@Cruiserdrew and I have sat in camp on the Rubicon trail and monitored the Victron charge controllers on 4 other nearby rigs all while sitting in the shade under an awning drinking . I think they all had the external BT dongle. As @george_tlc says, the dongle is a short range radio module, so keep it away from the metal body of the truck and elevated and you’ll marvel at how far the connection to your phone can reach. OK, I’m chilln’ now while my batteries top off...
Well, if you can get the other guys' data while drinking some , that probably means you can change their PIN, which in turn could get you more potentially... Win-win: Entertainment and hostage ...
(Note to self: go change my PIN from default...)