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Author Topic: Cable length, sizes and components  (Read 9921 times)
Stefan (S.T.E.F.)
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« on: January 20, 2009, 04:08:18 PM »

So now I've got my head around the forklift battery idea I am stuck with something else.
Cable sizes and components.
I don't have a problem working out 12V systems, but 48V/240V in a real life off grid system seems a bit scary.

My wind turbine (Miniwind 2200 48V) will be placed around 100m from the house. Some month ago I decided to put a shed close by for the battery bank, charge controller and inverter but I haven't put it up yet. I thought that it would be much easier and cheaper to run 240V over the length of 100m than 48V. That also means I have to run to the shed in any kind of weather to monitor the battery bank.

I am looking for some help with choosing inverter etc. and cables. What are peoples experience in real life off grid situations ?
I don't want to be having to buy several inverters or battery banks (destroyed by unsuitable chargers etc) because I have to rely on sales people.

Also any ideas how to monitor the battery bank from the house ?

Any help greatly appreciated.

Stefan 
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Justme
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« Reply #1 on: January 20, 2009, 04:20:31 PM »

Monitor the bank with a smartgauge, you can run thin wires for it & it will also auto start a genny if the genny has the right set up.

use Victron inverter chargers, you can stack then if needed for higher power of even 3 phase.

Use thick cables speced for volt drop not amp carry capacity.

Justme
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30 x 58mm panel 259L TS
1200watts solar 120vdc
FX80 Solar controller
2 x Victron Multiplus II 48/5000/70
Cerbo GX & GX 50 touch
BMV 700
6kva genny
48v 1000ah
Grid Possibly coming soon
stephend
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« Reply #2 on: January 20, 2009, 04:28:30 PM »

I don't have any real world experience with it, but I do like the look of the SMA sunny island AC connected approach.  Their web site has all the details, but in a nutshell, if you base your system on the sunny island inverters, you then run all your other power supplies and consumers on the AC side.  The only DC connected bit is the battery bank.  Since it's all 240V AC voltage drop is less and you have more freedom in placing your kit where you like.  Since all the producers are parallel, it means that the inverter isn't a bottleneck, i.e. if your inverter produces 3000W, your wind turbine 2000W and your solar panels 1000W, and it's a windy and sunny day, then potentially have 6000W available on the AC side.

Now for the bad bit: the system works only with other SMA products, so you'll have to buy a windy boy for your wind turbine and a sunny boy for any solar panels - these are much much more expensive than simply using DC charge controllers.  It depends on how much you value the flexibility and expandability of the setup.  More details on their website.
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Stefan (S.T.E.F.)
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« Reply #3 on: January 20, 2009, 04:39:21 PM »

I already had a look at the Victron web page and it all made no sense to me. But then I am an absolute beginner....
Which one would I need, I am looking at 4000-5000W to be on the safe side, as I don't fancy running through a gale force wind to reset the system after the wife has switched on the hoover without turning the TV off ;-)
The smart gauge battery monitor looks good. I will plan that into the system.

Stefan
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billi
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« Reply #4 on: January 20, 2009, 05:18:12 PM »

Stefan

Are you sure the  mini wind  will produce 48 Volt DC direct at the turbine , or  is it not having a separate rectifier , that then produces 48 Volt out of their 3 phase generator ?
I would find that out first

I prefer having the battery and the Inverter close to the house ....

Cannot say much about SMA  Island (but pretty good i expect) , but would estimate about 3000 pounds more then other systems ....

The Victron ( like the new Quattro , or two Multi Plus in parallel )  are pretty easy to install

With a good MPPT PV charge controller  ( takes upto 140 V DC and changes towards your 48 Volt bank) you keep cables thin
And a dumploadcontroller http://www.navitron.org.uk/product.php?proID=82

at your battery for the windturbine 

Nearly there

Billi
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Justme
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« Reply #5 on: January 20, 2009, 05:31:11 PM »

For lay out I would

Have the bank & the inverter very close but in sepperate air spaces to keep the heaviest cables short.
Have the inverter/bank housing as close as possible to the low voltage power producers (IE 48v DC wind turbines with bank at or near the tower).
Have the higher voltage power producers where they will work best (IE solar on the roof running at 140v dc).
Run high voltage (240v ac) to the house from bank/inverter.

That will keep the cable costs down & the volt losses reduced so increasing the power available over power actualy produced.


Justme
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Navitron solar thermal system
30 x 58mm panel 259L TS
1200watts solar 120vdc
FX80 Solar controller
2 x Victron Multiplus II 48/5000/70
Cerbo GX & GX 50 touch
BMV 700
6kva genny
48v 1000ah
Grid Possibly coming soon
guydewdney
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« Reply #6 on: January 20, 2009, 10:47:43 PM »

I thought the miniwind came in 48 and 230v versions. I have high voltage versions. Which might well be for sale very soon....

Can I advise to replace the bearings asap?
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Stefan (S.T.E.F.)
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« Reply #7 on: January 21, 2009, 11:55:39 AM »

Totally confused now. Yes, the miniwind comes in 300V as well, what would I do with that? Run 300V along 100m then into a 48V battery banK ?
See, thats where I need somebody who understands all this to design the system, but the two local electricians I have found told me they can't do it.
 faint
I need to understand it all myself and just get an electrician from further away to come out once and certify it all.

 surrender

Help !

I can supply a site plan if that helps.....

Stefan
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Stefan (S.T.E.F.)
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« Reply #8 on: January 21, 2009, 12:02:35 PM »

Monitor the bank with a smartgauge, you can run thin wires for it & it will also auto start a genny if the genny has the right set up.

use Victron inverter chargers, you can stack then if needed for higher power of even 3 phase.

Use thick cables speced for volt drop not amp carry capacity.

Justme

Smartgauge web page: "...suitable for 12V and 24V..."
Couldn't find one for 48V on there.

Victron: they charge the battery bank and change the voltage? That seems cool.

Thick cables: got that, I always work on volt drop, not amp capacity.

Stefan
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Justme
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« Reply #9 on: January 21, 2009, 12:30:11 PM »

Bog yeh forgot they dont do 48v.
Not sure what you mean about "change the voltage" on the victron. They do change 48v dc to 240c ac and back again.
For solar the MPPT controllers will accept a wide range of dc V to charge a bank of a different voltage.

Justme
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Navitron solar thermal system
30 x 58mm panel 259L TS
1200watts solar 120vdc
FX80 Solar controller
2 x Victron Multiplus II 48/5000/70
Cerbo GX & GX 50 touch
BMV 700
6kva genny
48v 1000ah
Grid Possibly coming soon
billi
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« Reply #10 on: January 21, 2009, 02:45:21 PM »

Quote
Totally confused now. Yes, the miniwind comes in 300V as well, what would I do with that? Run 300V along 100m then into a 48V battery banK ?

Why not just ring the Miniwind crowd and ask what size cable for a 48 Volt unit at 100 meter ?

My turbine is(was  sh*tfan)  24 volt DC  , but  the cable from the turbine generator ( as well 100 meter ) is 3 wire wild AC  with i think upto 300 Volt and then it was changed to DC 24 Volt in my workshop ( where all the rest of the gear is )

The Victrons have an AC 230 Volt connection ( beside the Connection to the battery) .
That means you can connect the Grid or an AC Generator to them
The power of the AC source is then switched through into your home and what you donot consume there  is changed to 48 Volt DC to charge the battery ( in parallel) and if you need more power then the generator supplies the rest then comes from the battery


 and when your generator is not running  all your power comes from the 48 Volt DC Batterie inverted  to 230 Volt AC by the victron

In my opinion this is a good feature , if you have a stable and clean Generator (i donot think you could connect a AC 230 Volt windturbine  to that)

I personally  had trouble with my AC generators = i use mainly  a DC generator(diesel) now to charge  the battery

Billi
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Justme
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« Reply #11 on: January 21, 2009, 04:00:18 PM »

Quote
Why not just ring the Miniwind crowd and ask what size cable for a 48 Volt unit at 100 meter ?


Every time I have done that with other suppliers they hugely under spec the cable using amp capacity & not volt drop calcs. I suspect they do this so when you get quotes for the cable its cheaper so does not put you off buying their kit. But they dont tell you that that cable will rob you of costly to produce power. Using bigger cable could allow you to down size the actual power producer as you are loosing less.

Justme
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Navitron solar thermal system
30 x 58mm panel 259L TS
1200watts solar 120vdc
FX80 Solar controller
2 x Victron Multiplus II 48/5000/70
Cerbo GX & GX 50 touch
BMV 700
6kva genny
48v 1000ah
Grid Possibly coming soon
Stefan (S.T.E.F.)
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« Reply #12 on: January 21, 2009, 04:16:19 PM »

From the Miniwind webpage:

"High-Power Cable
For use with our turbines and PMG's, this cable is very flexible, High-Power with a 10sq mm conductor area (8 AWG), available in Red or Black.  Ideal for connecting the DC power output from our turbines, down your tower to your batteries, charge controller, heating element or inverter.  Also good for making your battery bus bar connections.  The cable is sold per meter, and has the following specifications... # Volt drop of only 2.2mV/A/m"

That is the only cable they sell costing 3.50 per meter.
If I worked that out correctly I would have a voltage drop of 26V over the 200m cable run costing me 700.  Shocked

Stefan

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Justme
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« Reply #13 on: January 21, 2009, 06:29:14 PM »


If I worked that out correctly I would have a voltage drop of 26V over the 200m cable run costing me 700.  Shocked

Stefan



Like I said vastly under speced. I think for mains 3% is considered as ok. On my dc I have aimed for much much less.

Also quoting 10mm2 as good for bank bus bars is mad. Mine is 120mm2 & only 3m (1.5 red & 1.5 black).

Justme
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Navitron solar thermal system
30 x 58mm panel 259L TS
1200watts solar 120vdc
FX80 Solar controller
2 x Victron Multiplus II 48/5000/70
Cerbo GX & GX 50 touch
BMV 700
6kva genny
48v 1000ah
Grid Possibly coming soon
Stefan (S.T.E.F.)
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« Reply #14 on: January 21, 2009, 06:32:23 PM »

Stefan

Are you sure the  mini wind  will produce 48 Volt DC direct at the turbine , or  is it not having a separate rectifier , that then produces 48 Volt out of their 3 phase generator ?
I would find that out first

I prefer having the battery and the Inverter close to the house ....

Cannot say much about SMA  Island (but pretty good i expect) , but would estimate about 3000 pounds more then other systems ....

The Victron ( like the new Quattro , or two Multi Plus in parallel )  are pretty easy to install

With a good MPPT PV charge controller  ( takes upto 140 V DC and changes towards your 48 Volt bank) you keep cables thin
And a dumploadcontroller http://www.navitron.org.uk/product.php?proID=82

at your battery for the windturbine 

Nearly there

Billi

I emailed energistar about the rectifier. See what they say.
I would certainly prefer to have the battery bank etc in a shed at the back of the house.
SMA seems too expensive to me, won't be able to afford the wind turbine....
The Victron seems good for what I understand of it.
Dumpcontrollers have already been picked. 2x Tristar TS-60, just not sure what to dump to.
Thin air would be a waste. Don't need heating in the house or hot water, so a water store in the
poly tunnel I thought would be good, maybe I can grow bananas then...
 whistlie

Not really though about the PV yet, it seems to make more sense to invest into a lister first as
PV output won't be much in the Highlands. If a 110W panel would cost 100 I'd buy the 12 that
I had planned but at 400 it's a bit of an investment with not too much outcome. Would make
more sense in Spain....

Stefan
« Last Edit: January 21, 2009, 06:48:23 PM by Stefan (S.T.E.F.) » Logged

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