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I have (x3) 150W panels, and need 1600Wh a day. Suggestions for battery banks?

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  • #91
    Originally posted by Sunking View Post
    There is no way you are going to learn a thing on You Tube or read in a book to learn what you need to know and how to do it. Those electricians and engineers coming out of school are GOFERS for the next 5 years learning how to not kill someone before they are trusted to work on their own.
    Yes, I understand that it's probably best left to the professionals, and by no means do I charge my safety to anyone besides myself. But there are also risks associated with just paying someone to worry about making something safe for you.

    And books are written by teachers, usually, with information more clearly organized than they are in lectures. There's no substitute for hands on experience, but I don't have that luxury at the moment.

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    • #92
      Safety precautions I plan to employ:

      I will be wearing rubber gloves rated to withstand 500 volts during the entire process.

      I will clear a clean space in a plastic or rubber container, and place place the batteries inside. I will not touch the terminals or allow anything else to. I will plug the battery bank together in series first, before putting it into parallel, using correct size wires that are rated to withstand to total possible combined current of all the batteries.

      The cables will be cut cleanly ahead of time, and crimped 100% to length of the lugs, with insulated heat shrink wrap around them.

      I will connect the batteries in series first, from positive to negative, because the positive is not grounded to the chassis, and if I screwed on the second battery lug to the grounded and completed the circuit, the neutral negative terminal post, (which is grounded) wouldn't potentially view me as a path to negative/neutral via ground. I will be stand on a rubber mat /and or wear thick rubber soled shoes (as well as the aforementioned rubber gloves) whenever I make contact with the exposed end of any hot cable or terminal.

      But if I screwed in the positive second, the circuit would be complete, electricity starts flowing, and some current could potentially use me as a path back to neutral/ground. Since the resistance of dry skin is between 1,000 and 10,000 Ohms, and since electricity flows in inverse relation to a paths resistance, (and copper wire is a much more conductive path) it's unlikely that it would travel through me, but it's obviously better to be safe than sorry.

      After the batteries are wired to each other, I will set up the charge controller, wiring it through an electrically insulated PVC pipe. It will be as close as possible to the battery bank, while still being outside the battery container. I will refer to the manual to find the order to connect the wires between charge controller and battery bank in the user manual. Failing this, I'll call Midnite Solar and ask.

      Then, I will install the panels, and connect them in series first, using the MC4 connections that they come with. I'll wire them to the charge controller in the same order that Midnite Solar recommended for the connection of the charge controller.

      After this, I'll give the batteries a full charge before I install the Inverter.

      I'll install the cable lugs to the inverter's positive terminal.
      I'll install the cable lug to the inverter's negative terminal.
      Put the fuse block down
      Install the positive cable from the inverter on top of it. Screw in MRB Fuse.
      Install the negative cable from the inverter on top of it. Screw in MRB Fuse.
      Figure out whether to ground to chassis either first, or last, as per manufacturer's suggestion.

      Everything is sealed, contained, insulated. Any outside damage happens to the system, (my RV flips or something) and I will contact the fire department or professional electrician (depending on severity) to assess the damage and repair it.

      So? Have I electrocuted myself in this scenario?

      Comment


      • #93
        Originally posted by Fractalcathedral View Post
        Safety precautions I plan to employ:

        I will be wearing rubber gloves rated to withstand 500 volts during the entire process.
        Why?

        12 or 24 volts will not shock you. The danger with 12, 24, and 48 volt batteries is arc flash. Without a protector glove over the rubber gloves, an arc flash will just melt the rubber glove to your skin for the doctors to peel off with your skin at the hospital. Professionals use insulated tools when working with batteries and safety goggles or face shields to keep acid out of their eyes.
        MSEE, PE

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        • #94
          Originally posted by Sunking View Post
          Why?

          12 or 24 volts will not shock you. The danger with 12, 24, and 48 volt batteries is arc flash. Without a protector glove over the rubber gloves, an arc flash will just melt the rubber glove to your skin for the doctors to peel off with your skin at the hospital. Professionals use insulated tools when working with batteries and safety goggles or face shields to keep acid out of their eyes.
          I've seen that although its rare, it's possible to become shocked or killed from 12 or 24v. I'll look into protector gloves. I'd rather have too much protection than not enough.

          I ordered the Midnite Classic 150, which has Arc Fault protection. How else would arc fault would relate to what I was doing, or how it could happen in my system without being related to lightning or a potential surge of fault power coming up from the grid?

          Would you put 15A fuses in between the modules? Is it potentially dangerous, optional, uneccessary, or recommended (per safety or code) to ground the modules to the chassis as well?

          Comment


          • #95
            Originally posted by Fractalcathedral View Post
            I ordered the Midnite Classic 150, which has Arc Fault protection. How else would arc fault would relate to what I was doing, or how it could happen in my system without being related to lightning or a potential surge of fault power coming up from the grid?

            Would you put 15A fuses in between the modules? Is it potentially dangerous, optional, unnecessary, or recommended (per safety or code) to ground the modules to the chassis as well?
            I am really growing tired of this. Arc Fault protectors do not protect you from arc flash. There is nothing that can protect you from Arc Flash other than knowing what you are doing and wearing protective gear.

            Try this and it will totally make you understand what an arc flash is. Take one of your batteries. get it charged up. Take a 2 foot piece of #6 AWG wire. Connect one end of the wire to positive terminal of the battery, then connect the other end to the negative terminal and see what happens. I promise you will not be electrocuted in any way. You just will not have any skin on your hands, torso, or face and be blind. You may die in the hospital while being treated for 3rd degree burns. The #6 AWG wire will vaporize and explode in your hands, and the battery may explode as will spewing boiling hot acid everywhere. But you will NOT BE ELECTROCUTED.

            The safe way is to understand what you are doing. First run all you wiring and get it terminated to everything except the battery post and solar panels. Make sure all fuses are pulled out and disconnect switches are open. When that is done connect all the Positive cable to the battery first making sure nothing is connected to the negative terminal.

            Once all the positive wiring is terminated to the battery make sure all fuses and switches are in the OFF or Disconnected state. Once that is done it is time to make the system HOT and connect all the wiring to the negative term post.

            Last connect the panels.

            Now you are ready to start turning things on one at a time. First is to put in the fuses between battery and CC. The CC should come to life, and if there is sun light the batteries should start charging.

            Once you are satisfied that the panels are charging the batteries, it is time to put in the fuses between the battery and load devices like the Inverter. Once that is done turn on the Inverter and check for proper operation. Follow up putting in any other fuses for other load devices and check for proper operation.

            Point here is once you connect the battery term post to the frame of the vehicle, the system is HOT because you grounded it. You safety guard is the fuses and and disconnect switches. As long as the fuses are out, and switches open the wiring is not hot, but the battery positive term post is HOT the second you bond the negative terminal to the frame. Keep in Mind your CC and Inverter has internal bonds from their negative terminal to the chassis. So as soon as you connect th enegative polarity up to one of those terminal, and it is also connected to the battery negative temp post the system is HOT.
            MSEE, PE

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            • #96
              Great, thanks.

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              • #97
                Originally posted by Sunking View Post
                Try this and it will totally make you understand what an arc flash is. Take one of your batteries. get it charged up. Take a 2 foot piece of #6 AWG wire. Connect one end of the wire to positive terminal of the battery, then connect the other end to the negative terminal and see what happens. I promise you will not be electrocuted in any way. You just will not have any skin on your hands, torso, or face and be blind. You may die in the hospital while being treated for 3rd degree burns. The #6 AWG wire will vaporize and explode in your hands, and the battery may explode as will spewing boiling hot acid everywhere. But you will NOT BE ELECTROCUTED.
                This sounds awesome.

                Comment


                • #98
                  Originally posted by mschulz View Post
                  This sounds awesome.
                  I know a bit harsh, lost my patience and I apologize for that. What I keep driving at and it is not sinking in is low voltage systems under 50 volts are not shock hazards and cannot drive enough current through the human body to do any real harm except in extraordinary circumstances.

                  The real danger is the batteries, and the amount of current they can deliver under fault conditions aka short circuit like connecting a 6 AWG wire from positive to negative terminal. Your average automotive starting battery has a CA rating on the order of 600 to 800 amps. What that means is the battery at 32 degrees can deliver 600 to 800 amps at 7.2 volts for 30 seconds. Well that is roughly 5500 watts of energy. Imagine hot and how fast that can make a wrench in your hands if it slips while tightening a connector on one post and makes contact with the opposite post. You do not get electrocuted, you get burned and burned badly.
                  MSEE, PE

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                  • #99
                    An apology from the Sunking? You owe no one an apology because your info is not only straight to the point but you are always helping us rookies from making a big mistake, whether that's what we want to hear or not, but you were showing a bit of your soft side. Don't make that a habit.

                    Comment


                    • Yeah Sunking, no apology needed. My "Great, thanks" probably came out as facetious but it wasn't meant to be. I just had alot of important questions answered, a few concepts reiterated/solidified, and needed a couple days to decompress and let everything sink in.

                      This entire thread has been enourmously instructive, thanks to everyone. Even the multiple calls to "Go learn the fundamentals" was helpful. I think I've got at least a basic understanding of lightning, induction, conduction, Coulomb's Law, the many variations of Ohm's Law, Resistance/Resistivity of certain materials, How to calculate wire size, and Joule's Law. I also saw a hilarious video of a seminar for firemen where they fry hot dogs and puppets to demonstrate arc flashes on actual live wires, so there's that. (Learning is fun).

                      I still have a few questions to try and clear up.

                      1. Grounding of PV module frame to chassis: Uneccessary, optional, or potentially dangerous?

                      2. Go Power! Recommends Class T Fuses for the inverter. Are there any inherent advantages of Class T over the Blue Sea 2151 Battery Fuse Block? It seems like the closeness to the battery would be an advantage in stopping fault current. I can't tell whether Go Power! is just trying to sell me on their kit.

                      3. (More theoretical): If you've got a charge controller, a battery bank, and an inverter all tied together on a positive bus bar, and then all tied together on a negative bus bar, how does the correct amount of current flow where it should?

                      Comment


                      • Originally posted by Fractalcathedral View Post

                        I have a couple questions remaining.

                        1. Grounding of PV module frame to chassis: Uneccessary, optional, or potentially dangerous?
                        Optional however most likely just the mounting hardware is going to bond the panels to the body unless you insulate them.

                        Originally posted by Fractalcathedral View Post
                        2. As for stacking 2 of those Blue Seas 2151 Bus Bars with MRB Fuses on the Positive Battery Term Post, they've got a combined 300A Rating.
                        So what is the question? All the 300 amp limit means is that is the maximum current the battery fuse blocks can safely handle. Stay under 300 amps and life goes on normally. Exceed 300 amps and you are in for a bad hair day. Just like a speed limit, stay at or below posted speed limit and all is fine.

                        Fuses and Breakers minimum size is determined by the wire size and load current. Fuses only purpose in life is to protect the wiring. For example if you have a 20 amp fuse the minimum size wire you can use is #12 AWG. However there is no problem using 1/0 with a 20 amp fuse. Wire size is based on the maximum LOAD current likely to be imposed on it and the amount of voltage drop you can tolerate.

                        So in your example if 42 amps is the maximum load current x 1.25 = 53 amps. So now you are looking for a 60 amp fuse or breaker. A 60 amp fuse must have at least a #6 AWG. If 42 amps of current causes to much voltage drop for the distance you need to run that 6 AWg then use a larger wire. Fuse does not change.


                        Originally posted by Fractalcathedral View Post
                        3. (More theoretical): If you've got a charge controller, a battery bank, and an inverter all tied together on a positive bus bar, and then all tied together on a negative bus bar, how does the correct amount of current flow where it should?
                        It goes to where it is required to go.

                        For example the batteries are fully charge, noon bright sun and you are demanding say 10 amps. It all comes from the panels because it is at the higher energy state. If the load demands more than the panels can supply, the the batteries much up the shortage. Current always flows from the higher energy state to the lower energy state (positive to negative). Think of it like a Tug-of-War on a rope with people pulling. Which way is the rope going?

                        Or water flow. Which way does water flow? From high point to lower point until it finds equilibrium.

                        EDIT NOTE:

                        My advice is this. Determine what the largest wire you will be using. Most likely the wire between the battery and inverter. Use that wire for everything. Only exception is possibly between panels a CC due to the raceway limitation might be too tight to say pull #6 AWG through. Just use as largest as you can. There is no problem using larger than required. You get real problems using under sized wire like safety and performance issues.
                        MSEE, PE

                        Comment


                        • Originally posted by Sunking View Post
                          So what is the question?
                          I edited it out because I found my answer after asking it. Thanks though, that all corroborates to what I found.

                          Originally posted by Sunking View Post
                          Or water flow. Which way does water flow? From high point to lower point until it finds equilibrium.
                          Again I must iterate: Strange world we live in that features such elegantly analogous principles. (The way that rivers bifurcate in similar patterns to trees, or whatever. There are a million examples of this in nature.)

                          Originally posted by Sunking View Post
                          Just use as largest as you can. There is no problem using larger than required. You get real problems using under sized wire like safety and performance issues.
                          Awesome. Good to know.

                          I had replaced my second question about fuses with this, and I'll just paste it here because I'm curious to hear your thoughts on it:

                          Go Power! Recommends Class T Fuses for the inverter. Are there any inherent advantages of Class T over the Blue Sea 2151 Battery Fuse Block? It seems like the closeness to the battery would be an advantage in stopping fault current. I can't tell whether Go Power! is just trying to sell me on their kit.

                          Comment


                          • Here's the final wiring diagram (perhaps) for anyone whose interested. Suggestions are always appreciated.

                            Wiring Diagram #4 (small).jpg

                            Comment


                            • Well, progress! After a ridiculous amount of trips to Lowes I got everything mounted on the roof and sealed, which when it rained, became quite an ordeal, (a combination of Dicor and Duct Seal worked for me). The solar wires run to a PVC fitting on the ceiling, through the ceiling, and everything is thoroughly covered by Electrical PVC and Flex Tube (Reminds me of playing with Legos). The batteries are sitting secure in a pretty heavy duty plastic chest by the wheel well.

                              I ran all 3 ground wires together in Flex Conduit, through the floor, a run of about 4 feet into a car battery terminal lug together, thoroughly enmeshed into the lug, which is mounted on a half-inch metal bolt with Internal/External tooth washers biting into chassis, and one of those nuts that has a washer inside of it. It's thoroughly firmly mounted shiny metal on shiny metal connection into the most structurally fundamental part of my bus, one of two giant beams that run from the back of the bus to the front.

                              Although I got a good connection, there appear to be rubber isolation mounts to isolate the engine vibration from the frame, so I'm still wondering whether it would be better to run a bare copper wire to the engine block, or whether that would be overkill at this point. And despite knowing basically where the engine block is, I don't know specifically where it would be best to actually terminate the wire.

                              Most of the grounding wires I've seen under the vehicle terminate on a part of the outer aluminum shell of the vehicle, but I was told by a mechanic that the wheelchair lift in the back of the bus had a large ground wire, and I could terminate ground wires on it anywhere, (but he was an idiot about a few things, so I take that with a grain of salt). I put together a game plan which is what I assume to be the correct method for wiring everything. I'm not very experienced with this but I think I understand the basic hazards. But I'd still like to fish out any remaining unknown-unknowns that could mess the whole thing up.

                              Getting all the PVC fittings into the Midnite Classic was a bit tricky, it's going to be a tight fit, but just short of waterproof. Although all the wires are ran, nothing is actually connected to anything at the moment, besides the ground wire to the Charge Controller. (I can undo this if its beneficial to hold off on the ground wire until later, it was just easier to do it than not). If any of this is unwise, please say so!

                              Step 1: Wait Until Night falls.

                              Step 2: Ensure all circuit breakers are in OFF and Disconnected state.

                              Step 3: Install series connections on batteries. A cable from Battery 1 (-) to to Battery 2 (+). Another cable from Battery 3 (-) to Battery 4 (+).

                              Step 4: Install parallel connections on batteries. Battery 1 (+) to Battery 3 (+). And then Battery 2 (-) to Battery 4 (-).

                              Step 5: Install Battery Temp Sensor from Charge Controller (first) to battery (second).

                              Step 6: Connect Charge Controller (+) to Battery (+)

                              Step 7: Connect Charge Controller (-) to Battery (-)

                              Step 8: Connect all 4 panels into 72v series.

                              Step 9: Connect PV (+) to Charge Controller (+)

                              Step 10: Connect PV (-) to Charge Controller (-)

                              Step 11: Set up Midnite Classic 150. (or should I do this before I connect the panels to CC?)

                              Step 11: Connect Ground Wire to Battery (-) Terminal Post. (I actually don't really know when I should do this, but I am guessing the later the better, because then the frame is bonded to the Negative power source, and any accidental connection between Positive Battery Terminal and Vehicle Chassis will result in a short).

                              Step 12: Turn Circuit Breaker between CC and Batteries ON.

                              Step 13: Turn Circuit Breaker between PV and CC ON.

                              Step 14: Wait until batteries are charged.

                              Step 15: Hook up Inverter (+) to Battery (+)

                              Step 16: Hook up Inverter (-) to Battery (-)

                              Step 17: Hook up Ground Wire to Inverter (or should this come before (+) and (-) connections?)

                              Is that good? Or am I mixing the order up anywhere?

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