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Lights for 20w solar panel

Comments

  • #2
    unkel
    Registered Users Posts: 64,703 ✭✭✭✭unkel


    That's a 12V panel, so I presume you also have a 12V battery connected to your controller? There is a direct output from your controller for a load (the two right most screw in terminals), you can connect any 12V DC lights to it. If you want them to come on after dark, you will need a dawn to dusk sensor too


  • #3
    [Deleted User]
    Posts: 5,238 ✭✭✭[Deleted User]


    20W!?!!!!

    Advice...think big!


  • #4
    freddyuk
    Registered Users Posts: 1,110 ✭✭✭freddyuk


    unkel wrote: »
    That's a 12V panel, so I presume you also have a 12V battery connected to your controller? There is a direct output from your controller for a load (the two right most screw in terminals), you can connect any 12V DC lights to it. If you want them to come on after dark, you will need a dawn to dusk sensor too


    That controller has an in built timer so you can set it to come on for X hours after sunset etc.


    However Sir Liamalot is correct as the panel will never keep up with the load.
    Say the lamps are 3w each so you have 25 watts total load. Add 20% for losses and multiply by the number of hours you want them on then divide by 12(v) to get the amps load. Say 15 amp hours per day. If the panel is 0.5 amps (in full sun) you can work out how long it will take to re charge the battery ie. not in one day ever. So the battery will eventually run out of power. You need enough solar to cover the load each day to be sure the battery can manage it. A 100ah battery will give you maybe 3 days of lighting if there is no sun using recommended 50% DOD. So you need to design the system based on the time the lights are on/ wattage of the lights/ number of lights/size of solar panel/ size of battery/ cabling losses/ reserve power (latency) etc. etc. Much more complicated than you think to get it right but if it is right then it will work until your reserve capacity limit is reached which is all down to the weather. That is why you need to overkill the solar input........but in your case the project is not mission critical so if the lights go out so be it.


  • #5
    wannabecraig
    Registered Users Posts: 761 ✭✭✭wannabecraig


    Sir Liamalot wrote: »
    20W!?!!!!

    Advice...think big!

    Ha, thought I was getting a 50w. I honesty dont know anything about the panles and I dont know what 20w is event gonna do for me tbh


  • #6
    wannabecraig
    Registered Users Posts: 761 ✭✭✭wannabecraig


    freddyuk wrote: »
    That controller has an in built timer so you can set it to come on for X hours after sunset etc.


    However Sir Liamalot is correct as the panel will never keep up with the load.
    Say the lamps are 3w each so you have 25 watts total load. Add 20% for losses and multiply by the number of hours you want them on then divide by 12(v) to get the amps load. Say 15 amp hours per day. If the panel is 0.5 amps (in full sun) you can work out how long it will take to re charge the battery ie. not in one day ever. So the battery will eventually run out of power. You need enough solar to cover the load each day to be sure the battery can manage it. A 100ah battery will give you maybe 3 days of lighting if there is no sun using recommended 50% DOD. So you need to design the system based on the time the lights are on/ wattage of the lights/ number of lights/size of solar panel/ size of battery/ cabling losses/ reserve power (latency) etc. etc. Much more complicated than you think to get it right but if it is right then it will work until your reserve capacity limit is reached which is all down to the weather. That is why you need to overkill the solar input........but in your case the project is not mission critical so if the lights go out so be it.

    Thanks. This is some good info. Can I daisy-chain the panels, so buy a 80w for a total of a 100w system?

    Also, can you link me to lights that might work with this?


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  • #7
    [Deleted User]
    Posts: 5,238 ✭✭✭[Deleted User]


    Here's 110W for £24 ask if they'll ship to Ireland


  • #8
    wannabecraig
    Registered Users Posts: 761 ✭✭✭wannabecraig


    The dont ship but I can get something from Amazon. Do I just plug both panels into the same controller?


  • #9
    unkel
    Registered Users Posts: 64,703 ✭✭✭✭unkel


    Sir Liamalot wrote: »
    Here's 110W for £24 ask if they'll ship to Ireland

    Link doesn't work. What is it?


  • #10
    wannabecraig
    Registered Users Posts: 761 ✭✭✭wannabecraig


    Kr857di.png?1


  • #11
    unkel
    Registered Users Posts: 64,703 ✭✭✭✭unkel


    If that really is 110W, that's a bargain. Probably a misprice. All gone now, or do you have a link? I'd pick up a few myself.

    Mind, I have bought 100W panels from China before that were only about 12W. No surprise that I demanded and eventually got a full refund, without having to return them.


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  • #12
    wannabecraig
    Registered Users Posts: 761 ✭✭✭wannabecraig


    Yeah, link was gone very quickly. Not working now.

    Still no suggestions for lights though!


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