12DC to 12/24AC

[(unknown)]

Hello,

I am trying to power a house in a cattle ranch that's off-grid.

I have a bank of 10 12v batteries, 6 45watt solar panels and I also have a 12/24vAC-to-110-220VAC 8KVA transformer.

My problem is how to do I got from the 12vDC to the 12v or 24V AC? I cannot find an inverter or converter that can just convert DC to AC on the same voltage.

Does anyone have any ideas?

Any help would be appreciated.

Thanks,

Andrew

[ghurd]

Hi Andrew,

You would probably be much better off buying a inverter.

Many reasons why,

my favorites are cheaper, easier, and more efficient.

G-

[joelhacker]

Tis True...Remember by Ohm's power law W=V*A that you must

have significant amperage to drive a transformer (especially

if it is 50Hz) at 12 volts to get any significan power at

120 volts.

Remember that it is a 10x increase in current, and the

drive circuitry at lets say 150Amps @ 12VDC is quite

heavy, produces a lot of heat and is quite expensive

to make, and will only give you 15 Amps Household 120 VAC

assuming no losses...

Commercial Inverters are best :-)

[drdongle]

Guys are right, save your self some head akes and get just get a 12VDC to 120 VAC inverter.

[(unknown)]

Thank you for the comments... From what I gather the transformer idea is bad; therefore, I will pursue the inverter.

Are there inverters that can take me from 12vDC to 110/220vAC?

Also, do you think I get better use of 48V batteries or 12V batteries? I have several 24 and 48 batteries and can always get more as the price to use is not too much different. I just have more of the 12V.

Ideally, I would like to power a 220V 30amp machine we have at the ranch but haven't yet been able to find an inverter or transformer that can do that for me.

Currently, I use a gas generator for that machine.

Any ideas?

Thanks,

Andrew

[alcul8r]

<Are there inverters that can take me from 12vDC to 110/220vAC?>  

Yes

<Any ideas?>

Yes, but we'd need an idea of how much power you realistically want to store and have available.  If all you normally need is a few lights and a radio, keep it 12 volts.

<Ideally, I would like to power a 220V 30amp machine we have at the ranch but haven't yet been able to find an inverter or transformer that can do that for me.<p>
Currently, I use a gas generator for that machine.>

If you are considering getting a significant part of your power form the PV panels, forget the heavy draw machine.  Even if you had 100% efficiency, the panels would have to pump juice into the batteries for more than 24 hours to run it for one hour. In practice, you only receive limited sunshine each day, and overall system efficiency will be closer to 50% than 100 after taking all the losses into account.

<Also, do you think I get better use of 48V batteries or 12V batteries? I have several 24 and 48 batteries and can always get more as the price to use is not too much different. I just have more of the 12V.>

What else do you want to do with the electricity?  Your 270 watts of solar is adequate for only a few lights or so.  If you want much more you might have to charge the batteries while the generator is going to run your big machine.  There are modified square wave inverters which will do 2000 watts off 12 volts, but I think for anything bigger than a few hundred watts I would go to 24 volts or bigger.

If you are not a big power hog you can run stuff up to a smaller microwave on what you have with just the addition of an inverter.

Have fun,

Rex

[ghurd]

I agree with Rex.

Use gas for the 220V 30A machine.

The 270W of PVs is great for lights etc,

but not for a 9HP machine.

G-

[(unknown)]

I have a house at the ranch with 15watt lights that we currently power with a little bank of 12v batteries. We just take those home every time they drain and recharge them at home with a 110 charger.

However, we have a 220V 30amp Compressor at the ranch that we power with a gas generator. We only run it a few hours a week. Mostly when we need to get air to the tractors or work on other equipment as we have pneumatic tools.

At the ranch house we also have a refrigerator that we power with the compressor from time to time. It a 110V 15amp draw. We would like to have it on all the time.

Lights and the such is quite minimal as we have plenty of windows and go to sleep early.

My main concern is the 220v 30amp compressor. I was also thinking of getting a central AC system to the house but I know that's also 220 with at least 20am draw.

I am open to using something other than PV such as wind.

I apologize but this is all new to me as we've always used the gas generator but since we built the house, we've had to experiment with the batteries and I don't know much about this just yet.

Thanks,

Anderw

[Bryan1]

Hiya Andrew,

            Good to see you found the forum. On the subject of your compressor an induction motor will draw up to 10 times the current on startup so forget the idea of trying to use alternate power for the compressor. Another option could be adapt the compressor to be driven from the pto of a tractor. The only other option I can think of is go back 100 years and build a steam engine to run it, sounds wacky but it is feasable if you have the fuel ie: plenty of wood.

Cheers Bryan

[wdyasq]

Andrew,

You might want to check this out:

http://mtbest.net/chest_fridge.html

If the claimed "100 watt hours a day" is correct, a 20W solar panel would supply what one needed.  40W-80W panels would supply more than enough for lights and refrigferator.

Of course one would need batteries and inverter.  In such a small system, I doubt a charge controller would be needed if the batteries were sized right.

Ron