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  • Inverter connection: Battery or Load

    I'm looking for advice where to connect DC/AC inverter: directly to battery or to the LOAD on charge controller?
    What is the pro and con for each connections?

    Thanks,
    Key
    Last edited by monogram; 04-10-2018, 07:05 PM.

  • #2
    Direct to battery. Never use the Load Terminal as it is for very low power only.
    MSEE, PE

    Comment


    • #3
      Most charge controllers have a low amp capable at the Load Terminals. It is easy to over load it and burn something up.

      The safer place to connect the inverter would be on the battery terminals and use a fuse to protect the wire. Size the wire and fuse based on the Inverter wattage divided by the battery voltage. That is one reason we try to discourage people from using 12volt 2500 watt inverters. They can draw over 200 amps which can easily burn up a wire not rated that high.

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      • #4
        Usually only the smaller cheaper controllers have a load control function and load terminals. The max load is never more than the amp rating of the controller, but can be a lower amp rating. The purpose of the load control function is twofold. first it will disconnect the load if the battery voltage gets below a preset level, saving the battery from damage. Second they are typically meant to control a lighting circuit. They are triggered to turn on the lights at dusk and run them for a preset amount of hours. Anything heavier than a simple lighting circuit needs to come off the battery buss if you have one or direct from the battery otherwise.
        2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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        • #5
          • Since my load is running 24 hrs with only 100W or less, can I install 600W inverter directly to charge controller?

          I don't want to install the load to the battery because there is no option for me to auto shut down the battery if it get too low; if I connect the inverter to controller then I can set the controller to disconnect the battery when it hit 24.1V and the relay will switch to Normally Close to use 110AC from home power.

          if it's bad idea then any other recommendation?

          2018-04-11_114536.jpg
          Last edited by monogram; 04-11-2018, 02:48 PM.

          Comment


          • #6
            unless your controller specifies a Load rating higher than your load, I would NOT connect even a small inverter to it. Most are only a couple amps

            But the scary thing in your schematic, is the RELAY you show connected to AC What powers the coil of it? You show the DC input being wired to the AC electrical supply?
            If you have AC electrical, why solar, use a AC battery charger, unless you have weekly outages

            The inverter is powering a motor, so it should really be a pure sine wave inverter, motor runs cooler and lasts longer, and consumes less power from the inverter/battery
            Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
            || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
            || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

            solar: http://tinyurl.com/LMR-Solar
            gen: http://tinyurl.com/LMR-Lister

            Comment


            • #7
              unless your controller specifies a Load rating higher than your load, I would NOT connect even a small inverter to it. Most are only a couple amps
              What is the purpose for the load on controller if it not design to allow the load? What will happened if I'm using it?

              But the scary thing in your schematic, is the RELAY you show connected to AC What powers the coil of it? You show the DC input being wired to the AC electrical supply?
              If you have AC electrical, why solar, use a AC battery charger, unless you have weekly outages
              The DPDT relay coil #1 is powered by 24V from MPPT load and 24V also connected to pin 3 & 4.
              The second DPDT relay coil is power by 24V from MPPT load.

              When the battery is 24V or above, the relay will turn ON to provide 24V to inverter to convert 24V DC to 110V AC to power the pump.

              There also another DPDT relay switch working in parallel with the first switch, this relay coil is powered by 24V from controller. When the battery is 24.1V or above, the relay will switch to NO which connect to NOTHING.

              When the batteries voltage above 24.1V, the controller turn ON the 24V load which will:
              • Trigger the relay # 1 to turn ON the coil that will switch to NO position that connected to 24V; the inverter is now running to provide 110VAC to power the pump.
              • Trigger the relay # 2 to turn ON the coil that will switch to NO position which connect to NOTHING.

              When the batteries voltage drop below 24.1V, the controller will turn OFF the load which will:
              • Trigger the relay #1 to turn OFF the coil that will switch to NC which connect to NOTHING
              • Trigger the relay #2 to turn OFF the coil that will switch to NC which connected to 110VAC home power ==> to power the pump

              The inverter is powering a motor, so it should really be a pure sine wave inverter, motor runs cooler and lasts longer, and consumes less power from the inverter/battery
              Yes, it's pure sine wave, I will be using APC UPS battery backup as inverter (remove the internal battery and connect to 24V from MPPT load, no AC connect to UPS)

              I hoped this make sense and works as expected.
              Last edited by monogram; 04-11-2018, 04:34 PM.

              Comment


              • #8
                Originally posted by monogram View Post
                What is the purpose for the load on controller if it not design to allow the load? What will happened if I'm using it?
                SMOKE!

                You have a hard time with reading comprehension based on this post and your other post. Your question was answered in detail and yet you do not want to hear it.

                Only cheap controllers come with a Load Terminal and they are low power low current ports made for night lights. The Load Ports can only handle small currents of 5 amps or less. Hate to tell you unless your inverter is 40 watts or less will burn up the Load Ports. A 100 watt Inverter uses 10 amps at 12 volts. Got a 1000 wat Inverter now you need 100 amps.

                So please by all means connect your Inverter to the Load Port and learn the hard way if you cannot read and understand the answers.

                Now what you can do is use the Load Port to operate a relay, but I am not going to show you how.
                Last edited by Sunking; 04-11-2018, 04:56 PM.
                MSEE, PE

                Comment


                • #9
                  Originally posted by Sunking View Post

                  SMOKE!

                  You have a hard time with reading comprehension based on this post and your other post. Your question was answered in detail and yet you do not want to hear it.

                  Only cheap controllers come with a Load Terminal and they are low power low current ports made for night lights. The Load Ports can only handle small currents of 5 amps or less. Hate to tell you unless your inverter is 40 watts or less will burn up the Load Ports. A 100 watt Inverter uses 10 amps at 12 volts. Got a 1000 wat Inverter now you need 100 amps.

                  So please by all means connect your Inverter to the Load Port and learn the hard way if you cannot read and understand the answers.

                  Now what you can do is use the Load Port to operate a relay, but I am not going to show you how.
                  Hi Sunking,
                  I'm not saying that I don't want to hear what other users or Mike said but I just want to understand why I can't use the load port to power my 100W device, that is why I'm here to learn. I'm not a type of person that "just do it", I have to understand why before I do. I just don't want the hear the answer "don't do, it will SMOKE", all I want is an explanation.

                  Before joining this forum, I have been running my devices out of the load port for up to 7A at 25V (using PWR controller) for about 5 years but I don't see any issue at all that is Why I'm asking why I can't use the load port.

                  I'm feeling sad when you said you know how to but you don't want to share.
                  but thanks for this wording "use the Load Port to operate a relay"

                  I think this is what you mean: instead of getting 24V from load for interter (pin 7-3 and 8-4), now getting 24V from battery (pin 3 to battery "-" and pin 4 to battery "+" ) while the relay coil is connect to load.




                  Last edited by monogram; 04-11-2018, 07:07 PM.

                  Comment


                  • #10
                    Originally posted by monogram View Post

                    Hi Sunking,
                    I'm not saying that I don't want to hear what other users or Mike said but I just want to understand why I can't use the load port to power my 100W device, that is why I'm here to learn. I'm not a type of person that "just do it", I have to understand why before I do. I just don't want the hear the answer "don't do, it will SMOKE", all I want is an explanation.
                    Your question was answered in detail many times like your other thread.

                    I will not tell you how to use a relay because I do not want to explain it 20 times. I will tell you this. The Load Terminal on your controller is what is commonly called a Low Voltage Disconnect which is self explanatory. Very simple device, a small low current relay with a SPST contact that connects the controller Output (battery) to the Load Terminal. When battery voltage gets low, the relay coil operates and disconnects the Output from the Load Terminal.

                    That's all folks, I am done.

                    MSEE, PE

                    Comment


                    • #11
                      There is a little transistor in the controller, that enables/disables the LOAD connections. Generally as cheap and small as they can manage. If you have had success with using it in the past you were lucky. Some Mid-grade controllers have load connections that are rated same as the output port, but only about 3 models that I know of.
                      http://www.midnitesolar.com/productP...tOrder=1&act=p 30A
                      https://www.morningstarcorp.com/products/sunsaver-mppt/ 15a



                      Tutorial
                      https://itp.nyu.edu/physcomp/lessons...current-loads/
                      Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                      || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                      || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                      solar: http://tinyurl.com/LMR-Solar
                      gen: http://tinyurl.com/LMR-Lister

                      Comment


                      • #12
                        If you use a relay, put a diode, 1N4001 would be OK for 24V, across the relay coil, with the cathode on the positive end of the coil, so that it doesn't screw up something in the charge controller when de-energized (google "flyback diode").
                        Last edited by sdold; 04-11-2018, 10:04 PM.

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