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  • Originally posted by Mike90250 View Post

    You are aware that fuses cannot be used to manually open a circuit . Breakers (esp the Midnight DC rated ones) can be used as switches for troubleshooting.

    Remember, touch safe fuse holders are only safe to open when the current flow is stopped, either blown fuse, or manual cut off somewhere.
    I tried to tell him. He wants to waste money for something he does not need or really wants if he knew the restrictions. He just added expensive eggs to his basket.

    MSEE, PE

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    • Actually the MidNite Baby box is much less expensive than posted above.
      Alt-E sells it for $37.XX https://www.amazon.com/MidNite-Solar.../dp/B007IAIW7S

      There is a misconception here about the requirement for overcurrent protection on PV systems. I will try to clear it up here.
      Overcurrent and disconnect is required down at the point where all other solar equipment disconnects are located. You only get 5 motions of the hand to shut everything off. That typically is not a problem, but you do need an overcurrent device and disconnect even for one string. The concept of not being required until you have three strings is meant for combiners. Here is the rationale. Take a solar panel that has a UL listing for a 15 amp overcurrent device. UL or ETL or TUV has tested and certified the design of that panel to not burn up with 15 amps of current flowing in the traces. Most panels have a short circuit rating of only 10 amps or so. You do not need a combiner for this as you are not combining. Now add a second one of those panels in parallel. You now have about 20 amps of current capability, so your disconnect/OCPD needs to be sized accordingly. (156% of short circuit current). You still do not need a combiner for this paralleled configuration. If one of the panels develops an internal short, the good panel is going to back feed it. The good panel can only produce 10 amps of current, but UL has determined that each of those panels is safe with up to 15 amps of current flowing, so you are still safe from causing a fire. Now let's add a third panel in parallel. If one of the panels develops a short, there will be two good panels backfeeding the bad one. The two good panels can put out a total of 20 amps. This exceeds the tested and certified rating of a single panel. This is now where you need a combiner with three breakers or fuses. In off-grid applications people always opt for breakers. I hope this clears up the mystery. Most professional installers do not even know the reasoning for this, but what I explained is the way it works.

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      • Originally posted by rgudgel View Post
        Actually the MidNite Baby box is much less expensive than posted above.
        Alt-E sells it for $37.XX https://www.amazon.com/MidNite-Solar.../dp/B007IAIW7S

        There is a misconception here about the requirement for overcurrent protection on PV systems..
        There is no misconception, it is even written into electrical codes clearly stated. Example in NEC 690.9, although does not apply to RV,s clearly states under Exceptions OCPD SHALL NOT BE REQUIRED where circuit conductors are sized in accordance with 690.8 where one of the following applies.

        No parallel external sources.
        Short circuit currents do not exceed the ampacity of the conductors or the maximum OCPD size specified by the panel manufacture.

        Could not be any more clearer than that. If the panel manufacture specifies a 15 amp OCPD and you panels adjusted ISC is 15 amps or less, no OCPD is required or needed. There is no possible way for the solar panel to generate enough current to even heat up a wire, let alone operated a fuse. Solar panels are limited current sources. They cannot possible generate more current than their ISC rating.

        Does not mean you cannot use them if you want, but there is no requirement or need for them.


        MSEE, PE

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        • WOW... That was a heck of a ride... I read every page, and I learned a lot!

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          • Got most stuff figured out and I'm down to buying my charge controller.

            I'm going to get a Epever tracer BN series MPPT, the question is how many amps 30 or 40?

            I can get the 30A unit for $165 and the 40A unit for $197, about $30 difference, not a lot SO it all comes down to amps and Watts supplied VS. what is best for the batteries?

            The 30A says it can produce 390w and the 40A and can produce 520w my only concern is the charge rate stressing the batteries. My 2 6V in series are rated at 214 amp hours SO... 40A is a C5.35 and the 30A is C7.13 charge rate.

            Since this is all powered by 2 -260w panels in series and the power supplied will vary depending on sun received not sure how much actual amps the batteries will receive and for how long?

            So is it better to get a 40A CC assuming the amount of amps and time supplied above 30A will be minimal based on sun received on panels OR is it better to get the 30A CC so it limits the charge rate to something more acceptable for the batteries as it will be supplied at 30A for a much greater time?

            These panels will be ran in a 5 hour winter sun area when in use.

            Thanks
            Last edited by Carv; 09-06-2017, 02:21 PM.

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            • Usually you tell the controller what type of battery and what the bank AH capacity is, then the controller charges it appropriately. So, if programmed correctly they'll both do the same thing correctly. I don't recall how you configured you panels nor your bank size/type, but the input voltage to the controller is important, as is the output Amps to the bank. Can you find the manual to the Controllers? I am pretty sure I would spend the extra 30 bucks for the future expansion ability.

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              • I've lost track of what you are doing, and there is a lot of noise in the thread. What specific batteries are you using? How will the panels be mounted (south facing, good tilt? flat mounted? shade/view of the horizon?).
                CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

                Comment


                • Originally posted by sensij View Post
                  I've lost track of what you are doing, and there is a lot of noise in the thread. What specific batteries are you using? How will the panels be mounted (south facing, good tilt? flat mounted? shade/view of the horizon?).
                  2 centennial 6V FLA wired in series for 12V -214AH rated.

                  Panels will be 2 -260w 60 cell, wired in series, flat mounted on trailer roof located in a 5 sun hour area no shade unless it's cloudy, which is rare, it's southern az desert, west of Yuma.


                  basically I'm asking how much of the day will the panels produce more that 390W?

                  Also I'm going to run battery tempature sensing on the controller and this is a once a month for 3 days use application, it won't be running 24/7.



                  Joe Ross, your talking about charging volts which I'm aware of, I'm talking about charging amps and what the batteries can handle VS. what the panels/CC will actually produce and for how long.
                  Last edited by Carv; 09-06-2017, 03:43 PM.

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                  • Originally posted by Carv View Post

                    2 centennial 6V FLA wired in series for 12V -214AH rated.

                    Panels will be 2 -260w 60 cell, wired in series, flat mounted on trailer roof located in a 5 sun hour area no shade unless it's cloudy, which is rare, it's southern az desert, west of Yuma.
                    I'd stick with the 30 A CC here.
                    CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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                    • Originally posted by sensij View Post

                      I'd stick with the 30 A CC here.

                      Any reasoning behind this?

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                      • Originally posted by Carv View Post


                        Any reasoning behind this?
                        I don't see the benefit here of pushing more than 30 A. AGM's would like it, some higher end FLA's would take it, but nothing in what you've written suggests you need to do that. Centennial recommends not pushing the charge rate too aggressively, probably for good reasons (less efficient charging, more heat build up, more water consumption, etc). 30 A is plenty.
                        CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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                        • Ok thanks. Sounds like 30A it is.

                          If I went to Trojan T105's would you recommend the 40A CC?

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                          • Originally posted by Carv View Post
                            Ok thanks. Sounds like 30A it is.

                            If I went to Trojan T105's would you recommend the 40A CC?
                            If you lived somewhere where weather is a bigger factor, and you *needed* that extra current to complete the charge, I think the 40 A (with the Trojans) could make more sense.
                            CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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                            • For those of you who've read this thread trying to learn something, here's the final product.

                              I still have to make a few small changes but it is a functional system.

                              And .....the cable porn
                              IMG_20170920_183349099.jpg


                              I did find a midnite baby box on ebay for $22 so I ditched the square D but in the end I wish I would have stayed with it. The baby box has DIN rails in it already but it's cheaply made and I can bend every bit of it by hand. With the modifications I made to it to accomidate the cord holds I wish I would have gone with the Square D and just modified it with DIN rails as it is a much stronger box.


                              On another note; I found out that on a ITC-1000 12V digital tempature controller, the 12V power source is seprate from the cool/heat relay on the controller so I was able to wire it in to run off 12V allowing the temp controller to run while the fridge and inverter are in sleep mode and when the relay connects (over/under set temp) it wakes the inverter out of sleep mode. I like this version of the controller the best because it has a power on/off button on the controller allowing me to turn it on and off as desired. This will greatly reduce the amount of watts I use to run the fridge to the point I'd bet I could run it for 5 days with out charging the batteries.
                              https://www.amazon.com/All-Purpose-F.../dp/B008KVGWT4


                              My first trip is in a week so Ill report back on how it works then.




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