Alternator rewiring from Isolator to Orion XS DC-DC

Hello,

I am re-wiring sailboat, removing battery isolator which had special “R” terminal with the small wire going to Yanmar Hitachi alternator. This wire sends battery voltage at small current to alternator’s “energiser” terminal without which alternator does not start creating current. Alternator is wired to AGM starter battery, and then from AGM via DC-DC charger to lithium house bank.

Question - where should I get “source” for that wire going into alternator? Directly from AGM battery, from Victrons “remote” connection, from ignition switch or? Does it have to be fused?

Have tested connecting directly to battery and it works, but afraid I may be missing something.