DIY Solar panel setup on a budget

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

  1. rainwulf

    rainwulf Member

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    I understand your points HSV, but there are numerous design decisions i made in this usage case.

    I tested the relays and made sure that if one contact was welded shut, it would be impossible for the relay to physically move and close the other contact with the other supply. This was my number one concern to be honest. The active/neutral are switched together, or not at all if the contacts weld. I wanted to make sure that the load would at no time be "Straddling" the mains, especially if one side was at high side of the waveform, and the other side was at the low side, effectively putting 480 volts across the load. No current would flow as such as the solar side doesn't have a MEN link, but it would still be dangerous to touch. The other issue is that i would never want the solar and mains to touch, but the exclusive break before make of the relays makes that impossible. However... i have decided that the next version of this being inside a much bigger box would use 3 sets of relays per "output", with a 10ms activation delay between them all, with AC detection as well.

    I'm not interrupting the earth, its using two 20amp diodes back to back to provide .6 volts of dc isolation to provide some basic noise protection from the solar inverter to the house mains. It will also mean that an ELB/RCD on the solar side will function. Without joining earths, an ELB/RCD combo unit wont work on the solar side, and it also leaves any mains equipment on the output of this unit a functional earth to prevent electrocution should the active or neutral touch the chassis. Without joining earths, on solar power, faulty equipment wouldn't trigger any kind of protection. The back to back diodes and capacitors provide a "earth" level for the entire solar side of the system, while also providing noise isolation from traditionally noisy solar charger and pure sine wave inverter equipment. In retrospect, the X2 caps probably arent doing anything useful.

    The inductance of the pigtails have zero effect at 50hz, and at higher frequencies would actually help limit high frequency noise, especially from the inverter. I have left them there mainly because the AC connections inside the power sockets aren't fixed, and as leads are pushed in and removed they actually move around a little. Using pigtails gives the copper some give so that it doesn't work harden and break off.

    The next version of this would also have 10 amp slow blow fuses integrated into it, at the moment im using the 10 amp circuit breakers in power boards for high current protection, which is not ideal.

    There will also be an RCD module connected to the solar side for even additional protection. (mains already has RCD/ELB breakers)

    I will also be doing some extensive testing on the earth joining and testing with a portable RCD unit to make sure what im doing is safe. I think for the moment, keeping the earth across the entire system as one (noise isolated) net is better for safety.

    My thinking is that it would prevent the entire solar system floating above or below the house earth, and even with no fault present, the earth of a metal case connected to the solar system being different to the earth of the house and possibly causing a shock.

    The solar inverter and DC side of the bank is all connected together, and also earthed outside to a copper rod i bashed into the ground, but there is no direct connection between house earth and solar earth, which is to prevent the solar system from being dangerous in the event of a mains fault in the house.

    There are so many "things" to think of in this case. Do you directly join the earth of the solar system to the house earth? House earth is also neutral due to the MEN link, so that means the solar system is now connected to the grid through the virtual neutral.

    That means in the event of a neutral fault the entire solar system becomes live!
     
    Last edited: May 1, 2018
  2. shane41

    shane41 Member

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    LoL you guys are killing it with the knowledge :tongue: I just bought a solar unit that does everything contained in x1 box. Done finish :thumbup:
     
  3. Recharge

    Recharge Member

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    and that box was???
     
  4. shane41

    shane41 Member

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  5. rainwulf

    rainwulf Member

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    Interestingly enough, there is a diy ups project in the may edition of silicon chip that has dealt with the switching between two sources of ac in a similar way. They are using 2 relays to isolate the actual switching relay. Normal upses dont do this usually, as they often have the neutral as a common.
     
  6. MUTMAN

    MUTMAN Member

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    Why not use solid state relays ? Cost ?
     
  7. rainwulf

    rainwulf Member

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    Solid state relays fail closed, and have nowhere near the insulation resistance of air. They can also false trigger on transients. You dont want any of that bullshit happening with 2 different sources of 240 volts!
     
  8. hairy

    hairy Member

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    hey guys just after some input.
    I am making a little setup for my cb radio and possibly my linear amplifier (cb draws 1.5amps, linear draws 29amps).
    at the moment I am running my cb off 3x1000 cca truck batteries that I get for free from work (we replace them once a year so I just test voltage and take the good ones). unsure on amp hours.
    I run a trickle charger on the batteries once a week to keep them topped up and healthy even though I use the radio on 3 hours a week roughly.
    I run my linear off a 40a psu that I would like to run off my battery bank as I am only on radio at night once or twice per week.
    I have 11kw worth of solar on my roof atm to supply my house and garage.
    is it worth buying some panels and a charge controller for my setup or just sticking with the way I run it now and maybe adding more batteries ?
    wouldn't mind getting an invertor to run some other things in the shed either like my power tools and jukebox etc.
    this isn't about saving money more of a project as I'm bored lol.
     
  9. rainwulf

    rainwulf Member

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    Well, can you safely partition some of those solar panels to use in your own hybrid off grid system?
     
  10. hairy

    hairy Member

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    no they have to stay how they are.
    I could keep doing as I do know and just run the trickle charger off my 240 power point on a timer when the sun comes up and buy an invertor to run my radio equipment and some stuff around the shed.
    I wish it was as easy as just adding truck batteries to my house solar lol, I know illegal unsafe etc.
    just have a fair few truck batteries available and thought why not use them.
    I do have a fridge/freezer in my shed so I might try to run that too.
    off to ebay I trot !
     
  11. Recharge

    Recharge Member

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    I'd just stay with the timer, it's the cheapest option and functional.
     
  12. Sunder

    Sunder Member

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    I am on the cusp of getting a handful (60) of the below.

    I am getting them for about $27USD per cell. Will probably need to pay GST on that. So it's not as cheap as the other cells, but being flat, I can get them into my electric motorcycle.

    The "bulk buy" discount is tiny. 83c USD saved per cell if I go over 100 units, so I'm not that keen on running a group buy. But if there are some guys in Sydney who want a few samples at cost, to decide whether they want to get their own, I'm happy to buy a few extra.

    If someone wants 100 cells though, I'm not taking the risk by paying $2700USD for cells someone might end up saying "Sorry mate, changed my mind", and I doubt they'd want to take the risk by fronting up the cash.

    upload_2018-5-7_20-16-10.png
     
  13. rainwulf

    rainwulf Member

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    I want some of those bastard things.. dammit
     
  14. Sunder

    Sunder Member

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    Ordered these at 4pm, to beat the daily processing cut off. Should have them in 3 weeks or so.
     
  15. shane41

    shane41 Member

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    I already committed to Gel's ... so I'm set for a while Sunder. Going OK to ... keeping my modest setup running beyond midnight.
     
  16. OP
    OP
    Mathuisella

    Mathuisella Member

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    in your gearbox...grindin
    so 14 AH at 240V

    enough for about 5 hours of PC gaming after the sun has gone down, or perhaps an all nighter doing word processing :p Even longer if you're just doing laptop only instead of desktop
     
  17. shane41

    shane41 Member

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    Shit man must be a teeny weeny gaming pc. :tongue: The dual core & gtx 970 here pull 350watt on the inverter. + hot beer for the next 84 years :confused:
     
  18. Sunder

    Sunder Member

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    It's actually for an electric motorcycle. Around 50-60km, depending on what speed. Old battery was good for 100-120km, but I never went that far.

    The house battery is still a while off. I'm looking at 22kwh for that.
     
  19. Recharge

    Recharge Member

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