Impossible to give a good answer without knowing what brand and model of converter/charger that you have.....and how many and what kind of batteries.
One alternative is to disconnect the batteries after charging them good ...maybe 3 days or so....and then plugging in and re-connecting once a month for 12 hours.
The other alternative is to disconnect the batteries and connect an external smart automatic tender type charger and just leave it connected. A 2 amp model should be fine unless you have a LOT of battery capacity.
If they are relatively new AGM types, charge good, disconnect and come back 3-4 months later.