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  • New at this

    I need some advice as this is my first try at installing a solar panel.
    I want to install an address at the end of my driveway, it will be back lite with a 0.72w led.
    I purchased a 25W solar panel and a small controller from the internet. I am in the process of testing it all before I do a permanent installation.
    I have two batteries one is 4.5AH and the other one is 7AH. When I first started the tryout I first charged both batteries with a battery charger, when that was done, the controller's status light was green indicating that the batteries were fully charged.
    Since then, I only had two days were after running the led for only 6 hours the status light would come back green and now its always red.
    I don't understand, I'm thinking its probably the cheap controller ?
    Can anyone look at the pictures, I would really welcome the input.
    0.72W Led.jpgBig Battery.jpgSmall Battery.JPGControler.jpgSolar Panel.jpg

  • #2
    The charge controller probably consumes almost as much as the light does on a daily basis. Your 20W panel with PWM can only produce about 12W. Add some clouds and you will be lucky to get 3W. The batteries don't match so I assume they are used and don't have the capacity you expect. The worst issue is the panel size.


    • #3
      I don't understand, a 25W solar panel is not sufficient for a led of 0.72W that runs for only 6 hours a day? So how big of a solar panel would I need for such a puny light?


      • #4
        Is 20W enough? How would I know, it depends on where you live and if having an address
        light not work for a couple days is a BFD. I have 560W of panels I use for testing. I'd
        be thrilled if I could get 20W out of them mid day. The only real concern is not to damage
        the battery. All I know is you are not happy with the system as it is currently configured.
        You can handle the math. I'm not concerned about that. To start, disconnect the panel and
        connect it to the 10A range of the meter. Is that a number you can live with on a cloudy day?
        Charge the battery externally and see how many hours you get. You never want to drop below 10V.
        You have all the answers.


        • #5
          PNP. Sorry but that was a crap answer. Im new here and I realize this is an old post. But I know little about solar and was turned to this forum from FB. The question to me seems valid. 20w panel won


          • #6
            Originally posted by Cameo View Post
            I don't understand, a 25W solar panel is not sufficient for a led of 0.72W that runs for only 6 hours a day? So how big of a solar panel would I need for such a puny light?
            It is overkill. Ignore PNP he does not know what he is talking about.

            0.72 watts x 8 hours = 5.76 watt hours. All that is requires is a 10 watt panel which is still a bit large, smallest cheapest PWM charge controller you can find, and a battery no smaller than 5 AH for 5 day run time, and no larger than 10 AH.

            A 25 watt panel is fine. grossly large but will work, and only requires the smallest cheapest PWM controller you can find. Just do not use a battery smaller than 10 AH so you do not burn it up, and no larger than 17 AH or else it may not charge fully. Avoid using parallel batteries. No need to ever parallel batteries, and it you do will cut service life in half for the batteries.
            Last edited by Sunking; 04-11-2018, 04:48 PM.
            MSEE, PE