For use cases where there is no "Starter" batt on input, if the input current will always be sufficient to carry the loads on the output side, then the only need for a battery there is that buffering function.
The real question is
will the DCDC potentially be harmed by a stock alt setup's "dirty output" if that input side circuit contains no battery at all?
Discussions with Charles and Sterling TS imply that may well be the case, not necessarily immediate damage, but possibly reducing the unit's reliability or service life.
A small cheap lead battery would suffice in this scenario.
But perhaps the Victron is designed with better input filtering so that it is not required at all.
I suppose without clear direction - the VR involved may be the determining factor - it is better to follow convention and always attach input to a battery's posts.
When currents pulled by the loads on the output side may peak higher than the input energy source then a decently sized battery there is important as a "time shifting window" storage buffer anyway.
But allowing the unit to continue to draw power from the input-side bank without any real source actively contributing enough current would very rarely be a sensible design.
The real question is
will the DCDC potentially be harmed by a stock alt setup's "dirty output" if that input side circuit contains no battery at all?
Discussions with Charles and Sterling TS imply that may well be the case, not necessarily immediate damage, but possibly reducing the unit's reliability or service life.
A small cheap lead battery would suffice in this scenario.
But perhaps the Victron is designed with better input filtering so that it is not required at all.
I suppose without clear direction - the VR involved may be the determining factor - it is better to follow convention and always attach input to a battery's posts.
When currents pulled by the loads on the output side may peak higher than the input energy source then a decently sized battery there is important as a "time shifting window" storage buffer anyway.
But allowing the unit to continue to draw power from the input-side bank without any real source actively contributing enough current would very rarely be a sensible design.
