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  • quit charging....voltage drops when connected to controller

    About 6 months ago I set up a solar system on my offroad teardrop trailer. It consists of a Suaoki 100W 18V 12V Solar Panel Charger, a Sun YOBA 20A 12V 24V Solar Charge Controller and a 12v wet lead acid battery all connected with 10 guage wire and MC4 connectors. It worked fine until a couple of weekends ago I pulled out the trailer to take it out and found the battery dead. I charged it using a 110 source with a charger. The solar controller showed that I wasn't getting sufficient voltage from the solar panel. I tested the wires coming directly from the panel and got ~15-17 volts, but the charge controller showed 9 or less. The battery was showing 12.4 volts When I connected my volt-meter to the charge controller connections to the solar I got that same less than 9 volts. Whenever I connect the solar panel to the charge controller the voltage coming out of the charge controller would drop. I assumed there was something wrong with the solar controller and replaced it with a HQST 30 Amp PWM Smart Solar Charge Controller with LCD Display but had the same problem. I have tried cleaning all of the connections and putting dielectric grease on them, it didn't help.

    What could be going wrong? is my panel going bad and making the voltage, but not enough amps to overcome resistance?

  • #2
    Sounds to me like you have killed your battery. Just because it shows voltage after you charged it means little. First 12.4 isn't indicative of a fully charged battery. 12.8 or 12.9 would be what you are looking for a couple days after charging it and allowing it to sit with no load or charging. Have you checked the electrolyte levels? The real test of flooded cell batteries would be done with a quality hydrometer. You need one to tell if your battery is shot, and to monitor your new batteries state of charge.
    2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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    • #3
      thanks llittleharbor. my battery could be bad, but wouldn't the charge controller still recognize that voltage from my solar panel and attempt to charge the battery? The charge controller is not attempting to charge the battery despite it being below the charge threshold set in the controller due to the low voltage it is getting from the panel. The battery may not be in great health, but it runs my LED lights and water pump fine.

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      • #4
        One other note, I noticed some small wrinkles in my panel. It is flexible and slightly bent over my trailer. See pics for details IMG_20180202_180756.jpg

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        • #5
          If your controller showed 9, or less volts it may not have been enough voltage to boot properly. You may have polarity crossed somewhere. I would still verify the battery is at the correct electrolyte level and holding a charge after sitting disconnected. If it passes those two items then first disconnect the solar panel, connect the battery, then reconnect the solar panel. Some controllers wont tolerate having solar connected without first having the battery hooked up.
          2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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          • #6
            sorry I forgot to mention I did verify the levels (had to add a little water) before charging. I have checked and there is no polarity issues. The battery has been disconnected for about a week and is still about 12.3 volts.I always connect the solar panels after the battery and the charge controller relies on the battery to boot, won't boot without a battery.

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            • #7
              Voltage on the battery is a little low but not enough to cause booting issues then. You may have a bad panel . Without a load on it a simple open circuit voltage measurement won't reveal some issues. Can you get a 12 volt load such as an extra 2 bulb RV light fixture? You can connect it with your panel and multimeter in full sun and see what the voltage does?
              2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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              • #8
                How many AH is the battery?, Car/RV size, or motorcycle batt?, a failing battery or a battery too large for your panel and/or conditons will sag the voltage when connected, just as a good condition fully charged battery will allow system to float and then you will see near open circuit voltage at the input of controller. Does your controller indicate what mode it is in? (bulk, float, etc.)
                Last edited by LETitROLL; 02-06-2018, 12:47 AM.

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                • #9
                  You mentioned you get 15 to 17 volts when checking panel directly, sounds to me like the battery is pulling it down.

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                  • #10
                    Sounds to me like you made the mistake (or something happened) and disconnected the battery from the charge controller while the panel as still hooked to the charge controller. If you need to disconnect the battery for any reason disconnect the panel first.

                    Disconnect everything. With the battery fully charged hook up the charge controller to battery first. Then hook the panel back up and recheck all the voltages.

                    WWW

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                    • #11
                      I tried connecting a simple test light to the panel directly in full sun and it does not illuminate. Works fine when connected to the battery.

                      I am anot sure the exact AH rating of the battery, but it is big....like a large car battery.

                      The charge controller just indicates that there is no charge coming into the battery from the panel. I have it set to start doing that at anything under 13.2 volts and stop load if the batter goes bellow 11.5 volts.

                      The Panel is connected with MC4 connectors. Everything else is hard wired into the controller. So I have disconnected the panel and re-connected it multiple times. with the battery connected.

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                      • #12
                        Can you get to the panel and try wiggling the leads coming out of it? I'm assuming the junction box is on the face of the panel as it looks to be a frameless flexible type.
                        2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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                        • #13
                          Originally posted by miahshodan View Post
                          I tried connecting a simple test light to the panel directly in full sun and it does not illuminate. Works fine when connected to the battery.
                          That pretty much narrows it down, seems that as i believe you mentioned in your first post that the panel shows a surface voltage when checked with a meter, but due to some sort of defect (cell damage,crack, bad connection, etc.), as soon as any load is applied it cannot pass enough/any current and the voltage crashes. Fairly common problem with various types of damaged/defective panels.

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                          • #14
                            I contacted the panel maker (Suaoki) and they asked for pictures of how I was measuring and the results. But when I went to do it, I could not replicate them. Now the test light lights up, but the panels make 9-10v in full sun regardless of load. I can't imagine what changed....there isn't a whole lot to it. I am connecting my volt-meter directly to the leads with nothing else involved.
                            Attached Files

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                            • #15
                              9-10 volts would be 1/2 of the open circuit voltage, indicative of possibly, a bad diode or other damage cutting out 1/2 the panels cells.
                              2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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