12V DC to 12/24V AC

[ars3]

Hello,
Does anyone know how I can convert 12V DC to 12 or 24V AC?
I'm a novice and have been looking for an alternator to buy but haven't found any.

I'm trying to do the following:

I have a house that's completely off-grid. I have 10 12V heavy duty forklift batteries. I have a 12/24V - 240V 8 KVA transfomer.

I need to feed the transformer 12 or 24V AC from the battery bank.

I hoping to eventually power the whole house. I have a need to produce enough electricity to power a 220V 30amp central AC system.
This is not my permanent residence and will be used only on weekends etc..

I am recharging the batteries with a 90 watt solar panel.

I would really appreciate any help.

Thanks,
Andrew

 

[williB]

i think what you are looking for is an Inverter system which convert 12V-24V DC to AC..
try googling Inverter system

 

[stevez]

They do make commercial/industrial inverters that will handle the load and will provide reliable service. As you might expect, they won't be inexpensive. As expensive as they might be that still might be economical relative to other options.

Have you done the math to see how long you can actually run your power system? I can imagine fork truck batteries that are no larger than auto batteries - but have seen plenty that are as large as an auto (almost!!).

90 watts x 7 days x 24 hrs/day is 15,120 watt-hours. 220 vac x 30 amps is 6,600 watts - or a little more than 2 hrs run time. The solar panel won't put out 90 watts continuously so you aren't going to get much run time unless you have a supplemental charging system. The math isn't precise but it gets you thinking about the order of magnitude.

There are absorption type refrigeration systems that are used in RV refrigerators. They use heat and an ammonia cycle - the heat coming from resistive element. It's not particularly efficient but it works. If you could provide the bulk of cooling that way then a common, low cost invertor could run the evaporator fan and other appliances. I'd like to think that someone makes a residential version.

Sorry it's not a schematic but I hope to have been of some help. Good luck.

 

[Nigel Goodwin]

90 watts x 7 days x 24 hrs/day is 15,120 watt-hours. 220 vac x 30 amps is 6,600 watts - or a little more than 2 hrs run time. The solar panel won't put out 90 watts continuously.

Obvious flaw here is expecting 24 hour continuous sunlight :lol:

Another problem is the 90W spec of the panel, this is very likely to be the theoretical absolute maximum possible - as I always say, 'think sahara desert at noon!'. Under normal sunny day conditions I suspect you would be lucky to get 8 hours averaging 45 watts?.

 

[stevez]

As must be obvious, some of us tend to step back and try to see the whole picture then link things together - often using oversimplifications or based on a perfect component (the 90 watt panel for example). If the 'perfect' plan looks like it will work it might then be appropriate to move on to the details. My physics professor used to keep hollering "F equals M A" to get us to think in those terms. What goes in has to match what comes out - it has to balance. It took about 20 more years for that to sink in and stick.

My electronics professor (I'm an ME) use to holler about PBCs - Pink Brain Cells and the adverse effects of alcohol. Had nothing to do with electronics but everything to do with our lives- especially then. The man was also color blind which explained his odd clothing selection but not how he managed the resistor color code. I have to say he's at the top of my list of people I admire.

 

[bryan1]

Hiya Stevez,
Don't bother with a 12-24 volt step up converter, just get another solar panel and hook up up in series so you get 24 volts. If your transformer (inverter) will handle 24 volts it's the way to go but make sure you have a solar regulator and a decent fuse in the system. Another forum where you can get a heap of info on alternate power is www.otherpower.com . Take a look thru their site and you'll find a forum there aswell.

Hope this helps Bryan