Great question — answering as the UphillTech team:
By sizing the loads appropriately Every load has a nameplate or published draw. You are to use the numbers on the various nameplates to assure that you are not overloading the circuit, or (more literally to Code), to assure you provide large enough circuit(s) for your loads. You can get any ampacity of battery charger that you want. You seem to be looking for an electronic solution; that's grossly over-complicated compared to simply sizing circuits (or appliances) correctly in the first place. But it is permitted in Code, mainly used for "load shedding" to allow an automatic transfer switch with a generator that is too small to pick up all provisioned loads. You couldn't use that gear here...
Full answer by Harper - Reinstate Monica: https://diy.stackexchange.com/a/223523 (CC BY-SA 4.0).
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