Can I Get 120v From a 12v Battery

BernieM

Living in a remote desert location, I take to generate my own ability from solar. Big loads require big inverters, and for me sine moving ridge is a must, not modifieed sine. College voltage inverters let more batteries in a string meaning more storrage capacity in that cord and since multiple parallel strings don't accuse well, a large capacity unmarried battery or cord is better than smaller parallel arrays.

Large sine moving ridge inverters are expensive. So while considering the problem, I hit upon what at offset glance seems to be a simple and effective solution. Namely, put sufficient batteries in series to reach the desired a/c voltage and then using a simple and inexpensive waveform generator, drive a large power transistor or series of them to provide the wattage chapters desired. It should exist make clean enough equally far as power goes to exist usable without much waveform conditioning I would think.

With 12 volt batteries, for example, 10 of them when fully charged will be at 126 volts and when tuckered still be at 108 volts, nearly 110 volts, though ane wouldn't desire to let them get that far drained. Probably cut out when they reach 11.2 volts or so, or 112 volts on a chain of ten. With my 24 volt inverter, the maximum number of 12 volt batteries I tin put in a string is ii, with half dozen volt batteries, 4. With this method I can utilise 10 12 volt batteries or 20 vi volt!

OK then what am I missing? I get a sneaking suspicion that someone is going to mention the down sidde that I'm overlooking. Ok so have at it! Is this a expert solid solution or should it exist filed in file 13?

nsaspook · Mar 28, 2015

Lets start with a very simplistic circuit.
First to generate a good sine wave directly from the batteries the total voltage will need to be 2* the elevation voltage of the output Air conditioning waveform. You then demand to isolate the DC boilerplate voltage from the Ac voltage with a big capacitor to get that pure Air conditioning sine wave output. This ways using a class A ability circuit.

It might work but volition be very inefficient unless y'all also demand a space heater.

x86

Beginner applied science student here. Have you thought well-nigh electric current?

Wouldn't a 120V supply supply unlike current than the electric current from a 12 volt supply?

phinds

Beginner applied science student hither. Take yous thought about current?
Wouldn't a 120V supply supply dissimilar current than the current from a 12 volt supply?

Yes, but so what? What'southward your point? The actual current fatigued depends on the voltage source and the load.

BernieM · Mar 28, 2015

Potential is at 120 volts already, ten 12 volt batteries in series, for example. Simply turning an scr on and off 120 times per 2d reversing polarity every other on bicycle gives me a 60 hz square moving ridge, which is what a lot of cheap inverters actually produce. Seems a unproblematic capacitance circuit might shape the square wave into the sine. Or maybe someone makes a cheap foursquare wave to sine moving ridge converter. I mentioned the power transisttors or maybe ability FETs as just a way to make the low ability of my inexpensive waveform generator output the power every bit a sine wave. In other words use the depression ability sine moving ridge generator to drive the base of the transistor. The load volition decide the current drawn through the transistor or whatever.

phinds

Potential is at 120 volts already, 10 12 volt batteries in series, for example. Merely turning an scr on and off 120 times per second reversing polarity every other on cycle gives me a 60 hz square moving ridge, which is what a lot of cheap inverters actually produce. Seems a simple capacitance excursion might shape the square wave into the sine. Or maybe someone makes a cheap foursquare moving ridge to sine wave converter. I mentioned the power transisttors or maybe ability FETs as just a mode to make the low power of my cheap waveform generator output the ability equally a sine moving ridge. In other words use the low power sine moving ridge generator to drive the base of the transistor. The load volition make up one's mind the current fatigued through the transistor or whatsoever.

This method volition not produce what is normally hateful by "120V" because that is an RMS value whereas you are talking most peak value. Reread nsaspook's post #2

BernieM

Lamentable I was thinking about 240 when I was writing 120. 120 is 60 volts peak, 120 volts meridian to peak. But that'southward fine and so 240 volts a/c from the 10 batteries. I judge I am most interested if there is a relatively simple way to exercise this that isn't too ineffficient. No I don't demand a infinite heater in the summer in Arizona.

phinds

Sad I was thinking about 240 when I was writing 120. 120 is threescore volts summit, 120 volts height to peak. But that's fine then 240 volts a/c from the 10 batteries. I guess I am most interested if there is a relatively simple manner to do this that isn't too ineffficient. No I don't need a space heater in the summer in Arizona.

You demand to check your math.

nsaspook

I guess I am most interested if there is a relatively simple way to do this that isn't also ineffficient. No I don't need a space heater in the summertime in Arizona.

There really is no efficient way to direct generate the sine wave directly from bombardment voltage. Using a push button-pull transformer solves the 2* peak voltage problem but if you stick with direct analog generation for the pure sine moving ridge you will be stuck at <50% efficiency. A efficient device is a circuitous device every bit this project demonstrates.

https://www.wpi.edu/Pubs/E-projection/Available/Due east-projection-042507-092653/unrestricted/MQP_D_1_2.pdf

ibuildstuff

Uncomplicated manner to become effectually the RMS vs. peak voltage problem: add iv more batteries. That brings yous to a total of 168 volts, which is really shut to 170 volts, which is the meridian voltage out of your standard 120 volt wall socket. With that out of the style, the just other trouble I encounter with this is that yous're assuming the transistors will behave in a completely linear manner in response to switching voltage. I have no idea if that's true, but I doubt it. You ameliorate check that out before you blow some appliance up with a malformed waveform.

jim hardy · Mar 29, 2015

Big loads require large inverters, and for me sine moving ridge is a must, non modifieed sine.

i dont know of any household appliances that are picky about sinewave purity.
What is your thinking?
I've seen a square wave inverter with just a 3rd harmonic filter, a brute force Fifty-C series resonant excursion tuned to 180 hz , merely the waveform is still crude...

Mr Spook'south link is a virtually interesting approach . I never saw that triangle moving ridge - comparator trick earlier in that application.

Another method is here...
http://world wide web.tinaja.com/glib/msinexec.pdf
sort of a a twist on Fourier
synthesize a sinewave equally a sum of square wave harmonics

old jim

Jobrag

How big are your loads and why do you need such a make clean voltage, (your non Blofeld setting up a secret base are you). Have you considered an MG setup?

sophiecentaur

for me sine wave is a must, non modifieed sine.

This is a statement that I have to question. What is so special virtually a 'pure' sine wave? If yous consider that 'the Mains' would do your your purpose then I advise you look at the actual waveform the supply company gets to your business firm. Information technology is only, always, a crude approximation to a sine wave and information technology varies every bit other loads are added and removed. And then, if you reconsidered your requirement, life could be a lot easier.
Alternatively, you lot could perhaps modify the equipment yous are supplying with the 120V AC and make information technology less fussy. That could be a much easier style through this problem of yours.

sophiecentaur

Yo which particular bit of that wide ranging reference were you wanting to draw attention?

rollingstein

i dont know of any household appliances that are picky near sinewave purity.

Practice motors run hotter? I thought they did. Non sure.

Svein

Yo which particular fleck of that broad ranging reference were you wanting to draw attention?

I simply wanted to describe attending to it. I am repeatedly getting warnings for being too close to the answers...

Chacabucogod

What about using a Boost Converter or a cascade of these to get your voltage really high? Then build the inverter.

sophiecentaur

I merely wanted to draw attention to it. I am repeatedly getting warnings for being too shut to the answers...

A few words to help direct the reader to the appropriate section can help without 'giving abroad' anything. Only, in any instance, it was not a homework type question so it deserves loads of helpful answers.

Practice motors run hotter? I thought they did. Not sure.

Peradventure, only that's no reason to have to produce a 'perfect' sine wave. (How perfect does that hateful, in any case?)
I asked the question about required quality of sine wave because information technology is the start thing an Engineer should do - i.e. ascertain the specific problem rather than come in half way through with an answer that takes ones fancy.

sophiecentaur

What near using a Boost Converter or a cascade of these to go your voltage really high? Then build the inverter.

What would be the point of changing the input DC voltage when a transformer will do the job (probably) cheaper and more efficiently, once y'all have your Ac?

rollingstein

Possibly, only that'due south no reason to accept to produce a 'perfect' sine wave. (How perfect does that mean, in whatever example?)

Agreed.

I faintly remember a vendor trying to sell us some system to improve the harmonic quality. Is that like to going closer to the "perfect" sine wave?

Every bit far as I remember the argument was that fifty-fifty at the aforementioned power factor rotating machinery would operate better ( cooler?) with a better harmonic construction.

Could have been snake oil.

sophiecentaur

Could have been snake oil.

Oil in a bottle with no numbers on the side is probably snake oil, for an Engineer. The Ability factor affair may or may not be a real consideration here.
The OP may not exist referring to motors and efficiency. It would be nice to know the actual numbers involved in his particular requirement. I suspect that the bodily requirement hasn't been specified quantitatively and the notion of a pure sine wave may be a lot less important hither than he assumes.

sophiecentaur

We lost the OP somewhere along the way. Nosotros are now anchorless and the conversation has no direction to go in. There is no solution to this unspecified problem.

ibuildstuff

We lost the OP somewhere along the style. We are now anchorless and the conversation has no direction to go in. In that location is no solution to this unspecified problem.

Seeing as how no one actually told him what was wrong with his idea, instead opting to ask him the same questions over and over about sine wave purity, I'd say he's busy building a setup according to his original thought. Seriously, what else did you guys need to know about the trouble that he didn't say in his original mail?

sophiecentaur

Seeing equally how no one really told him what was wrong with his idea, instead opting to ask him the same questions over and over well-nigh sine moving ridge purity, I'd say he's busy building a setup according to his original idea. Seriously, what else did you guys need to know about the problem that he didn't say in his original post?

We demand to know his actual requirement. What would be so special about his equipment that would need a clean (unspecified how clean) sine wave supply? That question surely needs to be answered before whatsoever solution can be reached. In that location are diverse levels of power, purity and cost and why not permit us know what's really required? There are some central problems here. Do you not appreciate that?

jim hardy

Seeing as how no one actually told him what was wrong with his idea, instead opting to ask him the same questions over and over about sine wave purity, I'd say he'due south busy building a setup according to his original idea. Seriously, what else did you guys need to know almost the trouble that he didn't say in his original postal service?

How much power he wanted, for starters. His linear approach is practical for maybe fifty watts. I've used it to make three phase 120VAC in examination equipment.

I for one took this mail service every bit evidence of defoliation:

Sorry I was thinking about 240 when I was writing 120. 120 is threescore volts peak, 120 volts superlative to elevation. But that'south fine then 240 volts a/c from the ten batteries. I guess I am near interested if there is a relatively simple manner to practise this that isn't too ineffficient. No I don't need a space heater in the summer in Arizona.

With a single 120 volt supply and simple linear amplifiers every bit he proposed, you can just make 84 volts RMS at maybe 30% efficiency.

Since he doesn't appear familiar with sinewaves i asked why he felt he needed one.