# 12V vs 24 V



## steff bugielski (Nov 10, 2003)

Can you please tell me, in very simple terms how the two systems differ. Of course beside the obvious that one is 12 v and the other 24. Do you gain anything? loose anything?


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## bbbuddy (Jul 29, 2002)

steff bugielski said:


> Can you please tell me, in very simple terms how the two systems differ. Of course beside the obvious that one is 12 v and the other 24. Do you gain anything? loose anything?


You save $ setting up higher voltage systems because the wire required to carry the current can be smaller without losing watts or overheating.

You also can have larger battery banks without paralleling a bunch of batteries, which results in poor recharging performance - the fewer parallel connections the better.

Usually to decide which voltage your system should be is 12v up to about 1000 watt loads, 24 volt up to about 2000 watt loads, 48v for everything else. But you must take into account that historically EVERYONE'S loads tend to grow, therefor what you think you need now PROBABLY will not be what you need later  so it's better(cheaper) to start out with a system that can handle larger loads.


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## ET1 SS (Oct 22, 2005)

Each decade the technology gets better. I see other homes in my area that are off-grid, some were done in the 70s, the 80s, and so on. It is interesting to see which level of technology existed when each home was setup.

There are homes that are wired entirely using 12VDC.

I was in a home Friday where he had 'ganged' two 120VAC invertors together to 'make' 240VAC for his well. Today they have invertors that internally make 240VAC. You do not need to gang two together.

Also now there are MPPT chargers, which is a huge advancement. But only in 24VDC and 48VDC systems, not 12VDC systems.

As technology gets better, you can do more things. It seems the better features are on higher voltage systems.


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## steff bugielski (Nov 10, 2003)

We have currently a 12 V system. We run just about everything. Our goal is to run everything. Our choice is get more panels or turn it into 24 V. 
We ordered 2 12 V - 120 Watt panels from some one on ebay. , when they arrived they were 24 V and 175 watts. They have refunded my $ but seem reluctant to issue a pickup. They have asked if we want them we can make an offer. So now I am thinking do I switch to 24 V. I have a diagram on how to switch from 24 Volt panel to a 12 Volt panel using a jumper in the junction box. What do I loose by doing this?

Also if you have two 12 v panels, one is 100 Watt and the other is 75 watt. Can you hook them in a series to get 24V ? How many Amps would you get?


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## ET1 SS (Oct 22, 2005)

steff bugielski said:


> We have currently a 12 V system. We run just about everything. Our goal is to run everything. Our choice is get more panels or turn it into 24 V.
> We ordered 2 12 V - 120 Watt panels from some one on ebay. , when they arrived they were 24 V and 175 watts. They have refunded my $ but seem reluctant to issue a pickup. They have asked if we want them we can make an offer. So now I am thinking do I switch to 24 V. I have a diagram on how to switch from 24 Volt panel to a 12 Volt panel using a jumper in the junction box. What do I loose by doing this?
> 
> Also if you have two 12 v panels, one is 100 Watt and the other is 75 watt. Can you hook them in a series to get 24V ? How many Amps would you get?


Two 24VDC-120W-5amp panels wired in parallel will give you 24VDC with 10amps.

In series they will give you 48VDC with 5amps.


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## solidwoods (Dec 23, 2005)

I was in a home Friday where he had 'ganged' two 120VAC invertors together to 'make' 240VAC for his well. Today they have invertors that internally make 240VAC. You do not need to gang two together.

WOW and the phase is sycronized?
jim


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## ET1 SS (Oct 22, 2005)

solidwoods said:


> I was in a home Friday where he had 'ganged' two 120VAC invertors together to 'make' 240VAC for his well. Today they have invertors that internally make 240VAC. You do not need to gang two together.
> 
> WOW and the phase is sycronized?
> jim


Yes invertors commonly have a terminal that you can connect to another invertor, so their clocks count together. This makes their output wave-forms to be synchronized.

With grounds tied together, and returns tied together. One 120VAC invertor can feed the 'A' line or phase of a 240VAC main-panel, the other 120VAC invertor can feed the 'B' line or phase. Together they can give you 240VAC.

In what you end up paying for a 12VDC system, to feed two 120VAC invertors and the wiring; it is cheaper to have a 24VDC system and feed one invertor with both 120VAC / 240VAC outputs.


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## wy_white_wolf (Oct 14, 2004)

steff bugielski said:


> ....Also if you have two 12 v panels, one is 100 Watt and the other is 75 watt. Can you hook them in a series to get 24V ? How many Amps would you get?


When wiring panels in series you add voltage but amperage (IMP) is limited to the lowest rating.

When wiring panels in parrallel you add the amperage but voltage (VMP) is limited to the lowest rating.

WWW


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## Alaska (Jun 16, 2012)

Im no elec guru but from what I have gathered living off the grid the last 4 years the higher the voltage the better.
we went 24v because the wind genny we chose is 24 v.
And I will echo what bbbuddy said expect your usage to grow. The more you make the more you use and yada yada yada it just keeps going from there.
Time for me to shop for more panels and another inverter.


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## Jim-mi (May 15, 2002)

For expansion you need the higher voltage .
"Monster" 12v systems can get pretty ugly....

Many many years ago I went with 24v . . .....because of a wind turbine i put up.
My inverter is 120---240 . . . .it has been pumping water (240vac) for 12 years.

If I were starting over today I would go with a 48v system..

24 to 12v converters are easy to come by so as to run what ever 12v stuff you have now.

The Better and Best quality inverters (Not the truck stop junk) are readily available in 24---48v.....
These inverters will far out last that truck stop junk


It would be a very good move on your part to upgrade your system to at least 24v....now
..


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## 12vman (Feb 17, 2004)

My system is 12 v.d.c. and has been since '89. My 120 v.a.c. useage is nill to nothing. The largest inverter I use is 400 watts and that's for a hot glue gun or to charge my battery powered tools..

My main power buss is a run of 2ga. wire ran the length of my building. I have one 30 amp fuse to protect the buss at the battery and fuses at the taps to my outlets or to whatever I have connected to it. I have never blown that 30 amp fuse..

12 volts is a simple voltage to work with and the electronics industry is focused around this voltage. It's easy to work with being that many electronic items can operate on voltages lower than 12 volts..

It's a matter of ac. or d.c. If one wants a d.c. system, it makes sense to be 12 volts. If one wants an a.c. system, then it makes sense to go with a higher voltage. Trying to manage a d.c. system with any voltage other than 12 volts can be difficult and expensive, IMO..


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## Jim-mi (May 15, 2002)

All good points 12vman.
And kudos to you for keeping your lifestyle simpler and being happy with a 'smaller' system. 

When the feces hits the fan you will be far and away ahead of those who are crying because "My dishwasher wont work"

Projecting down the road what you think you will need electric wise is not a easy task.
If your life style demands that you have a dishwasher than go with 48v
If you can keep your life style bare bones simple than go with 12v

With these troubled times we all face right now, there is a very huge argument toward greatly simplifying ones life style.


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## 12vman (Feb 17, 2004)

It ain't all that bad, jim-mi.. I gots me a 74" projection TV/DVD projection system with hillbilly surround sound.. 

I don't "invert" much but I do "convert" now and then..


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## cmcon=7 (Mar 7, 2010)

as far as a 100w and a 75w panels in series you can do it but the voltage on the 100w panel may read 18v and the 75w reads 10 volts but the current will be the same, I would not plan to do this but it;s not as bad as some might make out.
the lower the voltage the higher the current and all that.


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## CptJera (Sep 23, 2012)

Great input and info on this thread so far. That's a simple opinion from a newby. Here's a new wrinkle for you. I've just obtained a (pardon the upcoming string of acronyms!) APC rack-mount UPS that was being discarded. It's a Dell Smart-UPS 3000VA USB RM 2U 120V (model dla3000rm2u) with the RBC43 48 volt battery pack.
Amazingly enough, this unit has been sitting disconnected under a workbench for over 6 months and is still cranking out *52 volts DC* and when switched on fired up a clean 124 volts AC with no dropping for over 30 minutes right off the bat! Granted, there was no load on it at the time, but I really did expect to see the voltages fade after that long. And it was destined for the trash! I can imagine a huge number of uses for this treasure!!
Long and short of the point of my post: I intend to build my solar/genset systems to provide 48v DC invertable to 120v and 240v AC (Pure Sine wave). I'm leaning 48v supply for all the reasons stated above in the thread. Are there any "gotchas" I need to be looking for in such a set up? Thanks, everyone!


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