In short you need to read ratings and ask manufactures. There are lots of ways to figure power using current, voltage and resistance. The voltage has to be around 14 to 15 volts to charge a 12 volt battery and if you only have, say, less than one amp available, it could take days/weeks/more to charge the batteries. On the surface without knowing details, it doesn’t sound feasible and if it is, functionality should be considered, if the battery will be discharged in four hours and it takes two days to charge it, is that really something you want. You need to seriously investigate the system you are planning to build/use.