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  • Checking my solar idea

    I am brand new to this and figure ill check with more informed.

    I have 5 renogy 255 watt panel, 40 amp renogy controller.

    I want to start by hooking up 4 of the 255 watt panels at 24 volt. They are 8.3 amp panels. I want to run these parallels into my c.c. I need to parallel them to keep volts down as the c.c. has enough amps. From the c.c. to 2 6v 215ah batteries. Ill get more as I can. From the batteries into a 2000w inverter.

    Doss this all seem reasonable? Ill add more batteries every month in 2 packs.


    As of now my bank will be 12 volt, but within two months I can create a 24 volt bank.

    I'm in sc and get roughly 5 hours of son.

    I need roughly 1200 watts a day

    Thanks to anyone who finds time to respond.

  • #2
    I wouldn't hook up more than three of those panels until you grow your battery. Over two panels in parallel need to be individually fused. You need to check the terminology on your loads. You will want to express that in Watt-Hours, not just Watts. Let me know if you have trouble with any of that.

    I assume your CC is a MPPT. If it is a PWM, it needs to be replaced or you need to bring your battery bank up to 24V before you put any panels to it.

    You won't be wanting to pull anything close to the full load on that inverter, but I'll let others amplify that - I have swore off inverter questions for a while.
    Last edited by AzRoute66; 09-10-2017, 01:24 AM.

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    • #3
      Th for the reply. I need to run a converted chest freezer. Roughly .6 kWh a day. Small light and tv tops for now.
      three panel and my mppt 40 amp into 2 6v 215 ah should suffice for a month? I appreciate the knowledge.

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      • #4
        I understand you don't want to speak of inverter. I have to ask though, would running it half load be cool?

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        • #5
          I'll try to answer that without answering it.

          Your battery: 12V x 215 Ah = 2580 Wh. To not exceed the 50% depth of discharge rule of thumb we'll say that is 2580 Wh / 2 = 1290 Wh available.

          Your panels: 3 x 255W x 5 sun hours = 3825 Wh. More than enough to charge your battery and power fridge under typical conditions.

          So, the fridge will take power during the day from the panels, and otherwise from the battery so let's assume 600Wh x .75 = 450 Wh from the battery.

          The leftover would be 1290 Wh - 450 Wh = 840Wh per evening for the TV and the lights.

          Note that these are ideal conditions, and you may have several cloudy days headed your way real soon thanks to Irma.

          I think you can see that the battery has a lot of room for growth. Make sure you add those batteries as soon as practical as mixing batteries always draws the bank down to the weakest link, and sometimes even worse. Put one of the newer pair in series with one of the older pair, don't parallel the new with the old. You should be able to see how this will make it difficult to keep adding batteries in pairs. Good luck.

          Again, this is a DC only analysis. The inverter element adds more inefficiency/considerations, none of which are going to improve anything I've laid out.
          Last edited by AzRoute66; 09-10-2017, 03:07 PM.

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          • #6
            Thanks a ton for taking the time.

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            • #7
              Originally posted by teknatronik View Post
              I am brand new to this and figure ill check with more informed.

              I have 5 renogy 255 watt panel, 40 amp renogy controller.

              I want to start by hooking up 4 of the 255 watt panels at 24 volt. They are 8.3 amp panels. I want to run these parallels into my c.c. I need to parallel them to keep volts down as the c.c. has enough amps. From the c.c. to 2 6v 215ah batteries. Ill get more as I can. From the batteries into a 2000w inverter.

              Doss this all seem reasonable? Ill add more batteries every month in 2 packs.


              As of now my bank will be 12 volt, but within two months I can create a 24 volt bank.

              I'm in sc and get roughly 5 hours of son.

              I need roughly 1200 watts a day

              Thanks to anyone who finds time to respond.
              your batteries are too small for your current controller- 40A are very close to C/5 charge current and that is usually too high for deep cycle FLA: http://www.trojanbattery.com/pdf/Tro...UsersGuide.pdf page 19 shows highest current at 10%-13% of its capacity C which would be 28A tops in your case. Hard to tell without knowing your exact battery model. Adding batteries to the bank over time is a bad idea- collect all your money and then buy batteries/cells all at once and commission them all at the same time.

              BTW 40A usually refers to the output current value of your CC, not how much current it can take from panels. You can connect 1000 A of panels to its input and nothing bad would happen- it will take as much as needed leaving the rest not utilized. What is critical on CC input is the max voltage it can sustain. Panels have this max voltage Voc in their data sheets usually specified for 25C STC. You need to correct it to the lowest temp you can have at your location (and some) using another Voc temp coefficient from the panel's datasheet and check if your CC will survive. If your CC input would sustain multiple panels in series when their Voc add up I'd recommend to do that vs parallel connection to reduce losses and simplify things.
              Last edited by max2k; 09-10-2017, 03:12 PM.

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              • #8
                Yes, I saw the C/5.3 the next morning as I was writing post #5, but think it will be fine for a month or so, but just for completeness could the OP tell us specifically what brand/model of battery he currently has, and what he intends to add?

                Also, is the charge controller the Renogy Commander or some other? Specifically I am wondering if there is a Max Charge Current setpoint we can use to tone things down just a tad until you get to 24V on the battery.

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                • #9
                  I have yet to buy batteries, but I was going with the Duracell 6v 215 ah for 99 at batteries plus.

                  The c.c. is a commander. Voc on panel is 37.4

                  I think the c.c. is rated 100 volts.
                  Last edited by teknatronik; 09-10-2017, 04:33 PM.

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                  • #10
                    Sorry, I read that first post to assume that the first pair of batteries was already locked in. I assume that is the Duracell SLIGC110 we are talking about. Although I can find no real spec sheet on it, what little I saw leads me to believe it will handle the C/5 charge just fine.

                    This is a SLI battery, at best a 'hybrid', hence the 'SLI' in their model number.

                    Since you are not yet committed to them, I suggest you read all of the sticky threads in the Batteries forum and perhaps select a slightly more robust solution. Should you stick with them, I would try very hard to go to 24V on your first pass.

                    Just curious, are the five solar panels and the charge controller something that you already have in hand or just items that you are considering?
                    Last edited by AzRoute66; 09-10-2017, 05:09 PM.

                    Comment


                    • #11
                      Originally posted by AzRoute66 View Post
                      Sorry, I read that first post to assume that the first pair of batteries was already locked in. I assume that is the Duracell SLIGC110 we are talking about. Although I can find no real spec sheet on it, what little I saw leads me to believe it will handle the C/5 charge just fine.

                      This is a SLI battery, at best a 'hybrid', hence the 'SLI' in their model number.

                      Since you are not yet committed to them, I suggest you read all of the sticky threads in the Batteries forum and perhaps select a slightly more robust solution. Should you stick with them, I would try very hard to go to 24V on your first pass.

                      Just curious, are the five solar panels and the charge controller something that you already have in hand or just items that you are considering?
                      well it says 'deep cycle' in the specs: https://www.batteriesplus.com/productdetails/sligc110
                      and if it is SLI indeed I'd strongly advise OP to look elsewhere. In any case it is not AGM and C/5 charging current will kill it probably within 1 year.

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                      • #12
                        From that same page you referenced:[LIST][*][B]Product Category:[/B] Golf & Scrubber[*][B]Product Sub Category:[/B] Starting Lighting And Ignition[/LIST]It said 'deep cycle power', kinda like i have 'tiger woods power' I think. 'Chocolaty taste' perhaps. Deep cycle power without all of the weight... etc.

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                        • #13
                          Originally posted by AzRoute66 View Post
                          From that same page you referenced:[LIST][*][B]Product Category:[/B] Golf & Scrubber[*][B]Product Sub Category:[/B] Starting Lighting And Ignition[/LIST]
                          It said 'deep cycle power', kinda like i have 'tiger woods power' I think. 'Chocolaty taste' perhaps. Deep cycle power without all of the weight... etc.
                          it is not AGM anyway and will be suffering at C/5 charging rates as it is about twice of the max it is designed to handle.

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                          • #14
                            Would you mind leading me a reasonably priced battery for the setup?

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                            • #15
                              In general, for cost you want to avoid shipping costs and that depends largely where you are and how far you are willing to drive. I live in a small community 13 miles from the Mexican border and I would start my battery shopping in Phoenix, 200 miles away - but would keep my eyes open for Tucson which is half the distance.

                              Perhaps more importantly would be how to identify a true deep cycle battery. Take a look at the specification sheets, or 'data sheets' for Trojan, Crown, and Rolls - the leaders in deep cycle. Notice how they all show a table of Ah capacity for multiple hour discharge, and Cycle Life vs Depth of Discharge and none of them show CCA or MCA? You can expect a true deep cycle battery from any manufacturer to follow suit whether AGM or FLA.

                              The good hybrids are a little harder to sort out, but for instance many of the Costco golf cart batteries are made by Interstate, and you can find the spec sheet for the Interstate branded version and go from there. Many of the marine hybrids are a decent choice and they will have good disclosure. I have a real issue with your Duracell choice not because they are a bad battery, but because I cannot seem to find any hard data on them. I can't deny that $100 is a great price, but I truly fear you will get what you pay for.

                              My hunting buddy is going for a four pack of AGM from Brand ___ as the next set for his camper. When I asked him how he selected those he was vague, but I got the distinct impression that it was mainly from review testimonials and a "10% off your first order and free shipping" offer.

                              I wish I could tell you to go to webpage X and order brand Y but I really can't. It is so time and geography dependent.

                              Our resident battery expert (@Sunking) would tell you in order to compare two similar batteries you really only need two pieces of information: the weight and the warranty, and that is more accurate than it sounds at first blush.

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