i want to store power from a 15w solar panel into a capasitor that i would connect to a 12 volt battery to keep it fully charged while under load. is this possible? what size and kind of capasitor would i need.
Very difficult to do, first because you will need a very large capacitor, second because as soon as you begin to discharge the capacitor the voltage will drop, instead the battery try to keep the voltage constant, bein an electrochemical reaction.