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Putting a Small Solar System on a shed (or awning) to Charge an Electric Car

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  • #16
    Seems a lot of effort for only a possible three hours of charging time.

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    • #17
      What state are you in and what are the rate offerings for EV charging? How much do you charge your EV per week in kWhrs or miles of range added by charging?
      9 kW solar, 42kWh LFP storage. EV owner since 2012

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      • #18
        so many negative comments! I think I will take these questions to the facebook group DIY powerwalls because at least there is a community there who likes to play around with electronics. First, I have an EE degree (ok that was 30 years ago) so this is not really over my head. I do have a friend who can help with this, actually I do need to call him for advice.

        To answer the question from Ampster: I am in Massachusetts and I am not aware of any time of use regs though they may be coming. The number of KW hours we charge the EV right now is about 15. In the future it could go up.

        There is room for 2 more panels on the roof, but I don't think I can modify the existing system. Current system has 3 sets of 6 panels wired in series (38 volts is the output of each panel, and the panels have microinverters). I have a 4.8Kw system. The lease can't be bought out until 2023.

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        • #19
          Basically, the question is this. Should I purchase a small PV system to charge a battery that will be used to partially charge another battery when I already have utility power readily available and all this under the guise of saving the environment with an electric car? Seems like one of those rhetorical questions where everybody should already know the answer.
          Dave W. Gilbert AZ
          6.63kW grid-tie owner

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          • #20
            Originally posted by leftlink View Post
            so many negative comments! I think I will take these questions to the facebook group DIY powerwalls .......
            These are not negative comments. There are many questions that are being asked. Questions and answers are a requirement to design a good system. There are many very knowledgeable folks here wanting to help you, give honest real life answers and not just stroke your ego.

            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

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            • #21
              Originally posted by leftlink View Post
              so many negative comments! I think I will take these questions to the facebook group DIY powerwalls because at least there is a community there who likes to play around with electronics. First, I have an EE degree (ok that was 30 years ago) so this is not really over my head. I do have a friend who can help with this, actually I do need to call him for advice.
              Yes, I have experienced the same. There are certain niche levels of expertise here. With your skillsets and access to other forums you should be able find some solutions. There is also a diysolarforum that is fairly new that has a lot of DIYers. See one idea below.
              To answer the question from Ampster: I am in Massachusetts and I am not aware of any time of use regs though they may be coming. The number of KW hours we charge the EV right now is about 15. In the future it could go up.

              There is room for 2 more panels on the roof, but I don't think I can modify the existing system. Current system has 3 sets of 6 panels wired in series (38 volts is the output of each panel, and the panels have microinverters). I have a 4.8Kw system. The lease can't be bought out until 2023.
              You could look at the existing NEM agreement to see how much additional production capacity you could add. In California my agreement with the power company allows me to add 1kW in power. I did that on a separate circuit with micro inverters because my main system is under warranty with the installer. I bought four used Sunpower panels and micro inverters for less than $1000 ($1 per Watt). All I needed was a building permit, another circuit breaker and some wire. I have started charging my EVs part of the time during the day because of some changes in the TOU time periods that were not beneficial.
              9 kW solar, 42kWh LFP storage. EV owner since 2012

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              • #22
                Originally posted by Ampster View Post
                You could look at the existing NEM agreement to see how much additional production capacity you could add. In California my agreement with the power company allows me to add 1kW in power.
                Thanks, this is interesting. I have an interconnection agreement but it does not really reference what can be added. There is a state guideline that I should not exceed 100% of usage and right now I am at around 85%. If I add generation then would the solar lease company (NRG) see the additional production? I don't know if the power company really has any rules regarding what I generate, except that if I have a surplus that builds up, I don't have any way to get the money back.

                I have attached a few excerpts from the interconnection agreement I signed about 4 1/2 years ago as the system was about to go online. So you are suggesting I could add panels somewhere in the yard and then run a power cable to my electrical panel? This is all new to me, I was not aware that such a thing was possible and i was thinking that the power from panels to my existing solar monitoring box (Locus) was greater than 240 volts. If you can explain why there isn't anything required between your microinverters and your breaker it would help me understand this a bit better!
                Attached Files
                Last edited by leftlink; 07-24-2020, 06:00 PM.

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                • #23
                  Originally posted by leftlink View Post

                  Thanks, this is interesting. I have an interconnection agreement but it does not really reference what can be added. There is a state guideline that I should not exceed 100% of usage and right now I am at around 85%. If I add generation then would the solar lease company (NRG) see the additional production?
                  Not if it goes to a separate breaker. You probably should refer to the lease agreement to see if there are any restrictions.
                  I don't know if the power company really has any rules regarding what I generate, except that if I have a surplus that builds up, I don't have any way to get the money back.

                  I have attached a few excerpts from the interconnection agreement I signed about 4 1/2 years ago as the system was about to go online. So you are suggesting I could add panels somewhere in the yard and then run a power cable to my electrical panel? This is all new to me, I was not aware that such a thing was possible and i was thinking that the power from panels to my existing solar monitoring box (Locus) was greater than 240 volts. If you can explain why there isn't anything required between your microinverters and your breaker it would help me understand this a bit better!
                  Unless your installer did something different the only thing would be a combiner box between the microinverters and your existing breaker. That just combines the inverter wires in parallel.
                  To do what I am suggesting would require a building permit and it would not be easy to find someone to install a small system so you are looking at doing it yourself.
                  9 kW solar, 42kWh LFP storage. EV owner since 2012

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