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Solar basics

 
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I looked through the electrical forum topics and didn't find a relevant heading so I apologize if this is a redundant, oft answered, question.

Was there (or is there) a purpose in having multiple options for system voltage (I.E. 12, 24, 36, 48, volt battery banks) or was this a mere offshoot of backyard experiments or corporate efforts at non compatibility to encourage in house systems?

Is there any advantage of higher voltage DC systems, given comparable wattage?
 
gardener
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Location: N.E.Ohio 5b6a
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We like 12v dc because it will not shock you.  You can put positive and negative in a chicken waterer and nothing will happen.   It is safe around the kids as long as it is fused properly.  It will weld if it is direct shorted and enough amps are available. We use 12v to run corn shellers and grinders, coolers, heaters, fans, fence chargers, and a fridge.  The reason for upping the voltage is to use smaller wire for the same given power. Amps x volts + watts.  Amps make for bigger wire.  12v x 1a=12w, 24v x .5a=12w.  36 volts starts to shock you on hot sweaty days and 48v will bite you harder.  You can think of it as volts = how hard it pushes and amps = is how much it is flowing.  
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So using more smaller systems the 12 volt is better?  If you are not trying to push the voltage a long distance then having more but smaller independent systems may be worthwhile if you are scaling up an operations.  Is that about it?
 
master gardener
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While there are strong efficiency arguments in favor of higher voltage systems, I chose to go with a 12 volt system due to safety concerns.  I have no idea as to why there would be multiple voltages .....unless ....maybe....the individual had multiple DC appliances running off different voltages.  I chose to convert to standard AC because I already had the appliances, and DC appliances often cost a fortune.  The energy lost in the conversion could be made up by adding a couple more batteries and panels.

The cost of wiring was also a concern for me.  I live in a very shaded house. My panels are a good distance from my house.

Oh yes, another reason I have for 12 volt is that if I should decide to run with DC  appliances, many of those can be found at a truck stop.
 
Rocket Scientist
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Hi Bill;   For the most part it is solar power just evolving from its roots.
I have been 100% off grid since 1983... I've seen a lot of changes.
I still make my power as 12 vt and then invert it to 110.   Using a pure sine wave inverter produces cleaner power than the power company can make.

The military started using 24 volt systems to utilize smaller wire that can run longer distance.
The solar folks picked up on that and started using 24 volt over 12.   Its just easier to move DC voltage @ higher voltage.
Hence came the 48 volt systems.  The old theory if a little is good then a lot must be better.

Enter the grid intertie  systems and mppt charge controls.  Now you started seeing 36 volt panels, that could be located quite a distance from the battery's .,
Power is generated and transmitted at a high voltage.  Mppt charge control systems bring that voltage down to your system size,  or sent down the power lines to the grid.

I do have a small straight 12 vt system in the house that gets used all the time as lighting.  The rest of my home is all inverted power.  Its too easy to buy anything you want or need at 110, 12 vt stuff is readily available @ truck stops and marina's.  But the cost is unacceptable.  
 
John F Dean
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Hi Denny,

I hesitate to use the word better. Certainly better for me.  There are many people who would encourage a 48 volt system.
 
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looking for some options opinions to get the most out of my setup.
I have:
3 100w mono solar panels wired parelell
6   12v  100AH deep cycle batteries
40A mppt charge controller
Load wired directly to my camper 12v system
3000w sine inverter for AC outlets

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pollinator
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Location: Massachusetts, Zone:6/7 AHS:4 GDD:3000 Rainfall:48in even Soil:SandyLoam pH6 Flat
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Higher Voltage means higher available power. Most devices (charge controller, inverter, charger, breakers, etc) can only handle around 150A. (One can always pay a higher though)

So a 12volt x 150A = 1,800W
vs
48volt x 150A = 7,200W

Voltage above 48 will shock you, so 12v and 24volt are wonderful low voltage options.
Higher voltage means less power loss in the same size wire, thus enabling a longer cable run, or smaller wire for the same length thus saving money.

24V is wonderful for alot of off-grid direct drive pump, fridge and freezers.

I like 48v because that is the same voltage that Power over Ethernet (phones, computers, wifi/network devices, lights, USB-C Power Delivery), and each cable can deliver up to 100W.

120V DC is popular for direct drive workshop machines (circular saw/etc)
24v and 48v cordless power tools can also be ran directly too


 
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