?. What would be the correct connection diagram?

Yes.
I have done that and a few other customers have done that.
Two 1k ohm resistors will tap it down to a safe voltage (remember, at full charge you can see over 14.5ish volts). Just do some math in the scaling or Node-RED or in the end result to get very accurate battery voltage.
I will draw out a diagram as soon as I can, but I am not sure what you mean about 4 batteriesâ€¦ Do they all have a common ground?

Thanks for your prompt reply Ben. I think a drawing would clarify more things.

The RIO channels for analog input share a common connection internally, so you would need to measure the voltage (with a voltage divider circuit to keep it under 10VDC) with a common reference. This would nominally measure 12, 24, 36, and 48 volts on each channel.

Select high value resistors to minimize the parasitic drain on the cells, particularly because one battery will be connected to all the divider circuits and will go out of balance sooner.

Thanks for the diagram @nextcontrol very helpful.
As @philip said, all the voltage inputs on the RIO have a common ground, so you will need to bring the ground of Batt4 to the RIO only.
All the others will be voltage taps from there.

I have run some rough numbers to get you started. I have assumed a max charged battery voltage of 15v since I donâ€™t know the specs of the charger you using.
The most important thing is that you keep the max voltage going to the RIO under 10v at all times.

In my example here, I have said a max voltage of 9v into the RIO for a battery voltage of 15v on each battery.
Of course, when you hook this up check each battery tap with a meter before you connect it to the RIO.

You will need to do some math in Node-RED or your strategy or what every you are using to monitor the actual numbers.

If you want to play around with the numbers, I like this calculator here:
https://ohmslawcalculator.com/voltage-divider-calculator

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Thanks Beno and Philip, the answer is very clear