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  • Upgraging Solar System, Some Advice Please.

    Hi All,

    I'm looking into buying a completely new solar off-grid set up as mine has just about had its day, the batteries on my existing set up are now well over 11 years old and need "genny" help to get to "float" stage even with a good 4 to 5 hrs peak sun day.

    I had read Sunking's sticky regarding set up and just wanted to run a questions by you.

    1 - I have worked out that I will be looking for 5200 watt hours as daily usage.

    2 - With Fudge Factor of 1.5, it converts to 7800 watt hours.

    3 - I'm going to use 5 hours peak sun as an average due to location of southern Spain.....(Prepared to compensate with a back up generator for winter reduction).

    4 - Panels need to be 1560 watts.....(7800w/5hrs).

    5 - System option would be 24v......(between 601w to 2000w).
    Battery req. 5200w x 5 day autonomy = 26000 watt hours
    26000w/24v = 1083 Ah battery capacity.

    6 - Charge Controller req. 1560w (panels)/24v = 65 amps.

    Sunkings example indicates either 20% DoD or 5 day autonomy if I have understood correctly, there are a few methods of system sizing available on the web, some appear to advocate both.

    As you can tell I am a novice as far as solar goes even though I have used it for 11 years, I just don't seem to able to do "technical"
    I am intending to get at least 2 quotes using my daily usage, my real question is....am I far off the mark with what I have illustrated above as to what my requirements should be.

    I would like to invest in some quality batteries, Rolls seem to be one of the better makes available here, panels have reduced greatly in price over the last 10 years and Rec seem to offer a decent panel (I have room for 8 panels if needs be). I have a FlexMax60 charge controller on my current system although the above workings seem to suggest ideally that 65 amps is required, will I need to upgrade to a Flex80?. Lastly, some advice on an inverter would be appreciated as it is not included as far as I can see on the example.

    Many thank and sorry it's a bit long winded,

    Mike........(Sunny Spain...atm).

  • #2
    Originally posted by mikeyj View Post
    Hi All,

    I'm looking into buying a completely new solar off-grid set up as mine has just about had its day, the batteries on my existing set up are now well over 11 years old and need "genny" help to get to "float" stage even with a good 4 to 5 hrs peak sun day.

    I had read Sunking's sticky regarding set up and just wanted to run a questions by you.

    1 - I have worked out that I will be looking for 5200 watt hours as daily usage.

    2 - With Fudge Factor of 1.5, it converts to 7800 watt hours.

    3 - I'm going to use 5 hours peak sun as an average due to location of southern Spain.....(Prepared to compensate with a back up generator for winter reduction).

    4 - Panels need to be 1560 watts.....(7800w/5hrs).

    5 - System option would be 24v......(between 601w to 2000w).
    Battery req. 5200w x 5 day autonomy = 26000 watt hours
    26000w/24v = 1083 Ah battery capacity.

    6 - Charge Controller req. 1560w (panels)/24v = 65 amps.

    Sunkings example indicates either 20% DoD or 5 day autonomy if I have understood correctly, there are a few methods of system sizing available on the web, some appear to advocate both.

    As you can tell I am a novice as far as solar goes even though I have used it for 11 years, I just don't seem to able to do "technical"
    I am intending to get at least 2 quotes using my daily usage, my real question is....am I far off the mark with what I have illustrated above as to what my requirements should be.

    I would like to invest in some quality batteries, Rolls seem to be one of the better makes available here, panels have reduced greatly in price over the last 10 years and Rec seem to offer a decent panel (I have room for 8 panels if needs be). I have a FlexMax60 charge controller on my current system although the above workings seem to suggest ideally that 65 amps is required, will I need to upgrade to a Flex80?. Lastly, some advice on an inverter would be appreciated as it is not included as far as I can see on the example.

    Many thank and sorry it's a bit long winded,

    Mike........(Sunny Spain...atm).
    Mike I believe you have done the math correctly.

    To make sure you do get enough power generated by the sun I would go with an 80A CC and up to the maximum input wattage for it. You are probably looking at ~ 2000 watts of panel which would be 8 x 250watt type.

    Also with 80Amps of charging your battery system should be no larger than 1000 Ah to stay within that C/12 minimum charge rate.

    You did not mention the type of inverter you are currently using or what your loads are but I would estimate that you should be using a pure sine wave type inverter rated 24v at around 2000 watts max.

    Comment


    • #3
      Hi SunEagle,

      This is the first time I haven't sounded like a complete wally on this forum, I'm chuffed to bits, I'll probably fall down a well or something tonight if I keep gloating.

      Thanks for the confirmation, I'll be better armed for the firms coming round for the quotes.

      Yes, sorry.....I'm currently running the system with a 3kw pure wave invertor on a 24 volt set up.

      I was also hoping that somebody would recommend going a little over on the panels, especially as I already have the space.

      Many thanks,

      Mike.......

      Comment


      • #4
        Hola Guys,

        Well, I've had a local company out to give me a quote for a completely new solar system. I gave them my daily watt hour usage figure of 5.2kw hours for the house and garage usage and asked for a quote for a separate DC system to run our swimming pool using a solar pool pump etc, with the possibility of diverting some power back to the house set up during the winter months when the pool was to be covered and only run to stir some chlorine around.

        I was informed that it would be a better bet to go for a more powerful overall solution/system which would be capable of running the pool comfortably during the summer months and having the extra power in the winter months to basically compensate for lesser sun hours. Hope that made sense.

        The suggested system was:-

        1 x Victron Multiplus 24/5000/120-50 Charger/Inverter

        2 x Victron Charge Controllers MPPT 150/70 (12/24/36/48v-70a)

        12 x Eurenar 250w Solar Panels AAA grade

        12 x 8 OPzS800 2v Batteries (900Ah@C10)

        They recommended sticking to my current 24 volt set up, even with 3kw of PV array?

        I appreciate that some of the makes may relate more to the Spanish market (Victron are Dutch manufactured and are better than Outback "allegedly".


        I get the feeling that this system is way over the top even running a pool in the summer for 6hrs....(2 charge controllers for efficiency??). I thought that it would be better to keep the pool as a separate system personally and have a better tailored system for the day to house house and garage system.

        What do you guys thinks from the info I have given you?

        Look forward to hearing from you,

        Mike.

        Comment


        • #5
          If I was going to have a new off grid system , my list wold be like this:
          Victron multiplus 48/3000/ with 2 150/35 mppt's integrated
          24 OPZs6 hoppecke
          10 panels 250wp
          That would give me about 4300wh a day with 4-5 days autonomy.
          A new system for that size I would go for 48v .

          Comment


          • #6
            Hi Raul,

            Thanks for the reply, I too would have thought it more prudent to go for a 48 volt system overall, this is why they are recommending 2 x charge controllers @70amps then, because my new panel wattage would be 3000 watts. My basic understanding from what Sunking has explained is that the battery capacity would be halved using a 48 volts set up.

            I wanted a little flexibility with this new set up and am prepared to use decent equipment, but didn't want to pay over the odds for shed loads of power if there was really no need.

            Mike.

            Comment


            • #7
              You don't half the capacity ; double the voltage half the amps. The watts are the same . Going 48v you need half the amps vs of a 24v system and becomes safer and more efficient.

              Your biggest cost will be batteries . The once I suggested can take a 2.5kw array. Rolls are good but extremly expensive anywhere in Europe.

              Comment


              • #8
                Your list in post 4 will barely give you 2 days autonomy.

                Comment

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