How practical this is depends on how much power you plan to use. The inverter is 80% to 90% efficient. Assuming that you use 300 watts for an hour, the current from the battery is Ib = 300/12 + 300/12/.8 = 30 amps (I used 80% efficiency). Since the use is 30 A-H and you don't want a dead battery at the end of the hour, use a 60 A-H battery. The solar charger will have to supply 6 amps for 5 hours to recharge the battery, or 1 amp for 30 hours. Actually, since the charging process is not 100% efficient, it will take longer.