Interesting question.
Have you actually confirmed there is no power going to the macerator? It could be a jammed or failed macerator. With power confirmed, to find out which batteries the macerator it is getting its power from, disconnect the house batteries and check for power again.
There is no guarantee that the macerator gets it power from the same place on every model and model year. I couldn't tell you where our 2007 macerator gets its power from, as I don't recall ever investigating that.