While there may be a reason to consider polarity, voltage exists on both the positive and negative sides -it’s a loop.Found this in Maine Sail's article on installing a battery charger:
"Any terminal mounted temperature sensor also needs to be connected directly to anegative terminal, and not the positive terminal. The termperature sensor has the ability to fry the charger if connected to the + terminal and also the potential to be accidentally shorted."
While the sensor doesn't need battery voltage to operate, applying battery voltage to it is bad for the electronics on the other end.