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  • New Build...

    So, just getting going on a new build. I think I'm a *little* undersized on panels, and oversized on inverter - but i'm trying to plan what I can for growth.. (and I know about battery banks and 'not adding new batteries).

    I'm looking at over 8K CDN to get electricity into my lot - and after the 8K, I'll get ... wait for it..

    A meter.

    Anything else is extra expense - and the minimum bill (because I"m in Ontario, and its not my principal residence) is about $120/mo ... just to run the meter to monitor itself. My best friend has a place 12km up the road, his bill in the winter, if he doesn't do a disconnection, is about that - so I'm not really guessing... so.. there's a lot of incentive for me to not go on-grid unless I have no choice. 10-11K in the first year buys a fair amount of system.

    So... here we go:

    6 x Canadian Solar CS6K-300MS 300W panels.
    1 x Magnum PT-100 Charge Controller
    2 x GB Industrial 804Ah 12V 6-cell batteries.
    1 x Magnum 4024-MS 4000W/120V inverter (stackable, but this unit only puts out 110V)
    1 x Magnum MMP250-60S
    1 x Midnite 3-string combiner box.

    2 strings, 3 panels each, room to add a 3rd string (and I can go up to 4 panels per string for expansion if I need.. the PT-100 has the overhead.

    I think that works out - for now - to 97 volts/19 amps for the Array, so.. up to 70-ish amps available for charge? Not sure I did the math right. I've seen on some of the posts a charge rate of C/8 , which is 100 amps; that's the max for the charge controller for a bank this size; i've also seen it posted that some batteries should be limited to C/20, and seen people say C10;

    I have about 8 sun hours in the summer; it does drop to 3 sun-hours in the winter but (for now) we are only using this 3-season.

    Do I need to add panels for charge purposes? Or should this hold me up - I should never get down as low as 75% charge on this setup; i have not yet purchased the batteries -- if I need to get a smaller bank, or if 2 extra panels is going to 'smooth this out' down the road, i'm fine with that.

    The intent is to build a residence over the next few years - up to 24 of these panels, a second charge controller, and another 4024 stacked (feeding my panel at 120/240, shared neutral. Yes, the inverters are designed for it, not letting out any smoke).

    I don't have yet, but am planning on adding an AGS / propane generator , and yes, in about 5 years when the additional panels come online, I will need a new battery bank, I think. I don't think , once we are onsite fulltime, my 800AH is going to cut it.

    In my house in the city - with an electric dryer, and central AC, we run about 14-16Kwh/day. I'm estimating 8-9 without those appliances, based on the rest of the stuff in my house - but that's longterm. Short term, we need a few lights, a small laptop computer, a stereo, and a well pump.

    (well pump is a whole different scenario where i will have questions, once I sort out what the code rules are for a water system)....

  • #2
    Hey Droo - Welcome to Solarpaneltalk (since I see it's only your 2nd post)

    I am actually using those same panels on a few of my off-grid cabins, and they run around 39VOC each (sticker says 39.7VOC) , so with three in series, you're looking at more like 120VDC during normal conditions, then don't forget to add some buffer for coldest temperatures (my 2 panels in series recorded a record high of 88VOC during a particularly cold February morning this year. i'd venture it was around -22C (my logger recorded battery temp as -18.5C at the time, and they're in an enclosure). So 3 in series would have been about 132VOC.

    I quick googled your controller so you look ok on that front (appears to be 200VOC rated). Just wanted to straighten up your math so you're not mistaken since that can really wreck some hardware fast.

    Your approximations for amperage from the array are correct, but only for that brief few minutes during the day when the sun is perfectly aligned with the panels, and assuming you've mounted them at the optimal angle/orientation. So I'd bank on getting a little less into your batteries. Also, I doubt you're going to get 8 "Sun Hours" a day, even in the summer. but perhaps I'm wrong. The Canadian government has a spreadsheet available with estimated solar insolation data for hundreds of cities/towns, as well as "sun hours" estimates for various panel mounting angles. You can google it pretty easy, it's on the NRCAN website. "Sun Hours" refers to how many hours worth of 100% rating you'll get from your panels (sorta - simplest explanation). So if you are expecting 4 sun hours, you'll get 4x 900W x 2 strings each day. Or approx 7.2KWh generated. Of that generated power, you'll get about 80% of it into your batteries (assuming the batteries are capable of accepting that much charge, and no other loads steal the power during the day) due to efficiencies of the charging circuits, and the batteries themselves.

    Your inverter will probably run around 80-90% efficient, but you'll lose a bit of energy to cabling and connections and such, so just assume 80% to be safe. So of the 7.2KWh we generated in our example, you get to use 4.7KWh of it as AC Electricity (7,2 x0.8 (charging) x0.8 (inverter) = ~4.7) You'll also lose up to 0.6KWh of energy per day from your inverter running. It'll be less, but you should be aware of the "parasitic" or "idle" losses. (Your 4024 unit is listed as 25Watts)

    I'm still relatively new to solar, and I used this format to estimate my system and it is currently outperforming my expectations, but over time the panels will deteriorate a little and you'll always have cloudy days so it's really a lot better to have lower expectations.

    Your batteries, in series, appear to be about 19KWh total storage (I'm assuming the 804Ah is determined from the 20hr discharge rate?) but you'll get a little more than that to start, and less towards the end of the batteries' lifespan.

    If you're estimating 8-9KWh/day usage, your system is grossly undersized IMO. I would take a hard look at what your expected loads will actually be (using Watt-Hours), add some buffer room because it will probably be higher than you think, and then figure out what you can cut/trim out.

    Make a list of every little thing you run, and how long it runs for. I'm talking cell phone chargers (they still suck power when they're plugged in and not actually connected to the phone), TV's, lights, fans, coffee makers (a big power suck), microwaves, laptops, etc. I'd suggest buying a cheap Kill-A-Watt meter and using it to check out various appliances/devices to get a rough idea what they consume. It just plugs into the wall and you plug your device into it, then it monitors KWh consumed. That was probably my best pre-solar purchase. Really helped me understand how much power everything consumes.

    If you're really just running a few lights and a laptop in the near future, then the system is probably fine - but you need to make sure you're 100% honest with yourself about what you need, or you'll end up running too much and causing yourself headaches, plus costing extra money in the long run. It's a good idea to get the quality products right out of the gate, like you appear to be aiming for, so that's great. but I figured I should probably be a bit critical now, before you buy, so you can make sure you're happy with the system.


    Forgot to address charging rates - you can contact GB and ask what they preferred charging profile is for the battery. They'll give you the rough amp rates they suggest, and you can figure out if you're good there. C/8-10 is probably a safe bet though if it's a Flooded Lead Acid style. So 80-100Amps is good. Add the extra panel to each string if you can, it'll help make sure you have the power available for a fast recharge in the event of a couple cloudy days.

    I should probably also mention that with your end-game goals of 8-9KWh/day system - you're going to get told you should look into a 48VDC system. your inverter is capable of 4000W, which is around 200Amps draw from your batteries. If you're planning to stack a second one on later, you're going to be trying to pull up to 400Amps from a battery bank. That cabling is going to need to be huge. and expensive. and huge. And your batteries may not like that sort of draw anyway. (Voltage from the batteries will drop significantly when pulling large currents thanks to the internal resistance of the battery)
    Last edited by Xplode; 04-23-2019, 12:51 AM.

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    • #3
      I had the lot monitored last summer where the panels are going 7.8 sun hours through 4 weeks June) July .

      I only have 3 feet from inverter to batteryN. Intending to use 4/0 cable. For the next several years, loads will be very, very small. The large load numbers are my current in-city home whch has a lot more stuff - and more people in the house. I don't expect to every get that high up north, but I will be monitoring that more closely when I get to serious upgrade time

      I'm not so concerned about undersized for now - that battery will hold up my loads for 5-6 years. ( Construction is a long term plan) .

      I got the 4024 for a song so I'm not opposed to a migration to 4048s in a few years - for now my concern is primarily around array size vs charging the battery.

      The voltage number I had was from plugging the vmp and isc into the magnum pt100 calculator, so I can't explain the difference there.. ...

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      • #4
        Vmp and Voc are two different numbers listed on the panel, so that's probably where you got that from. 32.5V vs 39.7V can make a big difference.

        Ok, well if you've done your homework on the sun hours thing then it's all good. What's your latitude at your install site? I'm up around 52degN and I won't get anything near that. Maybe 5.x sun hours.

        Comment


        • #5
          The calculator asked for both numbers.. I did put both in, that was what it shot back at me.

          I'm well South of you, 44.4

          Comment


          • #6
            Originally posted by Droo71 View Post
            I had the lot monitored last summer where the panels are going 7.8 sun hours through 4 weeks June) July .
            What do you mean by 7.8 sun hours?

            Do you mean hours of no shadow? or are you actually talking about Sun Hours which is quite a bit different.

            http://www.aurorasolarenergy.com/ave...ily-sun-hours/

            You seem to have a very small array for charging a 24V 804Ah battery bank. in off grid you are going to not just need the amps but the hours so many find that an east/west or south east / south west array works better to get the hours.
            You are also going to have loads during the charging hours cutting into your charging power...
            OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

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            • #7
              Peak insolation .15.83 hours max daylight end of June. April May June are very high sun months on the site. August is about 25% less energy available then June.

              Loads are mostly weekend only; it's inbound charge current for the batteries that concerns me . I'm solid on my usage for several years, but everywhere I look gives me different, and confusing info for how much current do I need, and how much is safe, and how do I calculate that info through the charge controller.

              Yes, I am concerned the array is a bit small. Or a lot small . Mounting is a premium, because I have no building, only ground mount, and mostly in granite. So I could consider smaller batteries, but if like to be certain on the math

              Comment


              • #8
                Originally posted by Droo71 View Post
                Peak insolation .15.83 hours max daylight end of June. April May June are very high sun months on the site. August is about 25% less energy available then June.

                Loads are mostly weekend only; it's inbound charge current for the batteries that concerns me . I'm solid on my usage for several years, but everywhere I look gives me different, and confusing info for how much current do I need, and how much is safe, and how do I calculate that info through the charge controller.

                Yes, I am concerned the array is a bit small. Or a lot small . Mounting is a premium, because I have no building, only ground mount, and mostly in granite. So I could consider smaller batteries, but if like to be certain on the math
                FWIW, on the insolation issue:

                The number of hours the sun is above the horizon and what is confusingly called "sun-hours" are 2 different things. The first term means some but not much quantitatively. The second is an anachronistic term for insolation : 1 "sun-hour" == 1 kWh/m^2 of insolation. Both terms assume unshaded solar exposure.

                The matter is further confused, especially for the uninitiated by whether or not the insolation being discussed is referenced to a horizontal surface, or to the plane of the panels.

                Usually, when used to discuss a site's solar potential, its' the Global Horizontal Insolation that's referenced ("GHI"). If so (and that's the usual and accepted convention for resource measurement orientation), that number needs to be translated/transposed to the insolation that's available in the plane of the array ("POA" insolation).

                Unless the panels are horizontal, the two numbers will be different. Shading aside, in panels are not horizontal, POA insolation will always be greater than GHI. That's usually the biggest reason you'll most always see arrays tilted to the horizontal and pointed south, especially in the Great White North, Ehh ?

                Invest 20 minutes or so and save yourself future time and confusion and look into something called PVWatts on the net. Read all the help screens for a short primer before you make any runs.

                Welcome to the neighborhood.

                Comment


                • #9
                  Originally posted by J.P.M. View Post

                  FWIW, on the insolation issue:

                  The number of hours the sun is above the horizon and what is confusingly called "sun-hours" are 2 different things. The first term means some but not much quantitatively. The second is an anachronistic term for insolation : 1 "sun-hour" == 1 kWh/m^2 of insolation. Both terms assume unshaded solar exposure.

                  Welcome to the neighborhood.
                  I've done that; no confusion here in insolation. We ran a monitor . Summer avg 7.8kwh/m2 , winter, a little under 3. Summer daylight peak, 15.83 hours . I'm not planning on any winter use for at least 5 years in any case.

                  I'm using the different numbers based on an Environment Canada spec and test.

                  Comment


                  • #10
                    Those are POA onsite numbers, though , not GHI.

                    Comment


                    • #11
                      Originally posted by Droo71 View Post

                      I've done that; no confusion here in insolation. We ran a monitor . Summer avg 7.8kwh/m2 , winter, a little under 3. Summer daylight peak, 15.83 hours . I'm not planning on any winter use for at least 5 years in any case.

                      I'm using the different numbers based on an Environment Canada spec and test.
                      This is NOMB, but you are confused. You might get 9.0 kWh/m^2 per day incident on a 2 axis tracker in June/July, but you'll never see 15.83 anywhere in the world on a surface of any orientation, much less in Frontenac ON.

                      I'm guessing a more realistic number for max. likely available insolation for a fixed orientation array optimized for summer production in Frontenac ON might be closer to 4.5 - 5.0 kWh/m^2 per day in summer.

                      PVWatts for Frontenac ON shows GHI of ~ 3.9 kWh/m^2/day and POA for a 30 deg. tilt at ~ 4.6 kWh/m^2 per day.

                      Based on living in upstate NY for ~ 45 - 50 years, I tend to believe those numbers. Not only am I quite familiar with the area also having spent a lot of time in southern ON, particularly in/around the Thousand Island area and environs both summer and winter, but I'm reasonably familiar with the solar resource and its worldwide distribution.

                      Can you please provide a conversion from the Environment Canada numbers to kWh/m^2 per day ?

                      Also, can you please describe your monitoring equipment ? You do know it takes a pyranometer to monitor irradiance and insolation, right ?

                      Like I wrote, NOMB but you're confused about the solar resource availability for your site and/or you're not using the same units of measurement. You sure you're not using Joules/m^3/day instead of kWh/m^2 per day ?

                      Comment


                      • #12
                        Seems to me regulations are going to require water, and you say your own well (pump). That in itself is
                        going to make it very difficult to be off grid. Do not forget, getting that motor started might take a peak
                        of 5 times running current. I suggest you design your project around this problem. At that point a grid
                        tie might start to look a lot more attractive.

                        I do not understand $120 a month for a meter, mine is only $15 USD. Bruce Roe

                        Comment


                        • #13
                          JPM , I'm not saying 15.83 'sun-hours'. that's the total peak 'daylight hours'. Not at all an insolation number. My site had a kit from EC on it the year before I bought it- the guy from EC provided me the summer/winter numbers of 7.8 and just under 3 , as my insolation numbers. I certainly don't have the skill to do that, but the Environment Canada guys surely did. At least, I would hope so. I think you're seeing the numbers and getting upset at the 'this is how long my daylight hours' last number and not reading where I am saying 'Sun-hours' or insolation numbers *7.8 peak in summer*, versus 'total daylight' - NOT insolation. And its a bit under 3 in the winter , which makes me glad that at this point, I"m not there in the winter.

                          Reality - my question isn't about load. not in the slightest. I have bigger loads coming ... ~5 years down the road. I don't know those in detail yet - but I"m more than happy and willing to rebuild a battery bank and move to 48V *at that time*. What I need to do is *get to 5 years down the road*. For the next 5 years, I am looking to hold up 2 people in a 25' trailer. We are using it for generally 3 days at a time, max. Daily consumption ~2-2.2KWh.

                          All the calculators I could run pretty much gave me a bank size of 600Ah. but getting this 804Ah bank turns out less expensive than the 6, and I don't have to parallel any batteries to do it - the 600Ah bank needs a lot of wires, big ones - and this bank only needs 2. That's a lot of stuff that I don't have to worry about. Also only 12 caps to check for water, compared to 24 if used 6V L16s.

                          My loads look like i should never exceed 20% DOD. I'm completely happy with that for the next 5 year window. Even if I've missed something stupid, and they go to 30% , I'm still happy; the battery bank is big enough to hold me up, and the input power SHOULD be enough to supply my *loads . 20% is ~4Kwh/day , if I did my math right; i'm only projecting half of that based on the stuff I have going into the trailer. So I'm pretty sure - for now, I left a lot of overhead.

                          What I don't know is if the 6x300Wh panels will be sufficient to run enough current into the battery bank to *charge* it effectively, because unlike calculating my loads or figuring out the amp draw, that number seems to be all over the map and its got me stumped. I"ve read that undercharging your batteries can be bad for them as well, and seen numbers indicating an ideal range; I"m not sure how to validate that I"m there specifically for current provided by array vs size of battery bank. I am putting a propane generator on, but obviously would like to minimize that use. If i need 2 more panels, good; if i need more than2 more, i'll spend the money on smaller batteries.

                          My math went 'assume 25% dod, thats 200Ah, thats about 4800Wh at 24v, lets not count on 7.8 , lets go with 5 on average for the days i'm going to be up there, and that gives me a panel size of 960 , lets use a factor of .6 for system losses, that gives me .. 1600. ish.'. So I think i can get sufficient power from teh 1800 watts of panel including system loss - but i'm still concerned that the incoming amperage might be low - do I NEED to get up to C/10 , or is a lower amperage inbound sufficient given the days of 'no use' in between our visits?


                          Comment


                          • #14
                            Originally posted by bcroe View Post
                            Seems to me regulations are going to require water, and you say your own well (pump). That in itself is
                            going to make it very difficult to be off grid. Do not forget, getting that motor started might take a peak
                            of 5 times running current. I suggest you design your project around this problem. At that point a grid
                            tie might start to look a lot more attractive.

                            I do not understand $120 a month for a meter, mine is only $15 USD. Bruce Roe

                            Pump is lake draw, 1/2HP, 5 feet above the water, maybe 25 feet of head, jet pump. 1650W worst case starting surge, measured on a kill-a-watt. I think I should be fine for it.

                            Grid tie is out of the question. $7,000 + 13% tax simply to get to ' There is a meter on the lot '. The utility charges punitive transport rates for seasonal-residences, meaning basically everyone in the area who doesn't live there as a primary residence gets creamed. I've gone through the power bills with a LOT of people. My best friend , 12 km up the road, regularly gets bills of $200 in the summer, and most of the summer , with a single 2-week exception, he's only there 2.5 days a week). And I'm not going to hold my breath for any of the local rates to go down. All in, this system is coming in under $9500 , taxes in. Less than the meter pull + one year of bills. Ok, I haven't put the price of the generator into that yet. Still, over 5 years, I don't see where this doesn't work as a good choice for me.

                            We aren't high-power consumers.
                            My monthly bill in the city - including transport charges, on a house with an electric dryer, and a not-great efficiency central air unit, is under $90. In Ontario, that's pretty good - and there are more of us in this house then there will be up at the lot.
                            I really don't have concerns about load or surge at this point - I think I'm ahead of the curve on that - and IF we end up where we are aiming 5 years out, well, I don't mind a redesign there, or a re-evaluation of 'on-grid' supply.

                            Comment


                            • #15
                              Originally posted by Droo71
                              Pump is lake draw, 1/2HP, 5 feet above the water, maybe 25 feet of head, jet pump. 1650W worst case
                              starting surge, measured on a kill-a-watt. I think I should be fine for it.
                              Your problem is greatly eased if you can use a very low head (and hp) pump. However I do not believe
                              my kill-a-watt (or yours) is capable of recording an instantaneous peak surge. And watts is not including
                              the additional reactive current of VA. Those numbers will set the minimum size inverter plant, in part
                              driving battery and solar requirements. Unless you want to build a throw away system just for now,
                              probably uneconomical.

                              Otherwise a battery plant-DC pump will solve any startup problems, batteries will still need a backup
                              generator and constant supervision, not to mention regular replacement. Bruce Roe

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