Trying to design an RV system

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  • halfwrighthalfwright Registered Users Posts: 15
    Re: Readings compared to the specs

    I mounted the panels with the Z mounts available here, so they do have air circulation underneath. I can't check the panels individually since I have them all wired in and mounted with butterfly screws. My biggest worry was that I might have wired one panel reversed, but since I am fairly close to what is expected, I don't think I did. I am planning on using a 30 amp fuse in this circuit. From the readings, will that be OK?
  • BB.BB. Super Moderators, Administrators Posts: 32,006 admin
    Re: Readings compared to the specs

    Actually, based on your Isc readings, it is possible that you have one panel that is not outputting current. If you can get to the individual panel wiring, I would suggest getting a DC Current Clamp Meter (~$60 for this model--good enough and includes the rest of the normal DMM type functions). Then you can directly measure the current without having to disconnect anything.

    If you have 4 panels in series, each panel is supposed to have a series protection fuse (probably around 15 amps or so for these) to prevent a short in one panel/wiring from being over driven by the other three panels.

    Fuses/Breakers/wiring should be rated for at least 1.25x the maximum continuous current you would expect. For the solar panel side:

    4*Isc*1.25 rounding up to the next standard fuse/breaker/wiring.

    Solar panels don't really output "excessive current" into a dead short the way a battery does--So additional fuses/breakers are usually there to make it easy to disconnect power from the solar input to your charge controller (The series protection fuse/breaker in paralleled solar panels are there and needed if you have 3 or more solar panel strings connected in parallel for most panels).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Trying to design an RV system

    a few points here.

    "but I finally got my 4 140 watt panels (wired in Series)"

    i don't think you can get higher than the isc rating of a single panel if they are in fact wired for series. a series wired array will add the voltages of each pv together while keeping the current the same as a single pv would be. you are describing a parallel array when the voltage is held the same and currents add. also note that the efficiencies for this may put it closer to 77% of the rated current and if the angle on the pvs are off the optimal then it gets worse on output current. of course if the sun itself is not shining down to you with its full potential at the time power suffers again.

    another point is that most multimeters can't take current readings that high. the test leads themselves won't take high currents either and will impose a v drop and a loss of overall power and current.
  • halfwrighthalfwright Registered Users Posts: 15
    Re: Readings compared to the specs

    I have finally finished installing erverything and doing some preliminary tests. The system will run the microwave at 141 12 volt amps. The system goes to float quickly and has past all my expectations. So far, the only problem has been the refrigerator and I am not sure that is the system or the "fridge. I need to try it with shore power.

    Thanks for all the help and advice I have recieved on this forum. It would have been much harder, if not impossible to have done it without the help.
  • BB.BB. Super Moderators, Administrators Posts: 32,006 admin
    Re: Readings compared to the specs

    Looks nice... My one suggestion--Add a fuse to your battery terminals. Some thing like these from Bluesea (one or dual fuses) would be nice:

    Attachment not found.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • DavidOHDavidOH Solar Expert Posts: 109 ✭✭✭
    Re: Readings compared to the specs

    Excellent Thread guys.
    This project is VERY similar to mine. ( http://forum.solar-electric.com/showthread.php?10461-My-Solar-Project )


    You might want a compromise on a PC. See my Low Power PC thread: http://forum.solar-electric.com/showthread.php?10467-Low-Power-PC
    This is a PC built to run using MUCH less power than a normal desktop. I have since built one using a newer Atom (525) chip. ( 1.8ghz DUEL Core! )
    Power consumption is 31 watts. Computer AND an 21" monitor! About what a laptop would use. It is not a powerful PC, but will do about anything I need.
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