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  • New to solar system building off-grid

    Hello all - thanks for having such a great forum. I am sorry if this has been covered already but I have been reading for a week now and am still not sure if my set-up is going to work. I am trying to upgrade my father-in laws system so that we can use the off-grid solar at the cabin for more and use the generator less.

    I have calculated we need around 3000 watt/hours per day, most likely a bit less for on the average (LED lights, ceiling fan, toaster oven in morning, car stereo for music). The panels get about 6 hours of sun each day without much shade on it (sunshine coast in British Columbia)

    Currently we have 2 300W, 32.5v solar panels wired in series.
    MPPT controller - 50A, 12/24V, 150V
    4 6v golf cart batteries wire in series for 24V system
    Honda gas powered generator

    Planning on purchasing a 4000w inverter/charger with hook up to the generator for charging if the batteries get too low.

    As I am having a hard time with all the numbers and charging, not sure if the system is enough to run what we need and if not what do I need to change.

    Thanks for the help in advance

  • #2
    Welcome to the forums.

    First off, I'm going to tell you that your toaster oven is going to kill you. It draws way too much to be usable on a solar setup.

    How did you figure out your 3000Wh number? Break it down for us. What devices at what wattage for how long.

    Also, what is the parasitic losses on the inverter you're planning to use. There will be a published number (somewhere around 50W) that days how much it costs to have the inverter powered on and not doing anything.

    What batteries do you have? Specifically the type and amp hour capacity.

    What angle and what direction are the panels facing?

    if you're dead set on 3000Wh, then you are going to need many more panels. What seasons are you planning to use the cabin?

    Let us know that and we can really help you out.

    For reference, I'm currently running 2x300W panels and a bank of 4x 235Ah golf cart batteries to run my mini fridge and some lights/phones for the few days at a time that I'm at my cabin in the Caribou. I only needed around 860Wh iirc. But want to use it in the spring/fall, and have a few days autonomy when the sun hides
    ​​

    Comment


    • #3
      I thought the toaster oven could be a problem - here is the breakdown that I got from a calculator:

      Toaster oven - 600w for .5hr, 2 ceiling fans for 5hr - 1200w, 15 led bulbs 40w equivalent for 2hrs - 300w, smartphone/tablet recharge for 4 hours - 60w, laptop for 2 hours - 200w. All totaling 2,356 whours/day. With efficiency loss approximately 3000whours/day

      I have not purchased the inverter yet so not sure what the parasitic loss would be?

      I am not 100% sure as the batteries are at the cabin but they are golf cart batteries, deep cycle and I am pretty sure they are 200 amp/hours (I know not knowing for sure doesnt help, sorry)

      My father in-law set the panels up so not sure on the angle but they are north west facing

      Hope that all helps

      Comment


      • #4
        Originally posted by Azen-1
        15 led bulbs 40w equivalent for 2hrs - 300w
        150 w X 2 HOURS = 300 wHOURS, fix your units so we can communicate. You best use propane for
        cooking and heat, unless you want to always run the generator for those. Bruce Roe

        Comment


        • #5
          Sorry I am just using what the calculator I am using has given me.

          And in regards to heat, cooking etc it is all propane so do not need to worry about any of that just what we are trying to use the solar system for

          Comment


          • #6
            The cooking he was referring to was the toaster oven. I'd drop that off your list because it's a doozy.

            North Western facing panels is a tough blow to your system as well. You're not going to get anywhere near full power from the panels for most of the year. If you can find a better place to mount panels, is suggest moving them. If not, and you really want to continue upgrading, you might look into a ground mount system.

            I'd take a hard look at if you really need all the fans, lights, gadgets. Trim what you can.

            Read the sticky posts in the off grid section and get to know all the details in there. Learn what all the different units of measurement are, and what they mean. It's important for clear communication, and bugs a lot of people.

            For quick reference, your battery bank (going with the 200Ah assumption) is 24V x 200Ah so that's 4.8kWh of storage.

            If you want to use 3.0kWh of energy daily, you're not going to be able to do it with what you have. You need a ground up redesign. This is where reading the stickies will be helpful. You need to address the depth of discharge topic for your batteries. You don't want to use up more than about 20 % of your capacity per day. Otherwise you'll be down and out on the first cloudy day.
            ​​​

            ​​​

            Comment


            • #7
              If you want to use the cabin more and use the generator less, start by getting rid of the electric toaster.

              Then, get the panels at a more southerly orientation.

              Do you intend summer, winter or year round use ?

              Depending on weather patterns, azimuths between 90 and 270 degrees are OK with between 135 and 225 deg. much better. Azimuths facing north of 270 and 90 deg. azimuths are PV performance killers. See PVWatts, read the help screens and make a few runs to see relative performance as f(panel orientation) for an education.

              For best summer PV performance make the tilt ~ (latitude -15) deg. or so. Winter (lat. - + 15 deg.). Best tilt for year round performance is ~ at local latitude.

              Welcome to the neighborhood.

              Comment


              • #8
                Appreciate all the help - I am going to sit down and start re-designing the system. We only use the cabin in the summer months so only used for 3-4 months but will everything we want to run we either need to trim a lot of beef up the system.

                Thanks again and I am sure you will hear from me again

                Comment


                • #9
                  Originally posted by Azen-1 View Post
                  Appreciate all the help - I am going to sit down and start re-designing the system. We only use the cabin in the summer months so only used for 3-4 months but will everything we want to run we either need to trim a lot of beef up the system.

                  Thanks again and I am sure you will hear from me again
                  When I was a kid, I spent time in the summer w/better heeled relatives who had a cottage on one of the finger lakes in upstate NY that was used pretty much full time in the 2-3 months of summer. Pretty neat place for a kid. There was running water and indoor plumbing - just barely, but adequate - and electricity, but no TV and otherwise pretty sparse w/old furniture, etc., which seemed just fine normal given that it was quite rural. Your toast saga made me remember bitching about how long it took to make toast in the broiler section of a propane fired oven and being told to count my blessings. Little did I know. Thanx for jogging my memory.

                  Comment


                  • #10
                    My wife and I have an off-grid 'cabin' and designed the system based on the feedback from the folks here. I totally agree that propane is what powers anything that generates heat.
                    For the toaster, we use a cookie sheet in the propane oven (works just fine) but even a propane oven can use a fair amount of electricity to heat the glow plug igniter. I did consider an off-grid range (no glow plug) but they didn't really look very stylish.

                    If my wife wants to blow dry her hair, she has to ask

                    I can send you my spreadsheet of all my loads. The largest being water pump but there's tricks for that depending on how far you want to go....

                    PM me if you want spreadsheet and calculator formulas from this site.
                    Fridge and UV water filter are the other top consumers of power....

                    Comment


                    • #11
                      Originally posted by Riley5781 View Post
                      My wife and I have an off-grid 'cabin' and designed the system based on the feedback from the folks here. I totally agree that propane is what powers anything that generates heat.
                      For the toaster, we use a cookie sheet in the propane oven (works just fine) but even a propane oven can use a fair amount of electricity to heat the glow plug igniter. I did consider an off-grid range (no glow plug) but they didn't really look very stylish.

                      If my wife wants to blow dry her hair, she has to ask

                      I can send you my spreadsheet of all my loads. The largest being water pump but there's tricks for that depending on how far you want to go....

                      PM me if you want spreadsheet and calculator formulas from this site.
                      Fridge and UV water filter are the other top consumers of power....
                      There are no PM's on this forum.

                      Comment


                      • #12
                        Originally posted by Xplode View Post
                        Welcome to the forums.

                        First off, I'm going to tell you that your toaster oven is going to kill you. It draws way too much to be usable on a solar setup.

                        How did you figure out your 3000Wh number? Break it down for us. What devices at what wattage for how long.

                        Also, what is the parasitic losses on the inverter you're planning to use. There will be a published number (somewhere around 50W) that days how much it costs to have the inverter powered on and not doing anything.

                        What batteries do you have? Specifically the type and amp hour capacity.

                        What angle and what direction are the panels facing?

                        if you're dead set on 3000Wh, then you are going to need many more panels. What seasons are you planning to use the cabin?

                        Let us know that and we can really help you out.

                        For reference, I'm currently running 2x300W panels and a bank of 4x 235Ah golf cart batteries to run my mini fridge and some lights/phones for the few days at a time that I'm at my cabin in the Caribou. I only needed around 860Wh iirc. But want to use it in the spring/fall, and have a few days autonomy when the sun hides
                        ​​
                        What CC are you using for this setup ? Series ?Parralel ?
                        I currently have a VictronConnect 30 amp MPPT on the West Coast and want to use almost the same size panels.

                        Comment


                        • #13
                          Originally posted by baddancer View Post

                          What CC are you using for this setup ? Series ?Parralel ?
                          I currently have a VictronConnect 30 amp MPPT on the West Coast and want to use almost the same size panels.
                          I'm using an EPever Tracer 4210AN charge controller for my setup. The 2 panels are in Series at around 72Volts.

                          Comment

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