DIY Solar panel setup on a budget

Discussion in 'Hobby Engineering' started by Mathuisella, Oct 15, 2013.

  1. dakiller

    dakiller (Oscillating & Impeding)

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    There is nothing wrong with doing this. My parents got 5kW on their place doing this, the south roof is about 10 degrees pitched, and the panels are on brackets angling them back. It made them quite hidden from view doing this.
     
  2. Sunder

    Sunder Member

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    For me, I don't think DIY main house solar was ever going to be on the cards. My dad bought one solar panel and one big deep cycle battery and thought he could just connect it up for his off-grid holiday home. Needless to say, it boiled his battery dead. Anyway, with only a very minimal of research, I thought, okay, just buy an MPPT controller, get another battery, and we're all good. Over the next year, we killed a fair bit of kit, and my wife figured this is what DIY solar was like. Unreliable, lots of things die, etc.

    I think the shocking thing I read was that something like 1 in 10 professionally installed solar systems had potentially lethal installs, and 4 in 10 had a non-fatal flaw that could cause under performance or unrelated issues like roof leaks. Some dodgy operators out there.

    In NSW, I believe if the neighbour's tree comes into your airspace, you can trim it without permission (Still want to ask though). But if it's in their yard but casting shade on you, there's nothing you can do. I even remember a case about that, where the illegal trimmer tried to use a "nuisance" clause in the law to have the tree removed. But the legal bar for nuisance is much higher than the common language use. Most people call a nuisance in common language, "an annoyance that doesn't cause much harm". But the legal definition is "A legal nuisance involves a substantial, unreasonable and repeated or ongoing interference with the use or enjoyment of a neighbour's land (examples include smoke, smells, noise and overhanging trees)."

    Judge disagreed that it was either substantial or unreasonable, given the other land owner was losing maybe a dollar or two of energy generation a day.
     
  3. Recharge

    Recharge Member

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  4. Sunder

    Sunder Member

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    Wonder if there's a 2 string version. I'm using bus bars, which is fine, but this is neater. Gonna hunt on that guy's Aliexpress store.
     
  5. Recharge

    Recharge Member

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    from 2 to four. they have quite the range. just watch the shipping costs, it's not much, just be aware.

    I've seen five on other stores though.
     
    Last edited: Jul 5, 2019
  6. vk2fro

    vk2fro Member

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    Are you going to wire 4 strings in parallel there Recharge??
     
  7. Recharge

    Recharge Member

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    4 panels, not strings. though I could do strings, I have 10 panels from my upgrade to play with.
    currently for the salt cell in the pool. electrolysis likes the amps.
     
  8. vk2fro

    vk2fro Member

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    thats what I plan to do with mine - 4 strings of 2 panels each in parallel, gets me around 100V at 20A into the charge controller.
     
  9. Recharge

    Recharge Member

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    thats gonna be a nice chunk of power! play carefully :shock:
     
  10. vk2fro

    vk2fro Member

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    My plan is to get all the wiring from the controller to the splitters and + / - of the panels done first, then join the series sets. Those final connections will be done at dusk, so lest likely to be zapped. When I join them I'll be wearing linesmen's gloves just in case. :)
     
  11. Recharge

    Recharge Member

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    I need to save up and buy a roll of 4mm cable (perhaps 6mm for shits and giggles)
    100m should cover me for, well, forever or so.
     
  12. vk2fro

    vk2fro Member

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    Yes I want some proper 6mm solar cable myself. I should only need 20m of the stuff though. Just need to get down from the roof to the charge controller, and some links between the junctions and the further panels.
     
  13. Recharge

    Recharge Member

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    buy 50m to be sure and gumtree the rest
     
  14. Sunder

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    So, long story short, I've had to downgrade my inverter to non-battery, because apparently it only takes a Modbus capable battery. Those are $9k for the same capacity we could probably build here for less than half the price. Cheaper if you use wrecked Leaf packs.

    Anyone ever thought about building a "Solar panel simulator"?

    E.g. A battery plugged into the solar panel inputs of the inverter.

    It has a NO voltage sensitive relay to keep it off the circuit until the solar panels drop below a certain amount

    A diode to prevent back current on the solar system (Should be one on each panel anyway, but never hurts)

    A second NC voltage sensitive relay inverted controlling a 240vac -> <Battery Voltage> vdc charger, so when it detects there's power being generated by the solar panels, it charges the battery.

    Am I completely off my chops, or does this have merit?
     
  15. Recharge

    Recharge Member

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    yep, the same reason I didn't go that route. propriety bullshit.

    no idea on the idea, brain currently offline with brain fog
     
  16. Sunder

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    Fair enough. I'm not going to put one in for at least a few years until my wife forgets the cost of this install anyway :p
     
  17. aXis

    aXis Member

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    Why have the second AC - DC charger?

    Just connect the "solar panel simulator" in parallel with the other solar panels, using a bidirectional DC-DC converter. When the panel output is high, pump charge from the solar into the batteries. When the panel outout is low, pump charge from the battery to the solar (inverter input). The hardest part is the difference in voltages, panels strings are up to 500V so it would be easier to have a higher voltage battery pack.

    The underlying bidirectional DC-DC technology is pretty simple (one inductor and two mosfet switches), but controlling it accurately is tricky.
     
    Last edited: Jul 10, 2019
  18. Recharge

    Recharge Member

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    and tricky usually means expensive.
     
  19. Sunder

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    Yeah, the trickiness. I haven't had time to think this one through properly, as I am meant to be at work, but thought I'd shoot off a message to collect thoughts before I reviewed them tonight.

    Really, all I want to do is have enough battery power between Sundown and 10pm (off peak). If I can do a bit of cooking and keep the lights on from 5pm to 10pm, 15c/kwh power doesn't phase me. 54c/kwh on the other hand... In summer, there will probably be enough sun to keep the air con going (1800w if all 3 are going) until about 7pm anyway. And in winter, heating is done by gas.
     
  20. aXis

    aXis Member

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    The first diagram on this page here shows the basic topology. You just have to switch those switches precisely, and also make sure you avoid shoot through. Oh, and manage 48V+ high side drive voltages and 500V blocking voltages. Easy! :shock:
     
    Last edited: Jul 10, 2019

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