Hi @adurix,
Both the Pixhawk and the Navigator flight controller boards only have a single port that’s intended for battery monitoring (with one pin for current, and one pin for voltage). Both boards do technically have at least two additional ADC pins that it should be possible to manually configure as BATT2 inputs, but they’re not in the standard “power sensor port” orientation, so you’ll need to make a custom cable to be able to use them for that purpose. I believe the Pixhawk 4 has two power ports, if that’s relevant / of interest.
If you’ve got a particular flight controller and power sensor in mind then we can help provide the additional information you’ll need to configure a second battery monitor.