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Maxhead
22nd April 2014, 08:46 PM
Guys,

I have 2x200W panels which I'm going to charge a 12v battery bank via a MPPT regulator which will be near the bank of batteries. My problem is the most efficient position for the panels is around 30-35 meters away.

Is this possible? What size cable would I need? Would I have too much voltage drop to make it worth while?

Any input would be helpful


Cheers

mudski
22nd April 2014, 08:57 PM
Find out what they use for a house and use the same maybe? I had a quick look at the panel at my house and by the eye it looks around the 8B&S size. Wasn't hard look though. I take it the panels will be portable and not perma mounted to the ground?
Voltage drop is your issue over that distance so the heavier the better I guess.

Maxhead
22nd April 2014, 09:01 PM
Find out what they use for a house and use the same maybe? I had a quick look at the panel at my house and by the eye it looks around the 8B&S size. Wasn't hard look though. I take it the panels will be portable and not perma mounted to the ground?
Voltage drop is your issue over that distance so the heavier the better I guess.

Cheers mate, I'm going to fix the panels permanently and only change the angle between summer and winter so I'll run the cable underground in a pipe or so

mudski
22nd April 2014, 09:35 PM
I'd go see your local electrical supplies like Middy's or L & H etc etc then. Are they 12V panels?

Maxhead
22nd April 2014, 09:39 PM
Yep 12v panels

Winnie
22nd April 2014, 09:44 PM
I'd go see your local electrical supplies like Middy's or L & H etc etc then. Are they 12V panels?

They won't help... Nothing shit's me more than when people come in and tell me their application and ask what cable they need. I am not an electrician and I do not know the answer. Even if I did I am not allowed to tell them. I know a few blokes though Kris if I see them I'll ask the question.

mudski
22nd April 2014, 10:08 PM
Depends on where you go I suppose.

the evil twin
22nd April 2014, 10:18 PM
Guys,

I have 2x200W panels which I'm going to charge a 12v battery bank via a MPPT regulator which will be near the bank of batteries. My problem is the most efficient position for the panels is around 30-35 meters away.

Is this possible? What size cable would I need? Would I have too much voltage drop to make it worth while?

Any input would be helpful


Cheers

Yowser dude... you are going to need some serious cable. 8 B&S is too small for a 12 volt system and will drop over 20%.

400 Watts (or nearly 1/2 a kilowatt) of 12 Volt nominal Solar Panel array is going to supply maybe 25 amps at peak Solar.
25 Amps even thru 6 B&S is going to drop 10% or more over that distance and that much 6 B&S will cost you over $400 incl terminations.

Depends what you are wanting to do whether it makes it worthwhile

Cuppa
22nd April 2014, 11:48 PM
I’m not sure what size cable you would need, but it would be seriously heavy & seriously expensive, costing more than the rest of the system combined by quite a margin, so unlikely to be an economic proposition. Cheaper to connect the panels in series to give 24v & use an mppt regulator capable of taking 24v input to charge the batteries at 12v. This will allow the use of lighter cable but even then the cable is likely to cost a lot, although if you can pick up some secondhand welding cable you may be able to keep the costs within ‘manageable’ limits.

This link to a cable sizing calculator should help. http://www.solar-wind.co.uk/cable-sizing-DC-cables.html Base your calculations on 25 amps as ET suggests & have a play around with the other parameters.

Far better if you can find a way of siting the panels much closer to the batteries.

Cuppa

Maxhead
23rd April 2014, 04:50 AM
Hmm, I thought this might not be an easy or cheap solution.

I want to charge 2x120ah DC batteries which I currently have in parallel giving me 240ah. As my needs increase I could add another 120 maybe.

As all my lighting and appliances are 12v so I wanted to leave the system at 12v.

My regulator is capable of 12/24v so I could in fact turn it into a 24v system but I can still see losses here

My best option i think is to put the panels closer and have limited sunlight, I think this would still be plenty to charge 240ah with 400w.

This is for my shack out bush so it will only get used on weekends and holidays so no big or extended power draws will be required and a lot of time in between for charging.
Unfortunately, there are a couple of gums on the northern side of it making it hard but I still think I could get a decent ammount of sun.

The only other solution is a wind turbine but that's more cost when I already have the panels and batterues

Chimo
23rd April 2014, 06:36 AM
Or IMHO cut the trees down before they fall on the shack or the panels and have a shortened cable run.

threedogs
23rd April 2014, 06:47 AM
Is it poss. to build a small tower to sit them on, with a pivot system for summer and winter angles

Maxhead
23rd April 2014, 06:57 AM
Or IMHO cut the trees down before they fall on the shack or the panels and have a shorted cable run.


Yeah, not really keen on getting rid of shads trees. There are a couple of suss limbs I will cut off but not whole trees.

Maxhead
23rd April 2014, 06:58 AM
Is it poss. to build a small tower to sit them on, with a pivot system for summer and winter angles


Yes it's possible but the tower would have to be prettttty high to get full sun

Winnie
23rd April 2014, 07:11 AM
Build a little shed to store the batteries in closer to where you want the panels and the cable you would have to run back to the shack would be much smaller then.
What are you going to be running in the shack off the batteries other than lights?

threedogs
23rd April 2014, 07:21 AM
800 watt wind generator. just a suggestion

http://www.ebay.com.au/itm/6-Blades-Wind-turbine-generator-12V-800W-/181298744820?pt=AU_Solar&hash=item2a363f4df4

Maxhead
23rd April 2014, 07:28 AM
Build a little shed to store the batteries in closer to where you want the panels and the cable you would have to run back to the shack would be much smaller then.
What are you going to be running in the shack off the batteries other than lights?

Hmm, yeah I didn't think of that. There will only be LED lights inside and outside for a couple of hours a night. It will be used to charge the sat phone, run kids 12v tv/dvd on rainy days, possibly a 12v fridge as freezer on extended stays in summer.

Currently my estimation is average 15amps a day to 50amps max

Winnie
23rd April 2014, 08:02 AM
So max current draw would only be like 10-15A?
Cuppas website link says 50mm cable will work which is about $5-6 per metre.
Maybe 12v over that distance is not a good idea haha

Winnie
23rd April 2014, 09:05 AM
I just spoke to my solar man and he said what you are trying to do is ridiculous... haha. He said put the batteries as close to the panels as possible and even then the cable you will have to run to the shack will be huge. He said to find a way to put the panels closer to the shack.
I'll ask another bloke who is more likely to help out with dodgey shit haha

Bob
23rd April 2014, 09:15 AM
I would build a Rubber Wheeled Trolley to hold the Batteries and also the Fridge and set it up close to the Panels during sunlight.
Then wheel it back to the Shack for Night Lighting
You would probably need enclose the Batteries and Fridge on the Trolley

threedogs
23rd April 2014, 10:13 AM
Not as silly as it sounds and its only 30-35mtrs.
Just make an easy plug n play set up, save on a shite load of cable laying on the ground.

Winnie
23rd April 2014, 10:16 AM
I would build a Rubber Wheeled Trolley to hold the Batteries and also the Fridge and set it up close to the Panels during sunlight.
Then wheel it back to the Shack for Night Lighting
You would probably need enclose the Batteries and Fridge on the Trolley

Yeah there's one big problem there though, Kris passes out before dark so it will never get wheeled back in!

lucus30
23rd April 2014, 10:18 AM
If it was me I'd be spending the money and putting in a permanent set up. If it means spending $500 on cables then so be it. Mucking round with moveable trollies/panels would be a pita. Might be worth even setting up an adruino sun tracker

Bazhemps
23rd April 2014, 10:30 AM
My 2 cents, when I installed 200W panel to our van I went on line and purchased one cable cut it in half and used it for connecting the panel pos - neg to the reg. Can't remember what was the longest cable you could get!

the evil twin
23rd April 2014, 10:40 AM
Mate, it is all about balance. There is no point in having a wacking great Solar Array with a small battery bank or vice versa

I totally agree with Lucas tho and would make it "permanent" seeing as it is for the Cabin.

I assume from an earlier post you anticipate an average useage of 15 Amp hours and a max daily useage of 50 Amp Hours.
I would also assume you will only hit 50 A/H on "rainy days" IE lights, DVD player and fridge all on together.
On rainy days you won't have any Solar to offset the battery drain anyway so a big panel capacity/heavy cable won't help.
When you aren't there (Winter or Summer) a big panel capacity won't help as the battery bank will be float charging.
In summer you will have good solar days so a big panel capacity is not required to run/replenish 50 Amp Hours per day which you probably won't hit as no DVD and minimal lighting req'd.
That size battery bank will easily handle 3 days or so then happily replenish while you are away therefore you only need to consider longer stays during poor Solar days

That leaves Winter/Rainy days so IMHO you may need to look at a small wind generator or take a dinky genset for maybe 2 hours for when you are at the Cabin long term.

I do advocate "future proof" the setup IE if you bury the conduit but make it large enough for another cable and leave a draw wire in there

threedogs
23rd April 2014, 10:43 AM
You might be able to source an old southern cross pump tower and fit your panels to that.
I'd be spending to have the system permanent, I think but don't know your future plans eh.

Sir Roofy
23rd April 2014, 11:47 AM
winnie is right so forget the solar and get a pure sin generator
for kris,s needs ,will charge batterys during the day or night and dose,nt
need to be moved or follow the sun so when he sleeps in front of the fire
alls good lol

do lots of research kris theres that many different set ups the mind
boggles but you,l know wich one when you see it just like the block
you've got

lucus30
23rd April 2014, 12:55 PM
Also the higher your voltage the lower your losses are so I'd be going as high as possible. 24VDC is easy enough to get appliances for but have you thought about running an AC set up? You could use step-up and step-down transformers then your cable run could be as long as you'd like pretty much.

Maxhead
23rd April 2014, 04:02 PM
Thanks for everyones input, this forum is a great resource !!!

I have a few options to chew over for now.... This setup cost me peanuts so that's why I have it. I also have a 3.5kva genny so I can recharge batteries if needed.

Once I put my BIG MAN SHED/living quarters out there I will set up a proper 24v or 48v system and run 240ac but I still want a decent setup for the shack for now and for guests later on.

the evil twin
23rd April 2014, 06:47 PM
Thanks for everyones input, this forum is a great resource !!!

I have a few options to chew over for now.... This setup cost me peanuts so that's why I have it. I also have a 3.5kva genny so I can recharge batteries if needed.

Once I put my BIG MAN SHED/living quarters out there I will set up a proper 24v or 48v system and run 240ac but I still want a decent setup for the shack for now and for guests later on.

Thats the go... with a genny as "emergency" I'd bring the 12 volt panels as close in as possible and take whatever you can get.
Even at 50% they will handle what you have mentioned so far

When it is time for Big Mans Shed remember the higher the voltage the skinnier the wire so I'd def go domestic panels with a small off the grid inverter and battery bank not 12 or 24 Volt.

lucus30
23rd April 2014, 07:52 PM
Thats the go... with a genny as "emergency" I'd bring the 12 volt panels as close in as possible and take whatever you can get.
Even at 50% they will handle what you have mentioned so far

When it is time for Big Mans Shed remember the higher the voltage the skinnier the wire so I'd def go domestic panels with a small off the grid inverter and battery bank not 12 or 24 Volt.

I agree with evil twin this is what I'd be doing. Didn't realise it was a temporary set up