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  • This is ADDICTING, but I need HELP!

    I decided to jump in the solar power arena by trying to build my own "small" system to learn parts and process. I built a system to run an exterior security light at night on my property. Problem is that the system goes out after a few minutes of operation. here's my set up:

    40w Solar panel (w/ Solar Extension Cable 10 AWG PV Wire With MC4 Connectors)
    12v Marine Deep Cycle battery with 750 cranking amps (about a year old, but is taking charge and drives other items - like my boat motor)
    20A 12/24V Auto Switch PWM Solar Panel Battery Charging Controller
    175 w power inverter 20' extension cord
    27w LED screw in light bulb


    After a couple of minutes of successful operation - the inverter/convert alarm goes off, the red light comes on, and the Security light goes out. On the Charge Controller - the Solar Panel indicator light remains green, but the battery indicator light turns red?

    Any ideas?? Is my Inverter/converter bad?

    thanks for any and ALL HELP!!!

    Stacy

  • #2
    Originally posted by cankx2 View Post
    I decided to jump in the solar power arena by trying to build my own "small" system to learn parts and process. I built a system to run an exterior security light at night on my property. Problem is that the system goes out after a few minutes of operation. here's my set up:

    40w Solar panel (w/ Solar Extension Cable 10 AWG PV Wire With MC4 Connectors)
    12v Marine Deep Cycle battery with 750 cranking amps (about a year old, but is taking charge and drives other items - like my boat motor)
    20A 12/24V Auto Switch PWM Solar Panel Battery Charging Controller
    175 w power inverter 20' extension cord
    27w LED screw in light bulb


    After a couple of minutes of successful operation - the inverter/convert alarm goes off, the red light comes on, and the Security light goes out. On the Charge Controller - the Solar Panel indicator light remains green, but the battery indicator light turns red?

    Any ideas?? Is my Inverter/converter bad?

    thanks for any and ALL HELP!!!

    Stacy
    1. Way too much resistance in the 20 foot power cord, most likely.
    The inverter will probably need to suck at least 36 watts between idle current and 27 watt load. That would be 3 amps at 12 volts.
    If the cord is too small, a voltage drop of only 2 volts could cause the inverter to shut off.
    Are the DC cord or any of its connection points getting hot? Resistance increases with temperature.
    Do not use alligator clips or other weak connection to the battery.

    You can check this by putting a voltmeter on the DC side of the inverter to see what voltage it is getting at the end of the wire.

    2. If the inverter shuts off on its own without the LED lamp turned on, it may be a defective inverter. See from the manual what the Security light is supposed to indicate.

    3. But, since the battery light on the charger goes red too, chances are that the battery voltage is just going off a cliff. Possibly one bad or unbalanced cell so that the voltage drops from 12 to 10 or less after being loaded for a short time. DC loads like the boat motor could continue to work fine at the lower voltage from just the remaining cells as long as the battery can supply the current.
    SunnyBoy 3000 US, 18 BP Solar 175B panels.

    Comment


    • #3
      Two problems.
      • Not near enough panel wattage.
      • Battery is toast, wrong type, and deficit charging destroyed it.


      You have a 40 watt panel and a PWM controller which turns your 40 watt panel into a 25watt panel.

      To run a 27 watt light all night for example say 12 hours requires 27 watts x 12 hours = 325 watt hours. Using a PWM charger requires your panel to generate 750 watt hours. A small 40 watt panel with PWM can only generate with 3 to 5 Sun Hours is s roughly 25 watts x 3 hours = 75 watt hours, up to 25 watts x 5 hours = 125 Watt hours. You need 325 or more usable watt hours or more or about 7-cents worth of electricity. You are not even close.

      What it will take assuming you get a generous 4 Sun Hours with a PWM controller is:

      200 watt panel
      PWM Controller = 15 amps
      12 Volt Battery Capacity = 135 AH Deep Cycle

      If you use a MPPT charger it will take:

      125 watt panel
      MPPT CC = 15 amps
      12 Volt Battery Capacity = 135 AH Deep Cycle

      So you need an upgrade and replace your battery and panel.

      Good Luck.
      MSEE, PE

      Comment


      • #4
        Dawg do the math. 27 watt light, 40 watt panel, pwm controller, and inefficient inverter. It is way more than a long cable to inverter. 2 or 3 amps on a lamp cord for 20 feet is not the real problem. It is simple math and physics of Watthours
        MSEE, PE

        Comment


        • #5
          Originally posted by Sunking View Post
          Dawg do the math. 27 watt light, 40 watt panel, pwm controller. It is way more than a long cable and inverter. 2 or 3 amps on a lamp cord for 20 feet is not the real problem. It is simple math and physics of Watthours
          I was going by the assertion that the battery was able to run other loads. Possibly that was back before it ran down from undercharging.
          But if it will only run the light for a few minutes right now, then as you say it is now toast. The simple test for that is to try it with the boat motor without putting it on an AC charger first.

          The 27 watt load by itself does not mean anything unless we know how many hours a night the OP tries to run it.
          Since it was described as a security light, you are right in taking a first cut with it being on all night as read by the charger/controller.

          And, of course, regardless of the load, a 40 watt panel and PWM will not do well with a 70-80AH battery.

          I guess I need to keep looking for horses and not zebras.
          SunnyBoy 3000 US, 18 BP Solar 175B panels.

          Comment


          • #6
            Originally posted by Sunking View Post
            You have a 40 watt panel and a PWM controller which turns your 40 watt panel into a 25watt panel.
            Why is this, I am having trouble understanding is all, I may have made a mistake on my small system by using a PWM.

            Is is
            PV voltage - battery voltage
            difference x amps = lost watts?

            Comment


            • #7
              Originally posted by solarIdiot View Post
              Why is this, I am having trouble understanding is all, I may have made a mistake on my small system by using a PWM.

              Is is
              PV voltage - battery voltage
              difference x amps = lost watts?
              Yes.

              We do not know the voltage of your panel, but if it was designed for use with a PWM controller and a 12 volt battery, it will not be more than about 18 volts (Vmp) and you will be losing only 1/3 of your power.
              If it is the wrong type of panel (say Vmp =36 volts, suitable for charging a 24 volt battery) then you will be losing most of your power.
              SunnyBoy 3000 US, 18 BP Solar 175B panels.

              Comment


              • #8
                Originally posted by inetdog View Post
                Yes.

                We do not know the voltage of your panel, but if it was designed for use with a PWM controller and a 12 volt battery, it will not be more than about 18 volts (Vmp) and you will be losing only 1/3 of your power.
                If it is the wrong type of panel (say Vmp =36 volts, suitable for charging a 24 volt battery) then you will be losing most of your power.
                Ok thanks Inteldog, that's what I have taken to calling you Short for intelligence DAWG.

                This is the system I am referring to http://www.solarpaneltalk.com/showth...rid-Boat-House

                The smaller system you'll see the wife shut my grand idea down. Probably for the best!

                Sorry if I am hijacking this thread, if I am out of line please let me know!

                Comment


                • #9
                  Originally posted by solarIdiot View Post
                  Why is this, I am having trouble understanding is all,
                  Because with PWM Input Current = Output Current

                  A typical 12 volt battery panel has a Vmp of 18 volts. So a 40 watt battery panel woul dhave 18 volts @ 2.2 amps going into a 12 volt battery. 2.2 amps x 12 volts = 26 watts.
                  MSEE, PE

                  Comment


                  • #10
                    1st) Thanks for all the conversation...and no problem ID10T...I welcome the sidebars!!
                    2nd) I do not have alligator clips, and no increased temp have been experienced
                    3rd) I am away from the set up at the moment, so i can't change anything today and respond on it's performance yet...should be a week before I get back to it now.
                    4th) I do not understand the comment, "Battery is toast, wrong type, and deficit charging destroyed it."? What Type should I have?


                    thanks!!

                    Comment


                    • #11
                      Originally posted by cankx2 View Post
                      1st) 4th) I do not understand the comment, "Battery is toast, wrong type, and deficit charging destroyed it."? What Type should I have?
                      Go have a look in the Off-grid section of the forum. There are quite a few good stickies to read about designing for off-grid.
                      There is also an article that Sunking has written there that explains the difference between the battery types. Start there first, and if you have any questions after reading it a few times, then shoot away. Always good to read the stickies first!

                      Comment


                      • #12
                        Originally posted by cankx2 View Post
                        and no problem ID10T...I welcome the sidebars!!
                        Thanks Cankx2! I hope everything works out on your system

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