# 12 VDC Verses Other Low Voltages



## Studhauler (Jul 30, 2011)

What are the pros and cons of 12 VDC?

What are the pros and cons of other low voltages like 48 VDC?

I imagine some of it has to do with what kind of system one is setting-up. I am not really sure what I would do or want to do, just thinking out-loud on a cold wintery day. 

One thing I would want to do is, use a low voltage circulation pump for and outdoor wood boiler, if they make such a thing.

I have no hydro, fair wind, and low solar as I live up north.


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## ||Downhome|| (Jan 12, 2009)

Main thing with low voltage is wire size.
Lower the Voltage thicker the conductor.
Coppers not cheap.


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## Studhauler (Jul 30, 2011)

I believe wire size is based on amps, a 20 amp circuit will use 12 gauge wire weather it is 12 v or 24 v or 120 VAC. The lower the voltage the more amps it will need to provide the same power.


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## JohnP (Sep 1, 2010)

12vdc is usually used for small systems and stand alone systems and as many 12vdc appliances are used as is possible. Basically items from the RV, automotive, trucker, marine marketplace. It's very safe as far as electric shock goes and by keeping everything at the same voltage, there's no loss from conversion which is only about 80-90% efficient. Also no expensive inverters.

48vdc is for larger systems or where most appliances will be 110vac. Less loss in the conversion and once converted, standard house wiring is used.

The wire size issue is mostly just from the panels to the charge controller and to the fuse/breaker box. After that it's individual circuits. All mine are 14ga and only require 2 wires, not 3 like 110vac. On my next panel purchase, I'll have to upsize my mains to 6ga. That'll be about hundred bucks. When I outgrow that I'll also be outgrowing the C40 charge controller at which point I can either wire for 24vdc thereby cutting my amps in half or to 48vdc thereby quartering the amps. Either that or buy some arc welding cables.

We've got a tiny system with a small inverter for the few things that aren't 12vdc like the TV/DVD, can opener and misc gadget chargers like cell phone, laptop etc. All lighting, fridge, fans are 12vdc. When/if I ever up my voltage to 24vdc, I'll have to convert back down to 12vdc for my lighting and fans. (fridge will run on 24vdc) Or I can switch to 48vdc, get a big inverter and just do all 110vac.


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## MichaelK! (Oct 22, 2010)

||Downhome|| said:


> Main thing with low voltage is wire size.
> Lower the Voltage thicker the conductor.
> Coppers not cheap.


The more technical explanation for this is voltage drop. The longer the wire leads, the more the voltage will drop. The thinner the wire gauge, the more the voltage will drop. The goal for most alterative energy systems is not to have voltage drop greater than 3%, which for a 12v system would be .36volts. Not much you see. So, the thickness of expensive copper wire goes up so that voltage drop is less than .36 volts. 

Put four 12V panels in series, and 4 12V batteries in series and you have a 48V system. That same voltage drop would only now be 0.75%, so you could get by with thinner (cheaper) wire. The problem with having a 48 volt system though is all the readily available appliances you can buy are for the RV market which is almost exclusively 12V. As Johnp states, most 48 volt systems are designed around it being converted to 110AC first before the electricity is used.


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## Studhauler (Jul 30, 2011)

So what is the typical inverter loss percentage when converting 48 vdc to 110 vac? If you have a 48 vdc system do you have to convert to 12 vdc or can you just tap off from one battery?


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