Brricha4

Can anyone tell me if GM’s relay isolates and allows the auxiliary battery to operate in accessory mode or does it only isolate and operate the aux battery when everything is off? If so, does that only happen when the starter battery is drained a certain amount? The literature seems non-existent as to what the GM relay is actually doing. I’m trying to make this mod to operate the vehicles cigarette lighters and outlets to run camping equipment while the engine is off without depleting the starter battery. It’s not clear to me that this set up is actually doing that. Would appreciate any insight.