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  • #16
    it seems to make sense to me to start with the less variables, X amount of panels, produce X amount of power (factoring in location) and cost X amount of money, with that info i know what i can run and if its not enough try to increase my budget BEFORE i buy the wrong equipment
    I hear what you are saying, but its really the same thing, either you work configure a theroetical system, then look at what it will run, or look at what you want to run then configure a theoretical system then see if you can afford it.

    either way, in my view, the main thing is to understand how much it costs, and the lifestyle you need to lead to live on stand alone.

    People talk about stand alone as as alternative to mains power, its not, The breaker for mains power in a house in Australia is I think normally 60a, so you have that power avail basically, 24/7, you can plug in a welder, compressor and a heap of power tools, have the hot water boosting, lights, tvs, acs et etc all going at once. the only consideration you have is cost to use the power, its always there if you want it.
    To have that lifestyle on stand alone you would need a minimum 20ka genset on auto start and you would use a heap of fuel.

    You keep mentioning variables, and thats the hard bit for sure, friends come to stay, you have more lights on, the fridge and freezer are openmore, they bring portable fridges that they want to plug in etc etc.

    I had a bit ti do with stand alone before I bought my own system, thought i new a bit about stand alone, After living off a stand alone system for 5 years now I realize I new VERY little about it, I can tell you that If I new then what i know now there is no way i would have purchased a property without mains power.

    Thats why I often comment that living on stand alone is a pin in the but

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    • #17
      Originally posted by Sunking View Post
      Never mind I found it. Short story get your money back or buy another one.
      I don't quite understand why you would tell him to ask for a refund. I have the 6048 controller...It is a true MPPT controller. I have it running over a 100v stepping down to a 24v battery bank. It does step up the amps to get very close to the wattage produced at the panels into the batteries. Could you expound on your recommendation for him to return?

      Comment


      • #18
        Hi Bala,
        Many thanks for your reply, of course you are right, i think it is just that i have been going over hundreds of post over the last couple of weeks and what has struck me is that so many members start off with great intentions only to be shot down with technicalities and dissmissive replies, it must be because they come across as being, 'part timers' in alternative energy, or just stupid for thinking there little project's make a difference.
        I just think with all the knowledge and expertease (spelling!!) on these forum's there is no need for most of the replies to come down to that, no one wins, indeed we all suffer because people just think sod it, and give up on solar.
        You are right again about "OFF GRID" I live in Gambia for 3-5 months of the year, forget no power grid, water or sewage, i have spent two days trying to buy a replacement 6" saw blade, i could buy a new saw with a blade on it!! I ended up getting one sent with DHL from the UK.
        Same as you with " if i knew then ", but you are probably in the same boat as me for that, mine is approx 1.3 mil stirling, there is no return!! Just deal with what you got and the choices you made getting there.
        As i have said, I NEED HELP, and after looking at ALL of the post in the Off Grid section, and many other for fridges, pumps, etc most of the members just need help, not the SHORT or DISSMISSIVE answers, or the TECHNICALS JARGON replies that both I, and them have recieved.
        Bala, what you have learnt about off grid and your system is fantastic and the general day to day issue's are different for you as they will be for me but, over time like me you may have made some costly mistakes, i am about to build solar arrays for a whole village, it would be great to get people like Naptown there as, " he does it for a living" but, that will never work in Africa, i have seen millions of dollars worth of solar distroyed out there, (one for you Naptown). In November while in Gambia i was asked to look at a solar array that had been built by Gamsolar, (the owner is a Dutch man, and the biggest in Gambia) for a hospital that was also run by a Dutch lady for their charity, the first phase was built 4 years ago 18x175w panels on a tracking platform, and 5,280ah worth of batteries at 24v, yes 5280, after 2 years construction increased so the power supply had to increase but, they were informed there batteries were scrap 108,000 euros and needed to be replaced, they then built a fixed array of 16x175w 'UNDER' the first array, i am not joking, under the first array, and then supplied them 80x200ah deep cycle batteries, (they looked fantastic in the hot tin roof shed, mounted 4ft off the floor), the reason for the call to me 8 months later was, 'everything shut down at 2am', what do you do!!
        The largest array i will build 64 x 200w, i have tried to make it as maintence free as possible, but even then, (knowing you can only fix it when things go wrong) i have had, one of the young men from my youth foundation here in the UK for 3 months just to learn about the solar arrays we are building.
        Because of my time away and the lack of internet there, i have to cram all the info i can get while here, and then go straight into the field trial, PLEASE HELP. Mike.

        Comment


        • #19
          Originally posted by bidaw View Post
          I don't quite understand why you would tell him to ask for a refund. I have the 6048 controller...It is a true MPPT controller. I have it running over a 100v stepping down to a 24v battery bank. It does step up the amps to get very close to the wattage produced at the panels into the batteries. Could you expound on your recommendation for him to return?
          Simple it is completely inadequate to do the job he wants it to do.

          It is a MPPT controller, but 1 of the worse designs I have ever encountered. Well it is not the design, the Fairy Tale Claims of the manufacture. I will try to explain.

          Lets take its maximum input ratings, and compare with output ratings. It does not add up to the claims.

          MPPT Range @ System Voltage = 16/32/48/64~112VDC@12/24/36/48V

          OK this tells you the input Vmp voltage vs battery voltages with 112 volts is the max Vmp voltage the unit can handle. Ignore Voc as it is useless other than cold temp coefficient. 112 volts Vmp is the max. For a 12 volt battery system they are saying to run 16 volt Vmp panels, and for 48 volt systems run 64 volt Vmp panels. That is fine and dandy.

          Max PV Input Current = 40A
          Max Charging Current = 50A This is the max output current.

          OK this is just fine until you run some numbers. Let's go to the extreme and say we want to run the panel Vmp up to 112 volts. Power = Volts X Amps. So 112 volts x 40 Amps = 4480 watts.. So the output current on a 48 volt battery has to be 4480 watts / 48 volts = 94 amps. It has a maximum output of 50 amps.

          Let's go to the other extreme using their recommended specs for a 12 volt system. Input = 16 volts x 40 amps = 640 watts. Therefore on a 12 volt battery the output has to be 640 watts / 12 volts = 53 amps. OK I buy that. On a 12 volt system the maximum input wattage is 640 watts. Far from the 3400 they claim.

          Lets now go back to the high extreme working reverse to find the maximum at 48 volt batteries. To find the maximum power inout take th e48 volt battery voltage and multiply it by the maximum charge current output and you get 48 volts x 50 amps = 2400 watts.

          So the specs are make believe. There is no combination that would allow for a 3400 watt input. The true ratings for this controller are a 50 amp MPPT controller with a maximum wattage input vs battery voltage of

          600 watts @ 12 volts.
          1200 watts @ 24 volts
          1800 watts @ 36 volts
          2400 watts @ 48 volts.

          Using conventional 12 volt panels, with 4 in series to make a 48 volt system the input would be roughly 64 to 70 volts @ 40 amps input is all it can handle (2400 watts) That would yield an output of 48 volts @ 50 amps.

          Math does not lie. People lie. All you got to do is listen to the numbers, not the claims.

          Here is the simple math to figure out the max input wattage. Output Current x the Nominal Battery Voltage. We know the variables. The output current is fixed at 50 amps. The battery voltages are 12, 24, 36, and 48 volts. Do the math.

          50 amps X 12 volts = 600 watts
          1200 watts
          1800 watts
          2400 watts.

          A 5th grader can do it.
          MSEE, PE

          Comment


          • #20
            Hi Bidaw,
            i have only just seen your post (check the time) as i was replying to Bala, (these post can take a while if you are new to this), i dont know how to create links or highlight other post's, but THANK YOU, i have spent many months on trying to buy, what will work out in Gambia, it is only for our basic needs, lights, more lights and maybe one or two freezers.
            As i have lear'nt in Africa, for me to start with consumption its nuts!! I have to look at what works first and then budget and then consumption (I challenge anyone to work that mother out and have time to run a business in the UK), OK my choice! But i spoke to the suppliers in South Africa, they have hundreds of customers like you Bidaw who are using these controllers, yes against an 'Outback' or 'Zantrex' they are inferior, however for the cost of one Outback i can buy almost three pcm5048, for me, thats allot of backup, and believe me, that is the one thing you need in Africa, I thought i had brand new Stainless Steel cutlery, still in there packing, shipped out in June of last year, i opened the boxes in November, full of rust, one boy 4 hours to clean a 12 piece set.
            Sorry for the diversions, i am only trying and get some understanding of the country for those who have not been there. My original post is still a valid one!! I have, panel voltage, string voltage, VMP voltage, VOC voltage and battery bank voltage, what do use for the calculation to make sure i do not overload my charge controller, (pwm or mppt) now i am not sure.
            Sunking, can you please explain yo brief answer?

            Comment


            • #21
              Hi Sunking,
              Thankyou for replying, as i have said before i am not sure how to bring in quotes so i will just ask the question to your reply if thats ok.
              Firstly, i have looked closley into the company who build these controllers, one of my main criteria's was to run as high a voltage as possible because of the climate and cable size, they recomended this controller, if using lower voltage as you like to quote, they would have recomended another controller.
              You first told me, I got real bad news for you my friend. Your charge controller is not going to work period. With a 40 amp MPPT controller the maximum panel power input vs battery voltage is:

              500 watts @ 12 volts
              1000 watts @ 24 volts
              2000 watts @ 48 volts.
              Now you state that it is simply inadequate, so your first assumption was wrong, YES!!
              You also seem to forget in your last assumption about the Max input power of 3400w
              Why would you do this ?
              When you said in your first post to me, 'your controller is not going to work period!' That alone gave me a butterfly stomach.
              You then told me to use 'nominal battery voltage @48v' is that correct for a mppt controller, which, as you NOW agree is what i have purchased, not sure where, 'i see said the blind man, etc, you have a pwm controller'

              Your quote; OK this is just fine until you run some numbers. Let's go to the extreme and say we want to run the panel Vmp up to 112 volts. Power = Volts X Amps. So 112 volts x 40 Amps = 4480 watts.. So the output current on a 48 volt battery has to be 4480 watts / 48 volts = 94 amps. It has a maximum output of 50 amps.
              I do not have 40amps, why are you using that figure? And the limit for the controller is still 3400w, please go back and look at my orignal post.
              As for the 12v extreme, you and many others have stated that over a certain wattage you should increase the voltage to be more efficent, is that also not true now??
              your quote; Lets now go back to the high extreme working reverse to find the maximum at 48 volt batteries. To find the maximum power inout take th e48 volt battery voltage and multiply it by the maximum charge current output and you get 48 volts x 50 amps = 2400 watts.
              I agree with the calculation but, is that how a MPPT controller works? The last thing i need is to get tied up with 'holier than thow attitudes'. As i have said many times I NEED HELP, not assumptions, not variables, just facts for what i am trying to do, if i need additional controllers for these arrays, as stated, i have extras, however if i can get the right answer to my first post, i may be able to use the additional controllers to other people lights.
              Many thanks Mike

              Once again you

              Comment


              • #22
                Sorry Sunking,
                I have just gone over your last post again, and quite simply you are WRONG, you have completely ignored the manufacturers specification, if i was to do that with all the controllers available, i too could have the same results, it proves NOTHING. I am not sure why you would do it apart from trying to cover your mistakes in the earlier post. I have no doubt your have allot of authority in this forum, and will probably get all of these post removed, but as i have said many times, I would like some help.

                Comment


                • #23
                  i participate in a few forums of different types and have few rules I go by,

                  what needs to be remembered is that it is a forum, its free information and there is no gaurentee that what anyone claims or says is true.

                  I dont take any info I get on a forum for granted i use in as a tool along with other research to learn what i want to know.

                  "can do cant teach" just because someone is good at something does not mean they can get there message across to someone else.

                  generally speaking people dont read posts properly or they cherry pick, reply to one line so the reply is out of context,

                  or simply dont get what you are trying to ask,

                  I have found to get the best results ask basically one line questions, get the answer to it do other research on the answer if needed then move on,

                  gambia lodge, I can understand your frustration, I work in remote area, no shops etc etc,

                  The camp where I live has no RCDs or ELCBs fitted, we have two onsite elctricians who are not familiar with RCDs so i am orgainsig to fly an electrician from Australia in to sort it out, along the lines of $1000aud a day for labour + air fares and accom, business in a remote area is expensive.

                  I am a mechanic thats what I get paid to do, on the mechnical forums I post on I can often help people, but its not my job i dont get paid to do it, sometimes i cant be bothered or I am to busy and i also dont take for granted that some will help me with my problems.

                  you have obviously invested a lot of money in this project, BUT, at the end of the day you are running a commercial enterprise, its was your decission to project manage the solar instalation rather than pay some to design and install it,

                  i think its a bit rough for you to critisize the replys you get on a free forum,

                  Comment


                  • #24
                    Originally posted by Gambia river lodge View Post
                    Now you state that it is simply inadequate, so your first assumption was wrong, YES!!
                    You also seem to forget in your last assumption about the Max input power of 3400w
                    Why would you do this ?
                    When you said in your first post to me, 'your controller is not going to work period!' That alone gave me a butterfly stomach.
                    My first assumption was your controller was PWM. I made that assumption because of the Model Number. That is why I asked you for a link to the spec. Things were not adding up. MPPT charge controller are not spec to input current. Only PWM controllers spec input current. MPPT controllers spec output current. Your is 50 amps.

                    Regardless whether or not it was PWM or MPPT, I was certain and still certain it will not work for the way you intend to use it. Put very simply it is TOO SMALL.

                    The unit is a 50 amp MPPT charge controller period. To quickly determine the maximum amount of panel wattage any PWM controller can handle is very simple. Multiply the current rating by the battery voltage. Makes no difference if the panels are wired for high or low voltage. So you are using 48 volt batteries right? Maximum panel wattage you can run is 50 amps x 48 volts = 2400 watts.

                    You can certainly connect 3200 watts of panels to the input. Will not hurt a thing because the controller will limit the input and only use 2400 watts of the 3200. So you end up wasting 800 watts of panels for nothing.

                    You have two options:

                    1. Buy another one of the controllers you have now, and divide you solar panels into two separate 1600 watt arrays each with its own charge controller, and them connect the two charge controllers to a common 48 volt battery.

                    2. Buy a 80 amp charge controller.

                    Where you are going to with this system, quit worrying about 140 VOC. Extreme cold is not an issue. With your charge controller it is the Vmp or voltage at maximum power you is what have to worry about, not Voc. It is stated right there in their specs. The maximum Vmp your charge controller can handle is 112 volts period. All you have to worry about is keeping the VMP voltage above 64 volts (for a 48 volt system), and below 112 volts.
                    MSEE, PE

                    Comment


                    • #25
                      Originally posted by Gambia river lodge View Post
                      Sorry Sunking,
                      I have just gone over your last post again, and quite simply you are WRONG,
                      No I am not wrong, I am spot on with my answer. The specs you gave at first are incorrect. Not your fault because the manufacture is wrong.

                      I am going to say this one more time. MPPT charge controllers current rating are specified by the OUTPUT, not input. Your controller is 50 amps.

                      [URL="http://ELECTRICAL SPECIFICATIONS MPPT Range @ System Voltage 16/32/48/64~112VDC@12/24/36/48V Max PV Input Voltage 140VDC (Open Circuit) Max PV Input Current 40A 70A Max PV Input Power 3400W 5400W Recommended Battery Type Flooded, GEL, or AGM Lead Acid Nominal Battery Voltage 12/24/36/48V Max Charging Current 50A 80A Standby Power <2W Charging Schemes Bulk, Absorption, Float, Auto/Manual Equalization Battery Temp. Compensation Built-In, -5.0mV/
                      MSEE, PE

                      Comment


                      • #26
                        Originally posted by Sunking View Post
                        I am going to say this one more time. MPPT charge controllers current rating are specified by the OUTPUT, not input. Your controller is 50 amps.

                        Your controller can only input 2400 watts maximum with a 48 volt battery system.

                        If you do not believe me, wait for other answers from someone else. But if they know what they are talking about, they will tell you the same thing.

                        Sunking is correct. Your controller, while it is MPPT...it is limited by the charge current. You just have to be aware of that when sizing your system. The good thing about the controller that you have, it will parallel charge with additional controllers. From the way you describe, you should have plenty to do so. Make sure you size your panel input not to exceed your calculated output for each controller and you will be fine. If the 50 amp output is too limiting for your application, contact MPP Solar directly - Peggy (that is who I dealt with in purchasing), They will most likely take your existing controller and credit you toward an upgrade to the 80 amp controllers if you need to bump it up. Either way, if you know what you have going into it...you will be happy with the controller. It really is an inexpensive alternative to the Outback, Midnite, etc... because 1. it is true MPPT and 2. the brief but accurate education that Sunking just gave us on rating a MPPT controller. My 6048 has served me well in my 24v setup, mainly because I am not upside down in my input to output ratio. - It does work in the spec range that he (Sunking) laid out to the T!

                        Comment


                        • #27
                          There are many ways for a charge controller to "claim to produce" MPPT function. Sadly, plasmatronic does a poor job, and has "inventive" ways to put numbers on their poorduct.

                          Sunking is right, you will need to have another charge controller to get the most power out of your system. His language is curt/abrupt but his math is very right.
                          Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                          || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                          || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                          solar: http://tinyurl.com/LMR-Solar
                          gen: http://tinyurl.com/LMR-Lister

                          Comment


                          • #28
                            There are many ways for a charge controller to "claim to produce" MPPT function. Sadly, plasmatronic does a poor job, and has "inventive" ways to put numbers on their poorduct.
                            Not sure if it makes any difference? but plasmatronics do not make MPPT, they only have PWM

                            Comment


                            • #29
                              Hi all,
                              Thanks for your replies, i am currently eating 'Humble Pie' and sincerely apologize to anyone i have offended, especialy 'Sunking', most of you will be aware that using this forum is still very new to me, this is not an excuss and i logged into this forum today after reading 'Bala's reply in my email in box to say, i take everything onboard he says, and to say sorry for any offence caused.
                              It was a very pleasant suprise to read the additional replies after 'Bala' pointing out i was 'out of order'. Thankyou 'Sunking' i felt pretty sure that was the end of me and this forum.
                              Your are right again 'Sunking' i was designing my system on the information i was given buy the suppliers, and unfortunatley the panels i have do not list VMP on them which is why i asked the first question, "what voltage do i use", My first concern was not to overload the controllers on the 'input side', using the 'values' supplied it looked ok however, i still had a gut feeling that something was incorrect, like many suppliers of MPPT controllers, they push the fact that they are not 'voltage specific' they adjust the input voltage to whatever battery bank size you wish to use, (almost forget that part) stupidly i ignored that side of the system, and was only concerned with overloading the equipment on the input side of the array.
                              I do have an additional 4 x pcm6048 controllers, the ratings are different to the pcm5048, Bidaw, would you know if the two different units can be parralled ?
                              Once again, thanks for your replies.

                              Comment


                              • #30
                                First no need to apologize, its a forum so do not let anyone offend you. Only people I know and trust can offend me. Otherwise I do not give a darn what people think. As for me I shoot from the hip and hit hard. Not to offend, but get your attention to something important. If you read between the lines of what I say, you can pick up the humor I offer.

                                Do you know the panel model number? I bet I can find the specs if I know the manufacture and model number. Any reputable panel manufacture has to supply:

                                Voc
                                Vmp
                                Isc
                                Imp
                                Pmax
                                Temperature Coefficient.

                                Otherwise there would be no way to design a system, nor could they be listed, certified or pass inspections in a code compliant system...

                                As for cascading or paralleling the charge controller you have, YES they can be paralleled as stated in their specs. All you need is the com port cable to allow them to communicate and load share.

                                FWIW, for as long as I have been around here, the MODS are not going to pull the plug on you for a passionate spirited debate. If they did, I would have been gone long ago.
                                MSEE, PE

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