Need help with off-grid cargo trailer toyhauler project

nomad
nomad Registered Users Posts: 4
I recently purchased a 7x14 cargo trailer for use as a toyhauler/camping/shop/surveillance platform. My intent is to equip it with off grid capability wind/solar that can also be used to provide back-up power to my house in the event of an emergency. I have purchased 2 GS-250 Grape Solar panels, one morningstar MPPT 60 charge controller, 1 Magnum MS4024 PAE inverter/charger and one E-panel MNE 250-stm-240, and 1 Trimetric 2025 battery monitor. I am also awaiting delivery of 4 Trojan L16 Re batteries that I intend to wire as a 24 volt system. I already have a 8hp 4000w generator that I have converted to propane. My questions are:

1) What combiner box would enable me to grow this system to it's rated capacity?
2) What other ground fault interrupters do I need if any?
3) What am I missing?

Thanks

Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Need help with off-grid cargo trailer toyhauler project

    Welcome to the forum.

    First, forget about wind. On a trailer it is not going to work no matter how good a unit you buy because you really can't get it up a 50' pole where the 'good' air is.

    Second, it sounds as though you've gone and bought equipment without planning the whole thing out. This would start with determining how much power you need/want to get from the system. As it is the four L16's are going to be in the neighborhood of 320+ Amp hours @ 24 Volts, or a maximum of about 3.5 kW hours AC. Your two 250 Watt panels aren't going to do very well at recharging them, being capable of about 16 Amps max through the MPPT controller on a 24 Volt system. At best that will be 5% charge rate, and Trojan recommends 10% for those batteries. You will be running that generator a lot. Perhaps you had planned on that to power large equipment and thus want to take advantage of it while it's running, using the panels to reduce the charge requirements?

    The Morningstar MPPT 60 is definitely overkill at this point. But won't be if you add, say, four more panels.

    What combiner box you use depends on how much you plan to expand and how the panels are configured. For example the two panels you have are probably Vmp of around 30, meaning they should be wired in series for a 24 Volt system; no circuit protection or combiner box required. You could add two more of the same and get the charge rate up to 10% without adding fuses to the PV and have only two parallel connections which can also be done without a combiner box. How soon before you run out of roof to put panels on? :D

    You will not need/want any ground-fault circuitry; this is a trailer and is not connected to ground so there's not much point. Frankly that stuff causes more problems than it prevents anyway.

    What are you missing? Circuit protection for the charge controller and inverter, lots of wire of the correct size for current and Voltage handling, more miscellaneous bits of hardware that the need for inevitably comes to light at some critical point in the installation.
  • nomad
    nomad Registered Users Posts: 4
    Re: Need help with off-grid cargo trailer toyhauler project

    Thanks for your response. Could you expand on how would design the circuit protection for the charge controller and inverter? (I am waiting on two more grape panels)
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Need help with off-grid cargo trailer toyhauler project
    nomad wrote: »
    Thanks for your response. Could you expand on how would design the circuit protection for the charge controller and inverter? (I am waiting on two more grape panels)

    In this case you're simply looking at fuses or circuit breakers to prevent damage in the event of an over-current situation. Without an actual Earth ground available there is no other protection (such as stray Voltage from lightning) that can be provided.
  • Rybren
    Rybren Solar Expert Posts: 351 ✭✭
    Re: Need help with off-grid cargo trailer toyhauler project

    Your e-panel comes preinstalled with a breaker to protect the inverter (Make sure it's the correct size for your inverter). Pick up some Midnite DC breakers to use in the epanel for the PV and CC circuits.
  • nomad
    nomad Registered Users Posts: 4
    Re: Need help with off-grid cargo trailer toyhauler project

    Thanks. The e-panel is matched to the magnum inverter but I will check. I guess I need to find a diagram that shows how to size and install the breakers for the PV and charge controller.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Need help with off-grid cargo trailer toyhauler project
    nomad wrote: »
    Thanks. The e-panel is matched to the magnum inverter but I will check. I guess I need to find a diagram that shows how to size and install the breakers for the PV and charge controller.

    The basic install is not difficult:
    PV to charge controller: one fuse/breaker needed per string if more than two strings are in parallel, size according to panel specs.
    Charge controller to batteries: fuse/breaker needed rated for maximum expected current.
    Batteries to inverter: fuse/breaker needed rated for maximum expected current.

    Wire sizing is the same: it needs to be able to handle the maximum expected current in the circuit and be large enough to prevent any significant Voltage drop over the distance involved. The wiring should always be able to handle more current than the fuse/breaker on the circuit; you want the over-current protection to trip before the wire melts.

    Other than that the wiring become specific to the equipment used and the particular installation. There are thousands of variations possible with the basic theme.
  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: Need help with off-grid cargo trailer toyhauler project

    look on the midnite site for your model of epanel for a generic wiring diagram. there should also be one in the box, on the inside of the door...http://www.midnitesolar.com/doc_prod_list.php?menuItem=products&productCat_ID=1&productCatName=E-Panel%20-%20Outback
     
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