My rig’s 12v house power system is literally divided into two sections:
essential loads - battery charging, ventilation (fans), core lighting, refrigeration, networking
nonessential (opportunity) loads - everything else: laptop charging, spot lighting, lithium battery charging, NiMH charging,
The opportunity loads run on a dedicated circuit that automagically shuts on/off with the availability of excess power. Note: in practice this almost always means excess solar power, though it could come from alternator or shore power. A bystander can hear the solenoid controlling the circuit click and alway hear/see the opportunity loads come online.
There are a few benefits to the system, but the core one is that the rig enters sundown with the batteries:
at 100% state of charge by voltage
Although often conflated, with lead-chemistry batteries those two things are not the same. A fully-charged battery will be held far above 100% SoC by voltage, and battery that was not fully charged will not offer full capacity from 100% SoC.
So here’s the data that inspired the post. The circuit has been running from about 0745 to 1905 daily, Utah time. That is 11+ hours/day where the rig has more power than it needs for essentials.