Author Topic: 12V -vs- 24V -vs- 48V  (Read 20763 times)

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Bischofk

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12V -vs- 24V -vs- 48V
« on: April 01, 2009, 03:28:57 PM »


Im sure this has been discussed but I cant seem to find anything in the FAQ or by searching so here goes. I am trying to decide what voltage unit I want to go with.  Ive seen in many places that higher voltage machines are preferred because of the lower currents involved, thus lower line loss of power.  Is this the only consideration?  If higher voltage is better, why is it so common place to build 12V systems?  


Thx guys!



Moved to the proper section.

« Last Edit: April 01, 2009, 03:28:57 PM by (unknown) »

Flux

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Re: 12V -vs- 24V -vs- 48V
« Reply #1 on: April 01, 2009, 09:49:18 AM »
Depends what you want to do. If it is a small set up for a cabin or something then 12v has the advantage that there are a lot of small items available that can run directly from the battery. These things are usually available for RV and boats.


If you want something bigger and you will use an inverter for quite a lot of things then to be perfectly honest 12v becomes a liability. If you are looking st something at 1kw or over then starting with 12v will cramp your style and cause endless frustration if you want to expand.


If this is serious power use for off grid living then virtually everything points to 48v . The snag is that it brings you up into the professional equipment range and cost is high. Even switches and breakers need to be considered carefully.


If you want a modest system using an inverter but you are not a real serious off grid user dependent on wind power then 24v is far better than 12v but you still can get cheap inverters and the problems of switches is far less. Common ac switches and breakers usually handle 24v.


I wouldn't consider anything over 500W for 12v. Up to about 3kW 24v can be quite effective and probably still reasonably cheap. If you are going with the big boys then 48v is the way to go but it becomes expensive, fine if you are totally dependent on it, but if it is part energy saving or part hobby or just a small set up then 24 may suit your needs.


If you get into serious power then even 48v is too low but at higher voltages you have many issues to cope with.


Flux

« Last Edit: April 01, 2009, 09:49:18 AM by Flux »

Bischofk

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Re: 12V -vs- 24V -vs- 48V
« Reply #2 on: April 01, 2009, 02:31:27 PM »
Outstanding, then I THINK you may have made up my mind to go with a 24V system.  I also did notice that 48V inverters were much harder to come by and were EXTREMELY expensive.  Well now Ive gotta find a nice 24V design and go with that :).


For the record, I want to build something that produces 500W+ in about 20mph of wind.  So nothing huge to start.  This is my first turbine.  

« Last Edit: April 01, 2009, 02:31:27 PM by Bischofk »

Airstream

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Re: 12V -vs- 24V -vs- 48V
« Reply #3 on: April 01, 2009, 02:46:31 PM »
Don't confuse price with value - one usually gets what they pay for...
« Last Edit: April 01, 2009, 02:46:31 PM by Airstream »

ghurd

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Re: 12V -vs- 24V -vs- 48V
« Reply #4 on: April 01, 2009, 04:12:13 PM »
Check what is available in your location.

The 24V decent reasonable priced stuff is often not where I am located.

G-
« Last Edit: April 01, 2009, 04:12:13 PM by ghurd »
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thirteen

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Re: 12V -vs- 24V -vs- 48V
« Reply #5 on: April 01, 2009, 06:27:38 PM »
There is alot of good information on this board. I would make a list of what you will need and check the power usage for everything thus haveing a total idea of your power demand. You will be able to build a good system. As a suggestion look into the future for things you might get. There are also tax breaks on new appliances, water heaters, and other items. It might help to check into these things for some money back. Best of luck. Just an idea.
« Last Edit: April 01, 2009, 06:27:38 PM by thirteen »
MntMnROY 13

Bischofk

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Re: 12V -vs- 24V -vs- 48V
« Reply #6 on: April 01, 2009, 07:27:02 PM »
Well unfortunately (or fortunately), I live in a 2 year old house with all high efficiency appliances.  Also all my major appliances (water heater, dryer, furnace) all run on natural gas.  So really the only major appliance that runs on electric is my AC.  I dont think my first project will even come close to running that monster, however, I am hoping to get my basement (TV, multimedia, computer, and perhaps lights) to run off of the batteries when power is available, and possibly have a switching system to turn back to grid power in the case that my batteries are low/dead.
« Last Edit: April 01, 2009, 07:27:02 PM by Bischofk »

imsmooth

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Re: 12V -vs- 24V -vs- 48V
« Reply #7 on: April 02, 2009, 06:39:09 AM »
I'm designing my stator for voltages between 50v and 350v for a grid-tie inverter
« Last Edit: April 02, 2009, 06:39:09 AM by imsmooth »

madkane

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Re: 12V -vs- 24V -vs- 48V
« Reply #8 on: April 02, 2009, 09:19:47 AM »
 i like this question as its one i wondered as well but  whats the draw back of going in for a 48 volt gen and bats  but just  have 2 24 volt inverters coming of the batteries
« Last Edit: April 02, 2009, 09:19:47 AM by madkane »

wpowokal

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Re: 12V -vs- 24V -vs- 48V
« Reply #9 on: April 02, 2009, 09:36:10 AM »
Simply it is unlikely the two inverters will draw equal current, even averaged over a day.


This will seriously unbalance the batteries, say there is 10 amps charging a 48V battery bank, the 10 amps flow through all batteries. Now if one was to draw 50 amps off the first 24volts of batteries and 10 amps off the second 24v half each half would be at a different state of discharge and this charging current would bring the second half to fully charged much quicker than the first half it follows that they would then be "overcharging" while the first half is still coming up to full charge.


allan down under

« Last Edit: April 02, 2009, 09:36:10 AM by wpowokal »
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wpowokal

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Re: 12V -vs- 24V -vs- 48V
« Reply #10 on: April 02, 2009, 09:46:18 AM »
In my experience the most common failure of inverters after operator error is the large electrolytic capacitors.


Probably the most significant single factor causing these to fail is temperature, caused by the  environment and current they handle. Therefore for large loads higher voltages have less current and hopefully longer inverter life.


Someone has already stated "you get what you pay for", if it's your only power supply there is no substitute for quality therefore nickle and dime stuff from the local hardware is unlikely to be successful long term.


allan down under

« Last Edit: April 02, 2009, 09:46:18 AM by wpowokal »
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madkane

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Re: 12V -vs- 24V -vs- 48V
« Reply #11 on: April 02, 2009, 10:03:56 AM »
so the drained batteries  wont try and suck the life out of the higher charged bat to equalise to a point

thanks for the answers
« Last Edit: April 02, 2009, 10:03:56 AM by madkane »

wpowokal

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Re: 12V -vs- 24V -vs- 48V
« Reply #12 on: April 02, 2009, 10:20:43 AM »
It just is not practical, there are grounding issues just to name one.
« Last Edit: April 02, 2009, 10:20:43 AM by wpowokal »
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zap

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Re: 12V -vs- 24V -vs- 48V
« Reply #13 on: April 02, 2009, 10:34:00 AM »
Here's a poll on system voltages from about a year ago with some good comments.

http://www.fieldlines.com/story/2008/4/22/03122/1591


I can't find the actual poll... maybe an admin will chime in if the actual poll still exists.

« Last Edit: April 02, 2009, 10:34:00 AM by zap »

TomW

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Re: 12V -vs- 24V -vs- 48V
« Reply #14 on: April 02, 2009, 02:19:25 PM »
Zap;


I found this:


http://www.fieldlines.com/poll/1208823889_wZykrztZ


Not sure if regular users can see it. It is almost exactly a year old.


Tom

« Last Edit: April 02, 2009, 02:19:25 PM by TomW »

zap

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Re: 12V -vs- 24V -vs- 48V
« Reply #15 on: April 02, 2009, 07:03:15 PM »
Thanks Tom, that's the one.


I tried a few different addresses to try and get to some kind of poll page tree and under search I did get some old poll pages to come up but never could get to the one you posted.

« Last Edit: April 02, 2009, 07:03:15 PM by zap »

zap

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Re: 12V -vs- 24V -vs- 48V
« Reply #16 on: April 02, 2009, 07:10:41 PM »
Tom is there a tree or page that lists all polls that an end user can get to?  Some do come up under a search but not consistently.


It would be interesting to see both the "system voltage" and "How Much Renewable Power are you Making" polls side by side... and maybe a few others.

« Last Edit: April 02, 2009, 07:10:41 PM by zap »

wooferhound

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Re: 12V -vs- 24V -vs- 48V
« Reply #17 on: April 02, 2009, 08:21:32 PM »
In the Poll box on the righthand side of the page

Select "Other Polls" . . .

« Last Edit: April 02, 2009, 08:21:32 PM by wooferhound »

richhagen

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Re: 12V -vs- 24V -vs- 48V
« Reply #18 on: April 03, 2009, 03:05:07 PM »
Usually the results are drastically shortened life for part of the batteries because of over charging or over drawing.  Thats if you sort out the grounding issues.  Rich
« Last Edit: April 03, 2009, 03:05:07 PM by richhagen »
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zap

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Re: 12V -vs- 24V -vs- 48V
« Reply #19 on: April 03, 2009, 10:28:54 PM »
Thanks woof, I thought I'd seen a link somewhere before.
« Last Edit: April 03, 2009, 10:28:54 PM by zap »