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  • Batteries not performing as i expected

    I have a small solar powered system on an off grid cabin. I have one 80 watt panel, 550 amp hours of battery storage and a 1500 watt inverter. We have only a few lights (all 12 volts), two 12 volt water pumps, and a tv and a dvd player. Even with the batteries at 12.5-13.0 amps, when i turn on the tv and dvd player (no other power using items on), the battery levels drop down to 11.2 and sometimes triggers the alarms on the inverter. It seems like with the batteries at 12.5-13.0 they should easily be able to run the tv and dvd player. Or if the tv and dvd are playing and we turn on a light it will cut off sometimes as well. What am i missing?

  • #2
    Originally posted by cncshaw View Post
    What am i missing?
    A lot more solar panels, like 1000 W or so. What charge controller are you using?
    CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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    • #3
      You have a few problems.

      Working backwards a 12 volt 1500 watt inverter requires a 12 volt 1000 AH Battery.
      A 12 volt 1000 AH battery requires a 1000 watt solar panel with 80 amp MPPT controller.

      Working forward with your 80 watt panel and a PWM controller can only support 12 volt 40 AH Battery
      A 12 volt 40 AH battery can only support a 50 watt Inverter.

      So a complete mismatch is your first problem.

      But sounds like you have another problem, you wiring and connections, or possible a destroyed battery. Measure the voltage right on the battery post with the Inverter turned off. If you read 12.6 volts at dark outside, so far so good. Now turn on the inverter with a load like your TV and watch what happens to the battery voltage at the battery. If it stays at 12.6 all good so far. If the voltage drops on the battery like say 12 volts or less, the battery is a boat anchor. If the voltage holds up, measure the voltage right on the input terminals of the Inverter. The voltage should be roughly equal or with in 1/10th of a volt of the battery with a heavy load. Example if battery reads 12.6, you should see no less than 12.5 volts at the inverter at 1000 watt load. I suspect you TV is a very small load and you should not see any voltage drop at the inverter. If it is lower you have a wiring/connection problem.

      A 1500 watt 12 volt inverter should have a minimum 1/0 AWG copper cable, A 1/0 cable is about the size of a Cuban Cigar in diameter and weighs about 1 pound per foot.
      MSEE, PE

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      • #4
        Originally posted by sensij View Post
        A lot more solar panels, like 1000 W or so. What charge controller are you using?
        I will have to get the details of what charge controller I have the next time we go to the cabin, but i think its only a 10A controller.

        Comment


        • #5
          Originally posted by Sunking View Post
          You have a few problems.

          Working backwards a 12 volt 1500 watt inverter requires a 12 volt 1000 AH Battery.
          A 12 volt 1000 AH battery requires a 1000 watt solar panel with 80 amp MPPT controller.

          Working forward with your 80 watt panel and a PWM controller can only support 12 volt 40 AH Battery
          A 12 volt 40 AH battery can only support a 50 watt Inverter.

          So a complete mismatch is your first problem.

          But sounds like you have another problem, you wiring and connections, or possible a destroyed battery. Measure the voltage right on the battery post with the Inverter turned off. If you read 12.6 volts at dark outside, so far so good. Now turn on the inverter with a load like your TV and watch what happens to the battery voltage at the battery. If it stays at 12.6 all good so far. If the voltage drops on the battery like say 12 volts or less, the battery is a boat anchor. If the voltage holds up, measure the voltage right on the input terminals of the Inverter. The voltage should be roughly equal or with in 1/10th of a volt of the battery with a heavy load. Example if battery reads 12.6, you should see no less than 12.5 volts at the inverter at 1000 watt load. I suspect you TV is a very small load and you should not see any voltage drop at the inverter. If it is lower you have a wiring/connection problem.

          A 1500 watt 12 volt inverter should have a minimum 1/0 AWG copper cable, A 1/0 cable is about the size of a Cuban Cigar in diameter and weighs about 1 pound per foot.
          I didn't realize that the panel and charge controller would effect the performance of a fully charged battery. I figured that the panel and controller would only effect the rate at which the battery can recharge. I will check the voltage on the battery as you suggested above. If the volts stay around 12.6 then are you saying that my wiring may be undersized for what I am trying to do?

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          • #6
            The definition of "fully charged battery" changes over time. At first, you might have been OK. However, that 80 W panel produces at most 80 W / 12 V = 6.6 A, and usually less than that. 6.6 A into a 550 Ah battery is only C / 83. You want to be hitting at least C/20 (27.5 A), but probably more like C/10 (55 A) unless you have a gel battery that requires a slow charge. By charging it so weakly, what you are reading a "fully charged" isn't really, and over time, your battery is dieing. If you haven't used it long, a good EQ charge might save it (I think?), but until you can get the charge current up there isn't much future for it.

            The comment about undersized wiring is more anticipating how much current you really need, and guessing that your existing wiring won't be sufficient.
            CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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            • #7
              The Issue is related to battery, inverter or panel.
              Last edited by solar pete; 08-10-2015, 08:54 PM. Reason: spam

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              • #8
                Originally posted by arpit.v7 View Post
                the issue is related to battery, inverter or panel.this may help you in crosschecking and determining the fault. <links removed from quote.
                do not click this guys links. You have been warned.
                Last edited by inetdog; 08-09-2015, 02:45 PM.
                MSEE, PE

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                • #9
                  The current behavior of that web site is suspicious at best and malicious at worst.
                  Either the site has been hacked recently or it is deliberately set up to serve malware.
                  I am making the links uncliickable for now.
                  Thanks for the heads up SK.
                  SunnyBoy 3000 US, 18 BP Solar 175B panels.

                  Comment


                  • #10
                    Originally posted by inetdog View Post
                    The current behavior of that web site is suspicious at best and malicious at worst.
                    Either the site has been hacked recently or it is deliberately set up to serve malware.
                    I am making the links uncliickable for now.
                    Thanks for the heads up SK.
                    Oops. Too late for me. Those links take you to what looks like a Science Article on batteries with an advertisement at the bottom for some solar equipment.

                    I'll let you all know if my other computer gets corrupted by going to them.

                    Comment


                    • #11
                      Originally posted by cncshaw View Post
                      I have a small solar powered system on an off grid cabin. I have one 80 watt panel, 550 amp hours of battery storage and a 1500 watt inverter. We have only a few lights (all 12 volts), two 12 volt water pumps, and a tv and a dvd player. Even with the batteries at 12.5-13.0 amps, when i turn on the tv and dvd player (no other power using items on), the battery levels drop down to 11.2 and sometimes triggers the alarms on the inverter. It seems like with the batteries at 12.5-13.0 they should easily be able to run the tv and dvd player. Or if the tv and dvd are playing and we turn on a light it will cut off sometimes as well. What am i missing?
                      I have a 30 amp charge controller.

                      Comment


                      • #12
                        Originally posted by cncshaw View Post
                        I have a 30 amp charge controller.
                        Your underlying equipment matching issue is as SK stated in post #3. The 30A is not a limiting factor, because at 80W you won't get to even 10A.

                        Comment


                        • #13
                          Originally posted by SunEagle View Post
                          Oops. Too late for me. Those links take you to what looks like a Science Article on batteries with an advertisement at the bottom for some solar equipment.

                          I'll let you all know if my other computer gets corrupted by going to them.
                          Yeah, I got the odd behavior too. Not sure if I picked up anything. Ironically, the guy's user name looks like a virus.

                          Comment


                          • #14
                            Originally posted by Living Large View Post
                            Yeah, I got the odd behavior too. Not sure if I picked up anything. Ironically, the guy's user name looks like a virus.
                            It seemed he was legit based on his name at the top of the article which he wrote for that scientific journal. It was the links to advertisments at the end that I thought could be fishy but then let it go because you find those at the end of just about every technology website like EnergyBiz and RenewablesBiz which provide the latest in solar and RE news.

                            His article did do a pretty good job of explaining the difference in battery chemistry and their storage capabilities. But like a fly to a light those websites could draw in people before they get zapped. I will run a deep anti virus search tonight on my home computer.

                            I did check on the ScienceInfusion website and it does seem to be legit by allowing people to post or blog about scientific topics. Arpit Verma is one of the bloggers and according to the website has a BSME degree from India.
                            Last edited by SunEagle; 08-10-2015, 11:09 AM. Reason: added last sentence

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