best cost effective batteries?

[foolioGrimz]

hi im new to wind power. im doing some research on power systems. Im planning on experimenting with the homebrew windmill. I had no idea copper wire was so expensive until I started researching this.    What im shooting for is running my 6,300 btu window ac and a flurescent lamp off the grid. I was using the central air but that was running 3-400 a month down here in south tex. not sure if the cost of batteries would outwiegh having it off the grid or not. But I like to take on weird projects like this for fun anyways. I work alot and only use power for 8-10 hrs max a day now. what kind of batteries would be the most suitable? how would some refurb. 12v deepcycle work out? they might be the cheapest to get ahold of

[Tritium]

It  cost more to make your own power than to buy it from the grid if you already have a grid connection.

Thurmond

[ghurd]

6300BTU A/C?  Yikes.
I am guessing that's running about 5A at 115V, which is about 50A at 12V.
If you think CU is expensive, wait until you calculate the battery required in a reasonably designed RE system.

The florescent lamp is nothing compared to the A/C.

Need to rethink power.
"I work alot and only use power for 8-10 hrs max a day now."
10 hours x 31 days = 310 hours max.
"running 3-400 a month"
$350 average.
That's near $0.50 worth of grid per hour, or maybe 3000W continuous 24/7?

Need to rethink how that power is used.
Time for more insulation, turning the temp up, programmable thermostat, white curtains on the windows, CFLs, turn the water heater down, attic fan, etc.
G-

[foolioGrimz]

ya, I figured it would run a few bucks to set up. Im going to have a few grand to throw around soon.  I need something to do on my days off so i dont go crazy lol.  I wonder how the power output is different between the 12, 24, and 48 volt configurations are on the 10ft homebrew.  I was looking up forklift batteries and they cost a bit, and I would have no idea where to get them. I doubt UPS would be happy if I ordered one of those. lol golf cart batteries or deep cycle would be the easiest to get ahold of. 

[frackers]

Just work it out from dollars per watt hour.

A golf cart battery is usually 225 amp-hours at 6v which is 1350 watt hours. Where I am they are $300 so you're looking at 4.5 watt-hours per dollar or 22c per watt hour

Note this is the cost - not the size. Any sort of lead acid battery, even a 'deep cycle' battery I wouldn't discharge below 50% so the effective power available is 675 watt-hours which effectively doubles the price to 44c per watt hour.

So you want to run the AC for 10 hours when there is no wind. Assume it takes 5A at 155v as per Ghurds figures then you'll want 5 * 115 * 10 of battery _AVAILABLE_ power - 5750 watt hours. Thats going to cost $2530. And that is just the battery cost assume 100% efficiency in getting 115v from your inverter.

I guess you can buy a LOT of grid power for that.

As for system voltage, if you're looking at 575 watts then that is 48amps at 12v, 24amps at 24v or 12amps at 48v. In this case I'd go for 24v as inverters and stuff are cheaper than at 48v and the 12v option means really thick cables to carry the current (and the attendant losses).