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  • 12 volt mobile equipment conversion to solar off-grid cabin...

    Hello all. I am new to this forum.

    Just a little about my background - I have a basic background in electricity and have a general knowledge of solar, how it works, and how it should be setup as a power source (probably just enough knowledge of both to be dangerous...).
    My company manages a mobile mammography/cancer screening unit for a local hospital. Due to an upgrade in x-ray equipment, they had to completely upgrade the power source on the truck with larger equipment. The equipment that was removed was given to me.
    I have -
    2 - Xantrex Freedom SW 815-3012 inverter/chargers (3 years old)
    2 - Xantrex TrueCharge2 Series 60amp battery chargers (3 years old)
    4 - 8275 series 12 volt GEL Batteries that have a 20 Hr. rate /225Ah (13 months old)
    I also have the remote panels that operate the devices.

    This equipment was configured in a "stacking" setup on the truck. I have spoken with the tech folks at Xantrex and they say that they will be happy to walk me through "unstacking" this equipment so it can be used independently.
    I have an off-grid cabin (no power currently) in southern KY that I would love to have power in.
    From what I've learned, 12 volt is better suited to mobile, RV and marine. Higher voltage setups are much preferred for things like cabins. I also understand that the voltage is not the dangerous part in what I'm considering. The danger is in the amperage...
    With that said, I considered selling these inverters and chargers and using the proceeds to by a higher voltage system. I gave eBay and Craigslist a shot but no luck. I got a couple of crazy low offers but nothing I wanted to consider.

    So here I am researching the viability of installing this 12 volt system in my cabin...

    Based on different online calculators I have experimented with, when we use the cabin, we need about 2200wh. That's probably a bit high but, I prefer to be conservative rather than disappointed.
    The place is small place and we only use it a couple of days at a time here and there throughout the year. To take advantage of the 12v, I can use a lot of RV type of accessories that are readily available (lighting, fans, etc.). Including an RV fridge that can run on propane, 12v, or 120v AC that I already have.
    By using a 1.5 "fudge factor", I come up with 3300whs.

    Here is where I think I'm going at this point. Maybe one of you good folks can redirect me if necessary...

    Inverter - Use the one of the 12 volt Xantrex 3012 inverters that I have to convert the DC for AC loads. 3000 watts is overkill I'm sure...

    Storage - My calculations tell me I need 1375Ahs for storage. I'm short here. As I indicated above, I have four 12v 225ah GEL batteries. I'm thinking of setting up two parallel 12v battery banks. That gives me 900Ahs total storage.
    When I'm at the cabin for several days in cloudy weather, I can always fire up a small generator and top everything off. Because we rarely use this place for more than 2 or 3 days at a time, as long as I don't deplete the batteries less than 50% (I'll probably try and keep it to 70%), the solar system can charge for days, if not weeks after we have left there...
    For AC charging - The Xantrex 3012 inverter has a built in battery charger. It senses AC power and will switch from inverter mode to charging mode automatically. It has 3 stage charging.

    For solar charging - The calculators tell me I need 917 watts of solar panels. I'm thinking of using three 300-watt panels wired in series. As I understand it, the solar panels come with cables (maybe 12 gauge) that have MC4 connectors. I also believe I can get MC4 extension cables (maybe 10 gauge) to run the 15' distance from the panels to the charge controller.
    The calculators also tell me I need a charge controller that can handle 75 amps. The Midnite Classic 150 SL MPPT is the direction I'm leaning. That looks to be a quality product with good reviews and gives me room for upgrading my system to 24v or 48v at some point down the road. This has a 96 amp rating so I can add on more solar panels if I want.

    Wire size - (THIS IS AN AREA IN WHICH I'M STRUGGLING) I don't have confidence in my level of comprehension of the higher amperage produced by using 12v to determine the appropriate fuse/breaker sizing and wire sizing.
    From the charge controller to the batteries will only be about 3 feet or less. I'm planning to mount the CC on the outside wall of the battery box. But, I don't know what the factors are to determine that wire size. Is it 96 amps? That is what the charge controller I'm considering is rated for. If so, use 4ga wire? I guess the terminals on the controller are big enough??
    The cables that are currently used to interconnect the batteries are big. I believe they are 2 gauge.
    From the inverter to a small AC load center, I'll run some 10ga wire and put that on a 30 amp breaker to feed AC loads to the cabin.

    I have attached an illustration/wiring diagram that illustrates what I'm thinking and highlights a couple of areas of concern I have... I am aware that all the devices need an earth ground that is completely independent from the DC negative and AC neutral. I did not show it on this illustration because it really cluttered things up.

    I also have concern with this place being remote and not used daily in the winter, there is no way to keep those batteries in a climate controlled environment. My understanding is that batteries in freezing weather is not good for them... They were in a non-climate-controlled compartment on the truck... Is that a serious concern? I know cold affects their performance, but my concern is more long-term damage.

    My guess is that there are a multitude things in the scenario above that are either incorrect or that even could be done differently. But this is my jumping off point to see where I need to go...

    To summarize what I'm considering (so you don't have to go back and reread everything...) -
    • 3 - 300-volt panels in series for 900watts.
    • A Midnite Classic 150 SL 96 amp MPPT (I need a CC to handle 75amps) --- what should the wire size be for a the 3' run from the CC to the battery bank? What sort of protection should this have? A breaker? Fuse?
    • 4 - 12v 225ah GEL batteries. Setup in two parallel 12v battery banks. 900Ahs of total storage. (calculated storage was 1375Ahs. I'm shy of what is calculated but I don't live here. So, I feel it's manageable).
    • 1 - Xantrex 3012 3000 watt inverter --- what sort of fuse protection should I have between batteries and the inverter?
    • Non-climate controlled battery environment. Is this a problem?
    Does this system seem viable?

    Thank you in advance to anyone that is taking their time to read through this and give input. It is much appreciated!!!

    Steve

    WIRING DIAGRAM.pdf

  • #2
    first, be sure you hook those batteries to a charger once a month, to keep them topped of, or they will be ruined.

    Welcome to the club, like a boat, it's a hole you pour $ into !

    Plan on the fridge being propane all the time, many of the 12v/ propane/ 120v fridges don't have a 12V compressor, they use 12v to run a heater instead of propane. That consumes a lot of power !

    Your 3000w inverter will consume a fair amount of power, just being turned on. You may be better off spending more $ for a smaller inverter (like the suresine 300) that is very efficient. Only power u[ the big inverter when you want to run the blender or microwave
    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

    Comment


    • #3
      Thanks Mike.
      The battery bank is currently hooked to one of the xantrex 60 amp chargers and they are in "float" of the 3 stage charging. Every seven days, that charger recycles the system somehow (don't know enough about it...).
      Good info about the fridge. I didn't know that was how it worked.
      I was going to use 12 volt for most of my accessories (lighting, fans, 12v water pump, etc.). Including the fridge... but based on what you said, that probably doesn't make sense.
      Your comment regarding the amount of power that the Xan 3012 inverter uses confirms my suspicion. This is a huge device. The thing weighs over 70lbs... It probably does use quite a bit of energy just to run itself. I had planned to turn it off when I wasn't using it. If we want to watch TV, make coffee or use AC appliances we would turn the inverter on.

      Honestly, this may be a poor plan to force myself to use something that was given to me. My goal was to use this monster 12v inverter because it was free and hopefully it would get me started in a solar setup... I could use my resources to buy solar panels, a charge controller and all the other components to get up and running. Then eventually buy a 24v or 48v inverter -switch up the battery config and be good to go.
      Selling these two 12v inverters and the two 60 amp chargers is probably the smartest thing to do. I just need to find someone with a big RV or a big boat that needs a high powered 12v system...

      Comment


      • #4
        [QUOTE=Ky Speedracer;n395034]Thanks Mike.


        Your comment regarding the amount of power that the Xan 3012 inverter uses confirms my suspicion. This is a huge device. The thing weighs over 70lbs... It probably does use quite a bit of energy just to run itself. I had planned to turn it off when I wasn't using it. If we want to watch TV, make coffee or use AC appliances we would turn the inverter on. [/QUOTE



        If this is the inverter you have you may not want to dump it just yet. These Xantrex inverter chargers are actually pretty sophisticated.
        From the manual "Search mode allows the inverter to selectively power only items that draw more than a certain amount of power, which can result in power savings. The Freedom SW has a no-load power draw of about 28 watts. Enabling search mode reduces this power draw to less than 8 watts. Search mode operates differently in single-unit and multi-unit installations."

        Here's the manual for the 12 volt 2000 and 3000 watt models.
        http://www.xantrex.com/documents/Inv...Rev-G)_ENG.pdf
        2.2kw Suntech mono, Classic 200, NEW Trace SW4024

        Comment


        • #5
          Originally posted by littleharbor View Post
          If this is the inverter you have you may not want to dump it just yet. These Xantrex inverter chargers are actually pretty sophisticated.
          From the manual "Search mode allows the inverter to selectively power only items that draw more than a certain amount of power, which can result in power savings. The Freedom SW has a no-load power draw of about 28 watts. Enabling search mode reduces this power draw to less than 8 watts.
          Thanks for the heads-up!
          To be honest, I read through that manual a while back. At that time, most of the info in it was difficult for me to comprehend. But, thanks to this forum and all the resources here, I spent almost an hour rereading it and I have a much better grasp on what all that info means.

          Comment


          • #6
            Originally posted by Ky Speedracer View Post

            Thanks for the heads-up!
            To be honest, I read through that manual a while back. At that time, most of the info in it was difficult for me to comprehend. But, thanks to this forum and all the resources here, I spent almost an hour rereading it and I have a much better grasp on what all that info means.
            You're welcome. Glad I caught which inverter you had.
            If and when you decide to change out inverters there's a market for these in used condition
            2.2kw Suntech mono, Classic 200, NEW Trace SW4024

            Comment


            • #7
              Originally posted by littleharbor View Post
              If and when you decide to change out inverters there's a market for these in used condition
              The equipment I have is a really nice setup. It's less than 3 years old.
              I have tried to sell the usual way (ebay, craigslist, etc.) with no success. Is there a forum here for used equipment?


              Comment


              • #8
                Those would have been my suggestions. Are you asking a realistic price?
                Not sure if you can offer it here. That would be a moderator question. Being located in a no grid, all solar area of Baja maybe my opinion is a bit skewed. That inverter would sell fast down there.
                2.2kw Suntech mono, Classic 200, NEW Trace SW4024

                Comment


                • #9
                  Originally posted by littleharbor View Post
                  Those would have been my suggestions. Are you asking a realistic price?
                  I was asking about 50 cents on the dollar. The inverters can be bought on Amazon for around $1600.00 each. I was asking $875.00 ea. The SCP panels are $175 each and I was just going to throw one of those in with each inverter. The chargers you can buy for about $550 each. I was asking $275. OR, I would take $2050.00 for all of it.

                  I didn't think that was to much, but maybe I'm wrong...

                  Comment


                  • #10
                    Sounds like fair pricing. I'd relist and hang in there for a while. BTW, Why are you wanting to sell the Midnite Solar CC's
                    2.2kw Suntech mono, Classic 200, NEW Trace SW4024

                    Comment


                    • #11
                      Originally posted by littleharbor View Post
                      BTW, Why are you wanting to sell the Midnite Solar CC's
                      I have 2 Xantrex TrueCharge 2 60amp battery chargers that were used on the truck setup. https://www.amazon.com/Xantrex-804-1.../dp/B006MYROFC That's what I was wanting to sell.
                      The Xantrex 3012 inverters have built in 150 amp battery chargers but they used these instead. Not sure why, but that was how it was setup originally.
                      The way I remember it, the inverters were stacked. One inverter (the master) was connected to 2 of the 12 volt batteries and had one of the chargers with it and then the slave was connected to the other two batteries and charger.
                      The entire system was setup kind of as a UPS for the x-ray equipment...

                      Comment


                      • #12
                        Where are you located?
                        2.2kw Suntech mono, Classic 200, NEW Trace SW4024

                        Comment


                        • #13
                          I'm located in Louisville KY.
                          i've looked for a way to PM on here but I haven't figured it out. My guess is, because I'm a new member to this forum, that feature is unavailable to me.
                          I do have the ability to skid these and ship by truck. if you're interested, I can provide an email address and provide more details.

                          Comment


                          • #14
                            Originally posted by Ky Speedracer View Post
                            I'm located in Louisville KY.
                            i've looked for a way to PM on here but I haven't figured it out. My guess is, because I'm a new member to this forum, that feature is unavailable to me.
                            I do have the ability to skid these and ship by truck. if you're interested, I can provide an email address and provide more details.
                            FYI, unless things have changed, the feature is unavailable to everyone. It does not exist on this forum

                            Comment


                            • #15
                              Gotcha...thanks!

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