For the first cell you can have a resistor divider if max. cell voltage is above the logger 2.5V or direct connection.
Attached a schematic file which shows how the divider is connected for 4 cells. You may need to use two picologgers, to monitor more than 16 cells (for a Picolog 1216).
For each channel in picolog you need to setup-
Channel Formula (see G column xls)
Scaled Channel Reading Formula (see I column xls)
You can use ¼ watt resistors , also please use 1% tolerance resistors or better as errors multiple near the end of the resistor divider.
R2, R4 etc resistors you could use trim pots and or fix resistors in parallel to get the right value.
These resistors can be fitted to the picolog 1000's or ADC20/24 loggers own terminal boards-
PL1000 models-
https://www.picotech.com/download/manua ... -guide.pdf
ADC20/24 models-
https://www.picotech.com/download/manua ... -guide.pdf