I'm spending more time than I ever imagined getting a DC-DC converter to work. I bought a good one too - Meanwell 200 watt converter. Remy - I don't follow your logic in requiring having a fancy L-A battery charger. Car alternators have been doing an acceptable job for years, and they are constant voltage chargers at or near 13.6 V or so. The newer solid state regulators might trim that voltage based on ambient temperature as a proxy for the battery temperature, IDK. And beyond that, we aren't using them to crank a starter for an ICE. An even better solution would be to toss the 12 volt battery and use a supercapacitor. But my Miata's 12 volt system has very low power requirements.