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  • Bus Conversion Solar Addition

    Hello All, first post here. My and Wife live in a retired Ski Shuttle that we converted ourselves into a tiny home. We’ve been living in it for about two years. We recently bought some land in Pagosa Springs, CO and will be moving there soon. When we first built the bus we put in a complete electrical system that has served us well. I set it up in order to have some solar capacity but we’ve been plugged into shore power pretty much the entire time we’ve been living in the bus minus the occasional cross country road trip. Here’s the setup:




    -4 Vmax SLR155 AGM 12v Deep Cycle 155ah (620ah)

    -Renogy 4 100w panels (Mounted in Series-Parallel)

    - Rover 40a MPPT

    - AIMS Pure Sin Inverter/Charger 2000w with 6000w surge 50ft 10AWG Solar Cable

    - MC4 Male/Female Connectors TriMetric TM-2030 Battery Monitor
    12v distribution center




    Loads: 2 12v Led lighting strips (primary lighting
    12v Water Pump
    Suburban Propane heater electric ignition 12v
    Magic Chef 4.3 cuft fridge (main consumer, on startup it will surge about 10-12amps, including inverter, and when maintaining it will run 2amps including inverter)
    Aims Inverter/Charger
    Occasional Laptop and phone charging




    With this setup my battery bank (12v Parallel) will last rough 28 -32 hours to get to 50% ie using 310ah. Obviously my 400w array doesn’t do much to fully charge the battery bank. I received the panels from a friend for free so I can’t complain.




    Here’s where I need some help, with our soon to be move to Pagosa I would like to move to 100% solar. I have a backup 2000w gas generator to use in case of emergency. Ideally, I’d like to stay around $1k to beef up my setup. I’ve been thinking of either getting a new charge controller, 80a or up, or getting another charge controller and installing it in addition to the existing Renogy 40a MPPT. Is it a good idea to hook another CC up to the battery bank with my current Renogy MPPT? I’ve thought about going the 24v route but I don’t want to switch out all my lights, water pump, water heater, and inverter. As my setup sits now I’ve thought about adding 200w more to my 40a MPPT and then getting an additional 60a or 80a MPPT and putting somewhere between 600-800w worth of panels(Grid tied or 12v?). The property we have has great southern exposure on a hill and typical gets 6-8 hours of useable sun midwinter (gotta love the SW!). Any help on MPPT choice and how to setup my next array would be greatly appreciated!

  • #2
    So, first off, the aims inverter is quite large, and likely has an enormous idle consumption. That's not helping your battery life.
    400w of PV, might generate 30A for you on a great day, so plugging into an additional PV array would be great.
    As much wattage as you can afford, as your batteries should be happy with 60A of charging current.

    Sizing PV arrays, you can use expensive 12V 100w panels and a cheap charge controller, or cheap 250w panels and expensive MPPT Charge Controller. Above 300w, usually the higher voltage panels and MPPT are more efficient/cost effective.

    Adding charge controllers in parallel is not a problem. Having many 12v batteries in parallel is a problem, getting all the amps to be shared equally. The smartguage site has a good tutorial on properly wiring batteries, but even better is using lower voltage batteries in series. http://www.smartgauge.co.uk/batt_con.html
    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 for the reply Mike. The AIMS does have quite a large idle consumption. There is a power saver mode that seems to work alright where when it senses a load it kicks on. At least 60A seems like a pretty good goal to shoot after. At this point I'm more leaning towards mounting another MPPT in parallel with my current Rover 40A with the 400W array then replacing the Rover for a new system all together. Anyone out there used the Rover in parallel with another MPPT? Any MPPT recommendations for parallel charging? I definetly want at least 60A MPPT capacity.

      The 250W panels that you are talking about are grid tied panels correct? The reason that the MPPT is more expensive is that it has to handle a higher voltage with grid tied?

      Thanks for that link. I have my batteries setup in parallel with the load/charge on diagonal terminals of the bank as shown in the link as "Method 2". Seems to work well, in hindsight I wish I would've setup a series battery bank with 6v batteries but at the time I didn't understand a lot of the advantages/disadvantages of parallel vs series battery bank. At this point in the game it's too late for me to convert all my lights, appliances, and inverter to 12v.

      Thanks for all the help!

      Comment


      • #4
        Originally posted by samroon View Post
        .....

        The 250W panels that you are talking about are grid tied panels correct? The reason that the MPPT is more expensive is that it has to handle a higher voltage with grid tied?

        .......
        Generally, panels over 150 w are "Grid Tie" style, made for low current, high voltage. Same Watts, but can use 12ga wire instead of 8ga. The MPPT controllers are a lot smarter and complex, that's why the cost is higher. Looking at the midnight line, the 150V , 200V, 250V , 300v controllers, only few bucks difference between voltages, but the MPPT is where the $ cost is.
        I have one array running about 170V, and can use thin wire for the 200' run. If I used low voltage panels, I'd have to did a new trench and use larger conduit for much larger wire. Lots of cost in long runs of thick copper wire.

        GT panels are made by the billions, and cost / watt is pretty low, 12V 100w panels are nearly double the cost/watt
        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


        • #5
          Thanks for the help Mike. All of that makes good sense and I'm wanting to go with the GT Panels. I emailed renogy and this is what they said about using the Rover 40A in parallel:

          "Unfortunately, you cannot parallel two controllers together on the same battery bank unless it is the Rover 60a or Rover 100a and they are the same controller (60a with a 60a or 100a with a 100a). Any other controller we offer with a second controller on the battery bank will see the other controller as an outside source charge and limit the current to the batteries as it will not want to overcharge the batteries."

          Does anyone out there know if there is an MPPT out there that can be paralleled to the Rover 40A and be able to communicate with it properly? Thanks!

          Comment


          • #6
            This is wrong. Each set of panels needs its own controller. You connect the controller output to the Battery. As long as each array has it's own MPPT or PWM controller, several arrays can connect to a single battery bank. I have a Midnight and a Morningstar controller connected to my bank, works just fine.
            The only glitch is, getting both controllers set to the SAME voltage. Because of parts tolerance, even 2 controllers from the same company will not always match each other so you need to implement custom settings on one controller so it matches closely to the other one. Some controllers have a "Follow Me" mode to ameliorate this issue, but it's not required if you can match one's settings to the others.
            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


            • #7
              It’s true on two Rover 40a controllers, I didn’t see the fine print and now have two for sale. I went with a Midnite to handle my panels, can’t wait to use it.
              1.2 kWh solar 10.56 kWh battery @ 24v in a RV

              Comment

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