50W off-grid testing unit

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  • bctps55
    Junior Member
    • Nov 2010
    • 2

    #1

    50W off-grid testing unit

    Below is my system spec:

    Solar Panel: 46W (24V Voc; 18V Vm; 3.23A Iac; 2.43A Im)
    20W (22V Voc; 16V Vm; 1.40A Iac; 1.06A Im)
    Battery: 12V33AH AGM DC battery
    Charger: Steca PR1010 PWM SOC charge controller
    Load: 18W CFL bulb

    I have problem with the charging. Is it my setting problem or the charger controller?

    First, I fully charged my battery to 100% via regulator and rest it for a day. Then I connected it to the charge controller, however it read 80% in the SOC. Next, I discharge it with a bulb for 16hr and it drop to 62%. It seem the charger is working correctly, but when I recharge the battery using 50W solar panel via charge controller for 6hr with good sun radiation, the SOC only raised up to 64%.

    Next, I charged back the battery to 100% via regulator and rest it for a day. I then connected it to the charge controller again and then reset to factory setting and it show 80% charged as usual. Discharge to 62% with a bulb and try to recharge with 20W solar panel via charge controller. This time, after 6hr, the percentage drop to 60%. Why is that? Anyone have idea? Thx!
  • Sunking
    Solar Fanatic
    • Feb 2010
    • 23301

    #2
    When you say fully charged with a regulator, that is not clear to me. Do you mean fully charged with an AC powered battery charger?.

    OK assuming you have everything wired up correctly 54 watts of panel wattage is sufficient to charge a 12 volt 33 AH battery.

    How old is this battery? What bothers me is you say you fully charge it up, then place it on the charge controller and it reads 80% SOC. This leads me to believe you have a bad battery.

    Take some voltage measurements during mid day Sun and read the voltage at the input and output of the CC. If possible measure the input and output current.

    After you charge the battery up and let it rest what is the voltage at rest?
    MSEE, PE

    Comment

    • bctps55
      Junior Member
      • Nov 2010
      • 2

      #3
      Thanks Dereck for reply.

      The AGM battery is newly bought for around 2wks ago.
      Yes, I use a AC to DC regulator to charge the battery using 13.8V(regulator) and when reach 12.5V (battery), I used 15V(regulator) to charge up to 12.86(battery). Then I let it rest for 1day and it show 12.72V. I am not sure whether 12.72V is fully charged but I assume it is.

      However, I connected to the charge controller and it show only 80% charged.

      Comment

      • Sunking
        Solar Fanatic
        • Feb 2010
        • 23301

        #4
        OK if you used a regulated 13.8 volt power supply, that is a float algorithm which is just fine especially if the battery is used for emergency only. Question is how long did you let it float charge. Give it a float charge for 24 hours or longer.

        12.7 rested for several hours and disconnected is 100% charged. Does your CC have a switch or software to select battery type? Double check it is set to AGM, and not FLA or Gel.

        OK if you operated a 18 watt CFL which probable draws 20 watts from the battery for 16 hours = 320 watt hours. Your battery capacity is only 12 volts x 33 AH = 396 watt hours. You way over discharged the battery and possible damaged it. 320 wh / 396 wh x 100 = 82% DOD. You never want to discharge more than 50%, and no more than 20% daily.

        With only a 54 watt solar panel wattage, depending on your location this time of year, the panels can only generate 70 to 150 watt hours per day. Your test exceeded you panel and battery capabilities. So I am not surprised with your results, that is what I would expect.

        Where are you located?
        MSEE, PE

        Comment

        • russ
          Solar Fanatic
          • Jul 2009
          • 10360

          #5
          Hi bctps55 - Welcome to Solar Panel Talk!

          Looking forward to your participation!

          Russ
          [SIGPIC][/SIGPIC]

          Comment

          • melody

            #6
            Originally posted by Sunking
            OK if you used a regulated 13.8 volt power supply, that is a float algorithm which is just fine especially if the battery is used for emergency only. Question is how long did you let it float charge. Give it a float charge for 24 hours or longer.

            12.7 rested for several hours and disconnected is 100% charged. Does your CC have a switch or software to select battery type? Double check it is set to AGM, and not FLA or Gel.

            OK if you operated a 18 watt CFL which probable draws 20 watts from the battery for 16 hours = 320 watt hours. Your battery capacity is only 12 volts x 33 AH = 396 watt hours. You way over discharged the battery and possible damaged it. 320 wh / 396 wh x 100 = 82% DOD. You never want to discharge more than 50%, and no more than 20% daily.

            With only a 54 watt solar panel wattage, depending on your location this time of year, the panels can only generate 70 to 150 watt hours per day. Your test exceeded you panel and battery capabilities. So I am not surprised with your results, that is what I would expect.

            Where are you located?
            yes quite right, a PWM float charge progress need at least 1 and half hours as to our epsolar controllers, even though it read 100% full, it is really not.

            Comment

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