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  • I just discovered panels will get shade, change build?

    I've been thinking for a while of throwing solar panels on the roof of my detached garage. A small installation, mainly to tinker/get started with solar - grab 4 used 300 watt panels locally, connect them in parallel, add a MPPT charge controller, a 12v battery system, an 12v inverter and call it a day. Yesterday I discovered my neighbor's house starts shading my garage roof around 3:00 PM and when it's completely shaded there's still about 2 hours of sun left in the day. I hear partially shaded panels can dramatically decrease the power output of the whole set and/or cause the non-shaded panels to over work and over heat. Being this is a small, no so serious project, what changes would I need to make to compensate the gradual shading this set of panels will get and still get some energy from them.

    P.S. - The roof of the house (main building) is higher and is unblocked so it gets full sun all day. I will have solar professionally installed on that roof some time in the future when I'm ready to go all in. Plus the house's roof has a steeper pitch which isn't safe for me to be up there myself (and I'm afraid of heights). I can easily get on the garage roof, so that's why I'm doing a DIY installation here.

  • #2
    Originally posted by crashintoty View Post
    ..............Being this is a small, no so serious project, what changes would I need to make to compensate the gradual shading this set of panels will get and still get some energy from them.
    ......
    As long as your batteries are being charged this is a good science project. I wouldn't change anything. Maybe during the summer the sun will get higher in the sky and the shading will not matter. Twenty years ago I did one like that to power some landscape lights and learned a lot. I retrofitted most of the landscape lights to LEDs which was expensive back then. Long term when you get the grid tie system on your home you could add micro inverters to these panels and get some benefit from your investment in panels. By then your battery will probably have died anyway. Good luck and keep us informed.
    Last edited by Ampster; 02-24-2020, 04:15 PM.
    9 kW solar. Driving EVs since 2012

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    • #3
      Originally posted by Ampster View Post

      As long as your batteries are being charged this is a good science project. I wouldn't change anything. Maybe during the summer the sun will get higher in the sky and the shading will not matter. Twenty years ago I did one like that to power some landscape lights and learned a lot. I retrofitted most of the landscape lights to LEDs which was expensive back then. Long term when you get the grid tie system on your home you could add micro inverters to these panels and get some benefit from your investment in panels. By then your battery will probably have died anyway. Good luck and keep us informed.
      Really?!!! So, if the panel array gradually goes from 10% to 100% shaded over an hour or so, that really won't be a problem? The unshaded and then partially shaded panels won't be negatively affected? What if the panels are 300 watts, 56 volts each? In series instead of parallel?

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      • #4
        Generally, a shaded panel just shuts down.

        If it's in series with other panels, either it throttles ALL the panels way back, or the other panels "push through" utilizing the generally integral Bypass Diodes that are in nearly all panels and you merely loose the output of the 1 panel, till it's bypass diodes burn out.

        If the panels are in parallel, the shaded one still "goes to sleep" and the rest of the array is unaffected and bypass diodes are never activated.

        After 3pm, you are past the peak production hours anyway, and you won't loose much on a daily basis.
        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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        • #5
          Well, sounds like another case of me over thinking things. Thanks everyone!!

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          • #6
            Still plenty of thinking to do. You will have to pick a charge controller, a battery and figure out the loads that the system can power. Since I described it as a science project you probably want to measure the output of the panels over time to get some data. The data will be useful to size the other components.
            9 kW solar. Driving EVs since 2012

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            • #7
              Originally posted by Ampster View Post
              Still plenty of thinking to do. You will have to pick a charge controller, a battery and figure out the loads that the system can power. Since I described it as a science project you probably want to measure the output of the panels over time to get some data. The data will be useful to size the other components.
              Oh, that's already kind of planned out. A cheap charge controller supporting 100A, 200V input & a 12/24/36/48V battery system, 12 or 48V li-on battery (harvested 18650 cells) and cheap 8000W inverter. I don't have a real plan on what I want to power with this yet, maybe my home lab, since I'm going to be adding more servers soon. I figure when I go all in and put solar on the house itself, I'll get brand new solar panels and continue to use these cheap components temporarily before replacing them with better components (to cushion the new project's upfront costs).

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              • #8
                Originally posted by Mike90250 View Post
                After 3pm, you are past the peak production hours anyway, and you won't loose much on a daily basis.
                That was my first thought. Not much energy is harvested after 3 PM unless you have dual-tracking or fixed west facing panels and even then not that much extra. No problem for such a small "tinker" project like he plans to build.

                Dave W. Gilbert AZ
                6.63kW grid-tie owner

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                • #9
                  Originally posted by crashintoty View Post

                  ..........12 or 48V li-on battery (harvested 18650 cells) and cheap 8000W inverter.
                  You didn't mention a Battery Magement System. What are your plans for that?
                  9 kW solar. Driving EVs since 2012

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                  • #10
                    OP: Out of curiosity, what's your latitude and how sunny is it where you live ? Annual temp. change, winter to summer ? All that will have some affect on how PV/storage acts.

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                    • #11
                      Originally posted by Ampster View Post

                      You didn't mention a Battery Magement System. What are your plans for that?
                      I haven't found a cheap option, so I think I'm going to have to put up the $1000+ for Batrium BMS. Especially since I'm learning towards 48v battery system (14s or 16s for LiFePO4 if I get lazy and don't want to do the work to build the li-on battery).

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                      • #12
                        Originally posted by J.P.M. View Post
                        OP: Out of curiosity, what's your latitude and how sunny is it where you live ? Annual temp. change, winter to summer ? All that will have some affect on how PV/storage acts.
                        47.6600° N. Seattle, Washington. High 70's, low 80's in the summer; low 40's, high 30's in the winter.

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                        • #13

                          Originally posted by crashintoty View Post

                          I haven't found a cheap option, so I think I'm going to have to put up the $1000+ for Batrium BMS. Especially since I'm learning towards 48v battery system (14s or 16s for LiFePO4 if I get lazy and don't want to do the work to build the li-on battery).
                          I think you are wise to start with 48 volts. I use an Orion Jr which is around $600 and will do up to 16 cells. What I really like about it is the option to add the remote Orion Connect which allows me to remotely see battery voltage, current, temperature and individual cell voltages. The charts are great for looking at hourly, daily, weekly and custom date trends. That has given me insight into the vampire draw of my hybrid inverter and other trends not easily seen on the inverter screens. It is programmable so you can set voltages regardless of the chemistry. I did look at some less expensive options but based on the cost of Lithium batteries I did not want to risk losing my pack. i had a larger BMS for my EV conversion.
                          I am currently using some Nissan Leaf modules since I had them around from another project. Long term I am planning to upgrade to a LFP pack once I figure out my kWhr needs. There are some other forums for good information on Lithium batteries, The sticky here is also a good resource.
                          9 kW solar. Driving EVs since 2012

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                          • #14
                            Originally posted by crashintoty View Post

                            47.6600° N. Seattle, Washington. High 70's, low 80's in the summer; low 40's, high 30's in the winter.
                            And not an irradiance hot spot. Thank you.

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                            • #15
                              Originally posted by Ampster View Post


                              I think you are wise to start with 48 volts. I use an Orion Jr which is around $600 and will do up to 16 cells. What I really like about it is the option to add the remote Orion Connect which allows me to remotely see battery voltage, current, temperature and individual cell voltages. The charts are great for looking at hourly, daily, weekly and custom date trends. That has given me insight into the vampire draw of my hybrid inverter and other trends not easily seen on the inverter screens. It is programmable so you can set voltages regardless of the chemistry. I did look at some less expensive options but based on the cost of Lithium batteries I did not want to risk losing my pack. i had a larger BMS for my EV conversion.
                              I am currently using some Nissan Leaf modules since I had them around from another project. Long term I am planning to upgrade to a LFP pack once I figure out my kWhr needs. There are some other forums for good information on Lithium batteries, The sticky here is also a good resource.
                              Nice, that's much more budget friendly! Should I go with the CAN enabled version if I want the programmable stuff or is the CAN version meant for EV vehicles?

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