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  • CC and Load connected directly to battery terminals

    This is a basic setup where both the mppt CC & the fridge will be connected directly to the batteries terminals, the CC has no load output. Say a 250W portable panel.

    First off my understanding is that the fridge will draw power mostly from the CC in full sunlight & mostly from the Battery in overcast. In full sunlight with a topped up battery the current coming out of the CC wont go into the battery & should "bypass" the battery & be drawn straight to the fridge as the CC has the highest voltage & the fridge cables have the lowest resistance.
    Overall on a sunny day the battery should stay in a high SoC with low discharge cycles. If the load device starts to approach the panels amp rating even in full sunlight the battery SoC will drop.

    Is this all correct? If not please state exactly.

    But.

    What exactly happens if cc is in absorption or float and the fridge is turned on drawing the usual 3-4amps?

    Will the fridge get most of it's current from the CC while the CC is still able to monitor & maintain the battery in float?

    thanks

  • #2
    Does not work exactly that way, but you got the jest of it. The modes you speak of Bulk, Absorb, and Float are just catchy names for voltage set points. Once the battery is fully charged, the panels will supply power to the load assuming the demand does not exceed what the panels can generate. Otherwise the batteries make up the difference.
    MSEE, PE

    Comment


    • #3
      While you are connecting "directly" to the battery, I hope you are using a fuse for the size of wire installed, for fire safety.
      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


      • #4
        Originally posted by Sunking View Post
        Does not work exactly that way, but you got the jest of it. The modes you speak of Bulk, Absorb, and Float are just catchy names for voltage set points. Once the battery is fully charged, the panels will supply power to the load assuming the demand does not exceed what the panels can generate. Otherwise the batteries make up the difference.
        Thanks!

        Comment


        • #5
          Originally posted by Mike90250 View Post
          While you are connecting "directly" to the battery, I hope you are using a fuse for the size of wire installed, for fire safety.
          yes, but I guess I need more fuses in the +pos cable runs of my panels if I have two in parallel wired directly into PV input on CC. Also another fuse in fridge cable.
          fridge wire is only 14-16AWG which runs into an andeson plug & from there it's 6AWG straight to battery.

          Comment


          • #6
            image_10973.png The MRBF fuse block from Blue Seas is very handy for connecting a charge source (40A) and loads (120A) to two handy fuses
            https://www.bluesea.com/products/215...k_-_30_to_300A
            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
              Originally posted by Mike90250 View Post
              image_10973.png The MRBF fuse block from Blue Seas is very handy for connecting a charge source (40A) and loads (120A) to two handy fuses
              https://www.bluesea.com/products/215...k_-_30_to_300A
              Will look into that thanks.



              So I had some more time to think about this, I read how a typical CC doesn't measure the battery SoC & voltage is a very crude way to know SoC anyway.
              In an outdoor setup where you have the fridge constantly drawing from the battery, the battery chemistry won't have a chance to settle down for an accurate reading in morning. So I don't see how the CC can maintain the battery properly with a constant load. perhaps battery longevity is shortened?

              I assumed in float the CC can't supply the load as its current has reduced significantly, & when battery voltage sags from load (which could take hours with a fridge) it will kick back in to bulk supplying much of the load, but for battery health this would be inaccurate like reading a surface charge only. I dunno?
              My vehicle isolator looks to do the same at 12.7V it joins both batteries but it seems to judge this voltage point by the incoming alternator voltage, not the actual battery voltage which is usually lower by itself.

              Comment


              • #8
                Originally posted by Jman View Post
                So I had some more time to think about this, I read how a typical CC doesn't measure the battery SoC & voltage is a very crude way to know SoC anyway.
                In an outdoor setup where you have the fridge constantly drawing from the battery, the battery chemistry won't have a chance to settle down for an accurate reading in morning. So I don't see how the CC can maintain the battery properly with a constant load. perhaps battery longevity is shortened?
                Think of it like this. The best analogy is MONEY. Most off-grid solar systems operate like this. They start out with $1000 in the bank (battery) when they open the account (install the system). It cost them $300 per day to live, and their job pays $200 per day leaving a $100 per day deficit. In a week or two you go bankrupt. To go off-grid means some sacrifices. Most important sacrifice is you must live below your means, and earn more than you spend. Battery systems are sized to provide you 5 days of reserve which in practice give you 3 days of usable power. Panel power must be sized to generate two days of energy use in a single day.


                Originally posted by Jman View Post
                I assumed in float the CC can't supply the load as its current has reduced significantly,
                You assumed incorrectly. The charge controller does not control current, it controls voltage. The panels and battery control current passively by Ohm's Law.

                Originally posted by Jman View Post
                My vehicle isolator looks to do the same at 12.7V it joins both batteries but it seems to judge this voltage point by the incoming alternator voltage, not the actual battery voltage which is usually lower by itself.
                That is not how it works. First all newer vehicle alternators are set to a standard 14.2 to 14.4 volts. How the Isolator works depends on how it is designed. An inexpensive mechanical Isolator is just a relay that is controlled with the ignition switch. When the ignition is turned on, both batteries are connected, and when turned off the house battery is isolated. A inexpensive electronic Isolator is nothing more than a simple passive diode that only allows current to flow in one direction. Neither types controls current. Again current is controlled by the battery via Ohm;s Law, and the alternators voltage.

                In order for current to flow there must be a voltage potential difference between two points. Current = Voltage / Resistance. As the battery charges up, the voltage rises. When the battery voltage equals the supply voltage, no current flows.

                When you controller goes into Float mode only lowers the voltage to stop charging the batteries. Full power from the panels is still available if demanded.

                More Ohm's Law

                Power = Voltage x Current.

                So 1000 watts = 12 volts x 83.3 amps = 14.4 volts x 69.44 amps = 13.6 volts x 73.5 amps = 120 volts x 8.33 amps all day and night long.

                So if the batteries are charged by noon in Float at 13.6 volts, 1000 watt panel system, with bright sunny skies, and your refrigerator is drawing 200 watts, the panels supply all the power and the current would be Amps = Power / Voltage = 200 watts / 13.6 volts = 14.7 amps. The batteries just set there and Float which means they are not doing anything. If you system is designed correctly, essentially the batteries only supply power in the late afternoon and night.

                Last edited by Sunking; 05-10-2018, 02:12 PM.
                MSEE, PE

                Comment


                • #9
                  I've seen my charge controllers cranking 4000 watts while in float, and heavy loads are on. If you don't have enough panels, the difference is made up from the battery, just like at night.
                  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


                  • #10
                    Originally posted by Sunking View Post

                    That is not how it works. First all newer vehicle alternators are set to a standard 14.2 to 14.4 volts. How the Isolator works depends on how it is designed. An inexpensive mechanical Isolator is just a relay that is controlled with the ignition switch. When the ignition is turned on, both batteries are connected, and when turned off the house battery is isolated. A inexpensive electronic Isolator is nothing more than a simple passive diode that only allows current to flow in one direction. Neither types controls current. Again current is controlled by the battery via Ohm;s Law, and the alternators voltage.
                    I did post info about later model vehicle charging systems once before. They do not all put out 14+ volts, many will not work with standard type VSR as they can drop to low voltages.

                    Here is a snippet, this is from a Redarc site which has good info, there will be others.

                    #Fixed Voltage (always 14V or more from alternator during driving)

                    #Temperature Compensating (always 13.2V or more from alternator during driving)

                    #Variable Voltage Alternator (12.7V or less from alternator at any time during driving)

                    My two current new fords have variable alternators, they have basically a shunt on the negative post. All accessories added must be connected to chassis before the shunt or the ECU cannot detect the load and the battery will end up flat.

                    They will not work with standard VSR you need DC/DC chargers that work from low volt input.

                    Comment


                    • #11
                      Originally posted by Bala View Post

                      I did post info about later model vehicle charging systems once before. They do not all put out 14+ volts, many will not work with standard type VSR as they can drop to low voltages.

                      Here is a snippet, this is from a Redarc site which has good info, there will be others.

                      #Fixed Voltage (always 14V or more from alternator during driving)

                      #Temperature Compensating (always 13.2V or more from alternator during driving)

                      #Variable Voltage Alternator (12.7V or less from alternator at any time during driving)
                      You are contradicting yourself. You do understand you cannot charge a 12 volt battery a 12 volt battery at 12.7 or 13.2 volts right? Minimum voltage a 12 volt battery can be charged at is Float of 13.6 to 13.8 volts.

                      MSEE, PE

                      Comment


                      • #12
                        Originally posted by Sunking View Post

                        You are contradicting yourself. You do understand you cannot charge a 12 volt battery a 12 volt battery at 12.7 or 13.2 volts right? Minimum voltage a 12 volt battery can be charged at is Float of 13.6 to 13.8 volts.
                        I didnt make up the snippet info, there is no contradiction. I gave you this info on a pdf from the redarc site a few years ago when the forum was still happy with links.

                        You will need to study up on the later tech being used in the automotive industry. Ford Ranger PX2 is a good one to look at, I have one.

                        They have an ECU controlled Variable Voltage Alternator. They use a shunt type device on the negative terminal.

                        When the ECU senses that the battery has been recharged to 100% they will reduce voltage levels to save fuel / emissions.

                        I believe they may still supply required current to loads but without any more charge input to the battery than is required to keep it at full charge.???

                        I dont know the total technical deatils of the systems but they exist, a lot of people have been caught adding accessories and dual battery systems to later model vehicles.

                        I think a term used is smart charging and can be turned off on the Ranger.

                        I am also not saying it is a good thing for battery life or vehicle owner life in general. So far I have had no problems in 12 months and 30K km, but a lot of owners have.

                        Comment


                        • #13
                          This PDF provides some info on Variable Voltage Alternators.

                          http://jimbutterworth.co.uk/5batterycharging.pdf

                          Comment


                          • #14
                            Originally posted by Sunking View Post

                            Think of it like this. The best analogy is MONEY. Most off-grid solar systems operate like this. They start out with $1000 in the bank (battery) when they open the account (install the system). It cost them $300 per day to live, and their job pays $200 per day leaving a $100 per day deficit. In a week or two you go bankrupt. To go off-grid means some sacrifices. Most important sacrifice is you must live below your means, and earn more than you spend. Battery systems are sized to provide you 5 days of reserve which in practice give you 3 days of usable power. Panel power must be sized to generate two days of energy use in a single day.


                            You assumed incorrectly. The charge controller does not control current, it controls voltage. The panels and battery control current passively by Ohm's Law.



                            That is not how it works. First all newer vehicle alternators are set to a standard 14.2 to 14.4 volts. How the Isolator works depends on how it is designed. An inexpensive mechanical Isolator is just a relay that is controlled with the ignition switch. When the ignition is turned on, both batteries are connected, and when turned off the house battery is isolated. A inexpensive electronic Isolator is nothing more than a simple passive diode that only allows current to flow in one direction. Neither types controls current. Again current is controlled by the battery via Ohm;s Law, and the alternators voltage.

                            In order for current to flow there must be a voltage potential difference between two points. Current = Voltage / Resistance. As the battery charges up, the voltage rises. When the battery voltage equals the supply voltage, no current flows.

                            When you controller goes into Float mode only lowers the voltage to stop charging the batteries. Full power from the panels is still available if demanded.

                            More Ohm's Law

                            Power = Voltage x Current.

                            So 1000 watts = 12 volts x 83.3 amps = 14.4 volts x 69.44 amps = 13.6 volts x 73.5 amps = 120 volts x 8.33 amps all day and night long.

                            So if the batteries are charged by noon in Float at 13.6 volts, 1000 watt panel system, with bright sunny skies, and your refrigerator is drawing 200 watts, the panels supply all the power and the current would be Amps = Power / Voltage = 200 watts / 13.6 volts = 14.7 amps. The batteries just set there and Float which means they are not doing anything. If you system is designed correctly, essentially the batteries only supply power in the late afternoon and night.
                            Thanks sunking for that huge post. Helps clear this up some more. Not sure what you mean by "if your system is designed correctly"?
                            my system is just as simple as the charge controller and fridge both connected directly to battery terminals, all by quick relaese anderson plugs.

                            as for isolator, mine is not at all triggered by ignition, my alternator is temp compensate. Starts off at 14.1v then 20mins later down to 13.8v. Dont know if thats enough voltage to charge two big batteries in a 3-4hr drive.

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