Higher voltage panels for off grid shed

madcowusa

Classic noob mistake. I'm really excited about solar and was planning on buying a Harbor Freight kit to learn all about off grid solar. In the mean time I came across some rather powerful and higher voltage panels for sale and impulse bought six of them figuring I could start with one panel and add others as needed. They're Sunforce 327W panels and the label indicates Voc = 64.9V and Isc = 6.48 amps and this voltage is substantially higher than most other panels. I suspect they're intended for grid tie operation where lengthy cables get expensive. Anyway, should I resell these or is there a charge controller that would be affordable to use with these units? I'd like to install 2 panels at first, eventually working my way up to using all six. Plan is to put these on a shed far from the house and charge up 4 Trojan T-105 batteries (adding more later), run occasional power tools through an inverter, power some LED lights, DC rain barrel pump, small energy star freezer, if possible etc.

Any advice on a charge controller, array setup or safety appreciated.

westbranch

Re: Higher voltage panels for off grid shed

welcome... well you sort of made the classic mistake of ready, fire, aim....


So you now have ~ 1960Watts of GT panels. They will supply in the vicinity of 1,430 watts in reality, which is common for all PV panels for a variety of reasons we can get into later.

Before you go any further you need to sit down and decide just what you want to run. A well designed system starts with defining loads, then moves to deciding on batteries that can supply those loads along with an adequate inverter, and then deciding on how many watts of panels you need to recharge the batteries.

Step 1 define your loads, this is best done with a Kill-a-Watt meter. for example http://www.amazon.ca/P3-International-P4400-Kill-Monitor/dp/B00009MDBU

waynefromnscanada

Re: Higher voltage panels for off grid shed

Do not jump the gun and sell those panels! There are many excellent MPPT charge controllers that can take full advantage of those higher voltage panels by down converting the voltage (sort of like a transformer) while upping the amperage, thus taking full advantage of the wattage supplied by those powerful panels.
Depending on what battery voltage you intend to go with, which will depend on your present and future loads, you may need a couple or 3 of those MPPT controllers to handle the amperage they will deliver to your batteries.
Don't sell the panels, take a deep breath, do some studying, ask questions etc, then decide what to do.
Honestly? I'd be as happy as a pig is that proverbial messy smelly stuff if I had those Panels. All the more so if I got them for a good price!!

SolInvictus

Re: Higher voltage panels for off grid shed

madcowusa wrote: »

Plan is to put these on a shed far from the house....

What is the distance between where the electrical cable would attach to the shed and house?

niel

Re: Higher voltage panels for off grid shed

as to charge controllers unless you want to be taken in by chinese junk then you will find only 1 cc can really handle those pvs well and that's the midnite classic. your voc is high and during cold temps the voc can rise higher than the max for other controllers and damage them unless you intend to parallel all pvs. pita as it involves more wires.

do verify the pvs are working by a isc test with appropriate meter aimed at the sun around solar noon. this involves high currents being shorted through the meter and should be done quickly and safely. use either a high current dc switch or provide a means to shade or cover the pv in being tested.

i'm not sure what you may power with this system as where you are, the time of year it is, how aimed, etc come into play as well as how long and at what level your loads will be drawn for. you did put the cart before the horse, but it doesn't mean it is no good. with 6 of those pvs at 327w that 1962w as said may not always present itself at that level, but it is possible on occasion. fro a design standpoint we'll use the 1962w as the output. looking at a 24v battery setup as would 4 t105 batteries could make the output possibly seen through the cc would be 1962w/24v=81.75a. this is beyond all ccs except the classic and to use at a 12v battery level would mean more than one controller so i don't recommend a 12v battery arrangement for that and other reasons. now at 48v for the battery bank this is half the current or 40.75a and is in the realm of other ccs abilities, but the charging volts being inputted will necessitate at least banks of 2 in series for the pvs. if the voc goes too high for another cc make it will damage the cc. the classic 150 has hypervoc which is a buffer for the input voltage about equal to that of the battery voltage affording protection from damage, but will not operate at that higher level above 150v so the option is there for the classic 200. output current capabilities go slightly lower with the higher battery volts, but not by allot and your array would be well within the parameters of the classic.

you can play with the midnite string calculator either on the midnite solar page for naws or from the midnite site.

do note that the pvs you have can output much higher currents than many batteries can take in and many controllers have the ability to cut back on its output current with a setting. until you have a higher current capacity this cutback is recommended. trojan recommends a charge of about 10% of capacity, but you can go a bit higher like 13% or so. remember that is real time input current and it may take another 23% or so in pv power output to reap it as the stc ratings on pvs aren't typical real time numbers. system efficiency overall will also come into play reducing the actual watts realized by the system compared to the stc pv watts.

it is recommended that you come up with a final battery bank with all upgrades within a year or so of the initial battery purchase (go by battery manufacture dates) and them not being abused so that the newer batteries are not needlessly drawn down to a lesser level equaling the worst batteries in the bunch. due to the pv array you purchased and a rough idea of your loads i believe you should have a classic 150 or classic 200 along with a 48v battery bank consisting of 2 banks of 8 t105s and if you haven't bought the batteries yet upgrade to l16s for the proper voltage.

bill von novak

Re: Higher voltage panels for off grid shed

madcowusa wrote: »

Anyway, should I resell these or is there a charge controller that would be affordable to use with these units?

Sure. Apollo Solar T80HV MPPT, Blue Sky SB3048 (lower current), MidNite Classic 150 (for 6 parallel) or 200 (for 2s3p) Morningstar Tristar MPPT 60, Outback Flexmax and the Schneider/Xantrex XW MPPT series should work. You will see a (rated STC DC) 82 amps at your output but due to real world efficiencies and deratings 60 amps is probably plenty. In general you'll want to go as "series" as you can to reduce wiring costs. Using an XT MPPT 80-600, for example, you could put them all in series and run at a system voltage of ~350 volts.

(I assume you will be running a 24V system based on your batteries.)

I'd like to install 2 panels at first, eventually working my way up to using all six.

In that case 2s3p or 6s arrangement (with the high voltage MPPT controller) would be a good way to go.

Plan is to put these on a shed far from the house and charge up 4 Trojan T-105 batteries (adding more later), run occasional power tools through an inverter, power some LED lights, DC rain barrel pump, small energy star freezer, if possible etc.

I assume this project is just to experiment with solar and not to get power to the shed cheaply, right?

madcowusa

Re: Higher voltage panels for off grid shed

bill von novak wrote: »

Sure. Apollo Solar T80HV MPPT, Blue Sky SB3048 (lower current), MidNite Classic 150 (for 6 parallel) or 200 (for 2s3p) Morningstar Tristar MPPT 60, Outback Flexmax and the Schneider/Xantrex XW MPPT series...

I assume this project is just to experiment with solar and not to get power to the shed cheaply, right?

Thank you all for the input. I'm reading about these charge controllers mentioned, watching as many Youtube videos as I can and reading the 2012 Solar Electricity Handbook. Yes, this is an experiment/self education at becoming more self sufficient rather than need or monetary savings and probably mixed in with a bit of rebellion against the matrix by way of 'free' electricity. I have some acreage that I want to build a fully off grid home on next year and move this setup over there one I fully understand it. These gorgeous 327W mono-crystalline panels were on Craigslist for $200 each, brand new on original shipping pallet and not stolen, so not a ton of money spent (yet). Which brings me to the question of wires and fusing:

If I bought a ~$650 Midnite Solar Classic 200, configured the panels 2s3p and have a distance of only 15 feet from shed roof to the CC, battery, inverter location, what are the wiring considerations from the solar panels to the equipment? Is there a detailed diagram of a typical 2kW off grid system? I'm assuming I need a junction box to combine the cables with a breaker and disconnect. Can I just use the standard MC4 connectors to join two panels and then then some 15' ones with one end without a connector to run into the combiner box terminals? I want to be safe and have no problem spending the money on heavier cables if needed. Thanks again for all the guidance. I hope to pay that back in the future as I get more knowledgeable about solar.

Vic

Re: Higher voltage panels for off grid shed

The MidNite Solar String Sizing Tool is the best sizer that I've seen, and the easiest to use (just as is the MidNite Classic line of CCs):

http://www.solar-electric.com/misoclcoto.html

FWIW, My opinions, Good Luck, Vic

vtmaps

Re: Higher voltage panels for off grid shed

madcowusa wrote: »

If I bought a ~$650 Midnite Solar Classic 200, configured the panels 2s3p and have a distance of only 15 feet from shed roof to the CC, battery, inverter location,

You mentioned four T-105 batteries... so I assume you are building a 24 volt system.

My advice: buy a classic 150 and put your panels in parallel. With only 15 ft for the combiner-controller cable, you don't need such high voltage. The Classic 150 will be cooler and more efficient because it is down converting from 60 volts rather than 120. As a bonus, the Classic 150 can also handle more power than the classic 200.

--vtMaps

jcheil

Re: Higher voltage panels for off grid shed

madcowusa wrote: »

These gorgeous 327W mono-crystalline panels were on Craigslist for $200 each, brand new on original shipping pallet and not stolen, so not a ton of money spent (yet).

That is a REALLY cheap price, almost too good to be true. Perhaps the person selling them doesn't know the value of them and you can take advantage of that; but a (new) MONO panel at $0.61 per watt sounds like something is up with them.

madcowusa

Re: Higher voltage panels for off grid shed

jcheil wrote: »

That is a REALLY cheap price, almost too good to be true. Perhaps the person selling them doesn't know the value of them and you can take advantage of that; but a (new) MONO panel at $0.61 per watt sounds like something is up with them.

They're legit. Something to do with non payment by original buyer, a shipping company wanting payment and the manufacturer eventually writing them off due to return freight costs. The seller had zero interest in solar and just wanted them out of his way. I was too busy drooling over them to inquire more and distracted calculating how much food my family could forgo next month so I could grab a few more panels. Now I'm on a crash course of learning so I can put these to use.

Skippy

Re: Higher voltage panels for off grid shed

I picked my panels up at $0.77 a watt . . there are good deals out there if you can find em. . . but the buyer has to beware. . .

My next step is the wiring and batteries as well . . here is my thread. . .
http://forum.solar-electric.com/showthread.php?18603-Ready-!-Aim-!

I am looking at a morningstar 60 amp controller, with 500 amp hours or so of 24 V batteries, and a 2 kw inverter. - STILL researching . .