Yeah, I think running a 12v system, with a 40A (520 watt) controller, I am going to be ok. Still on the fence about a 40 or a 60, but that is really no big deal.
My desired load to cover is about 10.5kw per day (10,400 watts, a 1300 watt load for 8 hrs a day) (actually 1260 watts and maybe 8 hrs a day or 10,080 a day, but I like to estimate a little high that should cover some of the start up current) . 10,500 + 24 hrs means I need to make about 438 watts per hr.
I have no idea on battery bank size just yet as the load is actually 3 loads that run sometimes and sometimes do not. A fridge, a freezer and the furnace. I am not looking for reserve power, but just enough that it can catch back up charging between all the things kicking on and off.
I had this idea to just kick the furnace fan back to grid power when battery voltage got about halfway discharged, but decided to just have them all (the entire load) kick back to grid power if the batteries get discharged.
I am not so worried about back up time, as I have a generator if the grid power goes out anyway. I am more after keeping said load off the grid, when I have the wind to do it (avg wind here is 15 mph). So pretty much all the time, except the rare days when we do not have much wind.
I am also thinking that while I am going to build a well insulated battery box, it gets really cold in the garage where the batteries are going to be. 0 degrees F for sure during the winter ( I eventually want to solve that by insulating the shop). So I might need to think about battery pads and that is going to use power. Maybe not, maybe the charge discharge of the batteries will warm up the inside of the box enough, I just do not know yet. Plan for the worst type thing.
So in my experience so far..... I should be ok as far as my payback time frame goal. But I really have to wonder if I would not have been better of buying a small wind turbine and calling it a day. That has crossed my mind, but I do not think I can buy one that puts out what I think the one I am building will at low wind speeds ( as consistently is a better way to say it). Remember, my goal was to just have a mill that just chugged along putting out a decent wattage and voltage almost all the time. While I may not be able to put out quite the voltage I wanted and thus have to go to a 12v system, I am still thinking that I can win this race if I can just chug along putting out 500 watts almost all the time. I think that is very attainable. With MagnetJuices calculations, that means I need to be at about 110 rpm (or a bit faster) as much as possible. Especially when the wind is 12-15 (avg) mph and while it is under load.
I have high hopes it all goes pretty well, because it has been a great learning experience and I am already thinking "the next one I would change this". Lol. Thanks for all the help guys, because I am quite certain that I would not have done what I set out to do without your help.