Sorry, but I have stopped coming here frequently, so did not see your post before today. Send me a brief email next time so I know.
My calculations were based on this calculator. If you have a 100 AH battery and you run 3 fans of 70 W each, then the total run time would be 2.3 hrs. Meaning your battery will drain to zero after 2.3 hrs, unlikely in real world as homage inverter will shut down when your battery reaches 20% charge-left stage.
So, from the calculator, if you run 3 fans for one hour then your battery is almost 50% drained. At 10 A/h charge rate, technically it should take 5 hrs for your battery to charge back to 100%, however in real world, rate of charging depends on many other factors, so all you can calculate is an approximate figure. For your specific case you can calculate the time homage takes to charge your battery after one hr use.
I hope I answered your questions...