The windmill has an 8-foot prop attached to a converted 3-phase motor.  The motor was a 3 horsepower industrial motor.  After putting the permanent magnets on it I experimented with 12 volts, but I'm getting more power now that I can operate at 24V.  Over the summer (when there isn't much wind anyway), I disassembled much of my battery and control systems.  I have re-installed the Xantrex C40 controller (now it has a lightning arrester).  The battery bank is a discarded set of GNB Absolyte cells, which are good enough for my purposes, but they do show their age.  At 24V there is about 800 A-hr of name-plate capacity, but considering their age, my desire to not discharge below 50%, and winter temperatures in the shed, I only want to use about 2-300 A-hr before a re-charge.  Converting that into watts and accounting for inverter's efficiency I'd like to think I have 4000 Watt-hours available.

Power is drawn from the batteries by a Xantrex 4024 inverter, bought used from another forum member.  (Chad if you're out there, I'm very happy with it, thanks again)  The inverter is hard wired to a circuit-breaker box with a 30A feed to the barn.  The underground wire could accommodate 240V if I need to in the future, but for now there's only one phase of 120V because that's all the inverter will give me.  (nb: if I were to step up to 240V, then the service would be de-rated to 15 or 20 Amps, otherwise the inverter would burn up before the breaker trips).

At this point, only one electrical outlet and a small overhead incandescent is attached in the barn.  I will be putting a more permanent pair of fluorescents in the roof this weekend (four 32W energy saver bulbs = 120W).

As I also pointed out, there are lights in the other shed and a yard light.  The yard light uses about 300W but it's on a timer and a daylight sensor and only on when the switch is turned on.  That plus the other bulb add up to about 400W.

So if I've done my math right, the battery system can provide power to the all of these lights for about 7 hours.  If we need them all on for an hour or so every day while doing chores, then about a week can go by without a wind to provide a recharge.  That may or may not be cutting it close.

If it's not enough, I'll probably find out in December.  If it is enough to make the system work, then I won't be sure until April.