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  • Feeding a power solar controller with a regulated power supply

    I just made an offer on a Renogy 30 amp PWM solar power controller. This Spring and Summer I plan to add a few hundred watts of solar panels to my backup system. In the meantime, I am charging the battery bank with a regulated power supply.

    I plan to experiment by connecting my 13.8 volt power supply to the solar input of the Renogy, the battery bank to batteries, and my 1Kw inverter to the load. (I currently have only one 105 AH marine battery, brand new. I plan to add one the first week of December. )

    My theory is that the controller will keep the DC voltage at or above 12.5 volts, but it may not be enough to keep the batteries capped off at their maximum level.

    Has anyone ever tried this configuration? What is your experience?

    If you use controllers (not attached to a regulated power supply) what does your experience or tech knowledge expect my results to be?


  • #2
    Your theory is wrong. To float charge a battery requires 13.8 volts, not 12.6 as 12.6 volts is an Open Circuit Voltage of a charged battery. If you have a 13.8 volt ham radio power supply, the PWM controller buys you nothing. The minimum foward voltage drop on a PWM controller is 1 volt. 13.8 - 1 = 12.8 volts. It takes a minimum 13.2 to 13.8 volt source depending on what alloy the Pb battery is. Quit geting your info from QRZ. Ideally you need a 18 volt source to charge a 12 volt battery. Solar panels are not voltage sources, they are current sources.

    73's
    MSEE, PE

    Comment


    • #3
      Originally posted by n4pgw View Post
      I plan to experiment by connecting my 13.8 volt power supply to the solar input of the Renogy, the battery bank to batteries, and my 1Kw inverter to the load. (I currently have only one 105 AH marine battery, brand new. I plan to add one the first week of December. )
      No need for the controller then. 13.8v from the supply is a float charge, and is actually too high for long term float anyway. Long term at 13.8v is a recipe for positive grid corrosion. 13.4 - 13.6v is where you want to be - for total long term float - but yes 13.8v initially to get to a full (and laboriously long) charge in the first place, then drop back to say 13.4 - 13.6.

      Don't make your Astron go bang, as it is not designed to be a battery charger. Oh, you'll get away with it *as long as the battery is NOT discharged too much*, but if it is, BANG. Usually guys don't find this out for years when they do a float on fully charged battery in the first place. First discharge and reapplication of AC - Pow.

      Do NOT add batteries after the fact. In fact, paralleling even when new is something to avoid if you can, unless you want to spend some quality maintenance time figuring out why one is acting better / worse than the other. TWO of the same age/usage, manufacturer, capacity, build-date is about the best case, and even then, you have to be on your game to watch out for balance issues.

      Ideally, get your power needs known up front, and buy the single largest battery you can to cover that - typically TWICE your calculated power budget, since one does not want to go past half way, or 50% DOD to get any sort of reasonable life out of your investment.

      I think the Powerwerx Supergate charger/ats to a *single* battery is your best investment at this point. (Or perhaps two 6V deep-cycle floodies in series, purchased and matched for dates at the same time) Solar can be added later after doing more reading.

      HINT - one of the biggest newbie mistakes in solar is not taking into account solar-insolation for your geographical location, in the winter months. Solar insolation is far different than the sunrise-to-sunset hours.

      The short form of it is, let's say you deplete your bank by 50 percent max. Will you have enough solar-insolation hours in the day to complete the recharging job in your intended timeframe, like a single day? If not, you will just be sulfating the batteries by not ever getting a full charge, and they will walk down in capacity and performance.

      Of course your grid-charger will take care of this - but wanted you to know this up front if you ever do go for long periods without ac.

      Comment


      • #4
        Originally posted by PNjunction View Post
        Don't make your Astron go bang, as it is not designed to be a battery charger. Oh, you'll get away with it *as long as the battery is NOT discharged too much*, but if it is, BANG. Usually guys don't find this out for years when they do a float on fully charged battery in the first place. First discharge and reapplication of AC - Pow.
        Easy fix for that, Yeah I learned the hard way 30 years ago.

        First thing is to use an Astron with variable voltage and current limit.I have a Astron VS-70M dedicated for the shack and 12 volt Stand-By battery. For the ole Power Lab 8, I have a 27 volt home brew I made not to long ago using my retired Astron VS-35M. I just re-wound the transformer, and changed out the feedback voltage divider. Works great and saved a lot of time and money buying a factory made 24 volt supply.

        When I changed out the 48 volt 16S 100 AH GBS batteries in my cart to 96 volt Leaf batteries I just coughed up the bucks for a Elcon PFC 2500. Wished they had them 40 years ago as it will charge effing everything from 36 to 400 volts in any algorithm you want. Even managed to get a programmer for it.
        MSEE, PE

        Comment


        • #5
          Thank you for your replies, guys.

          I was thinking that the power controller would protect the power supply. I guess that won't work. As for the power, I'll have to find something else.

          When I do drop the voltage on the battery, I unplug the Power supply and connect the battery charger until the battery gets to a better voltage. Whenever I am away, I connect the battery charger to let the battery build back up to the maximum voltage. The charger automatically stops charging when it is fully charged.

          I have learned that I can't move one back to the shed and expect it to charge on a permanent basis.

          The seller accepted my offer and has already shipped my charge controller. At least I have it when I get my panels.

          I used to build basic chargers by putting a diode in line with a power transformer. I am wondering if I could build one of them for the batteries.

          Comment


          • #6
            Originally posted by n4pgw View Post
            Thank you for your replies, guys.

            I was thinking that the power controller would protect the power supply. I guess that won't work. As for the power, I'll have to find something else.
            You are welcome, but I do not follow you. What do you mean by;" something else"?

            If you could raise your 13.8 VDC power supply to at least 16 volts, then you could play with the PWM controller to charge a battery. However if you could raise the voltage to 16 volts would also mean you could lower it to 13.2 to 13.6 volts to float the batteries and eliminate the fragile egg aka PWM controller all together. It is not needed nor would you want it if you understand what it does.

            Originally posted by n4pgw View Post
            When I do drop the voltage on the battery, I unplug the Power supply and connect the battery charger until the battery gets to a better voltage. Whenever I am away, I connect the battery charger to let the battery build back up to the maximum voltage. The charger automatically stops charging when it is fully charged.
            OK now we are getting to the root problem. You need to do some homework and learn the fundamentals of Pb battery charging because right now you do not even know the basics and leading you to wrong conclusions. Conclusions that will destroy your battery..

            Originally posted by n4pgw View Post
            I have learned that I can't move one back to the shed and expect it to charge on a permanent basis.
            Again this demonstrates you do not understand the basics

            Originally posted by n4pgw View Post
            I used to build basic chargers by putting a diode in line with a power transformer. I am wondering if I could build one of them for the batteries.
            No as there is more to it than you know as of now.

            Let's start with this, your 13.8 VDC power supply. What make and model is it? 90% chance this is all you need to do everything you want and all you need. It just requires an variable voltage so we can lower it a bit to match the battery requirements.

            There are 3 basic ways to charge a lead acid battery:

            1. Kind & Gentle. Provides maximum calendar and cycle life. It is using the Algorithm called FLOAT..

            2. Fast. Provides decent calendar and cycle life, and uses a fair bit of water. It uses the Algorithm called 3-Stage. The three stages are Bulk, Absorb & Float. There is that word float again. 3-Stage is what solar charge controllers try to do. Problem is there is not enough Sun Hours to complete if the batteries are cycled daily.

            3. Fast and Furious. As the name implies charge as fast as you can in as short of period of time as you can. Provides minimum calendar and cycle life if completed, and high water use. The algorithm is Constant Voltage which is the same as Absorb and Float. It is just uses a higher voltage to force the rectifier into Constant Current until you reach the set point voltage. The voltage is held until current tapers to virtually 0 amps.

            So which do you use? The one that fits the application. Solar users that cycle the battery everyday have to use either method 2 or 3, and if lightly cycled can use method 1. The problem with solar is two fold. Not enough Sun Hours to complete a full charge cycle and unknown intermittent power of a unreliable source.

            What do the pros use like utilities, commercial radio ops, communications faculties, telephone companies, 911, and military? They all use Float because they use batteries as Emergency Stand-By power. In prolonged outages they use Generators to keep the batteries charged up. The only down side to Float for consumers that use Consumer grade batteries is it can take up to 16 to 24 hours to fully saturate the batteries. The upside is the longest possible calendar and cycle life with minimum water use.

            Ho does float work. Real damn simple. It is a regulated DC power supply that tightly regulates voltage and limits charge current. Real simple to use. Set the voltage to the correct battery voltage for your battery type, and walk away. It never gets turned off. The DC power supply supplies all normal operating power and keeps the batteries at 100% waiting until needed. If power fails the batteries are already on-line and picks up the load. It is what all hams use if they know WTF they are doing, and what all critical mission pro users use. You already have what you need. You just do not know how to use it.
            MSEE, PE

            Comment


            • #7
              If you need to build a simple power supply with a couple diodes (CT) or bridge, a ferro resonant trans will give a better waveform
              and build in a fixed current limit. Trim the turns a bit for more accurate voltage, they largely regulate out line variations. For a fine
              cutoff, replace 2 diodes with SCRs.
              Now days buck regulators will give the max power at the voltage you chose, current limit is more difficult. I use them as a pre reg
              for a small drop linear reg, which handles transients and current limit. No need to rewind transformers any more. Bruce Roe

              Comment


              • #8
                Sorry to Hijack Thread, but I am also trying to do a similar project. I have a closet that contains 2 HD-SDI DVR's, 2 Comcast cable boxes, 3 ATSC modulators and about 24 SDI cameras, about 150 watt's. Our power lapses several times on some days and all these items have to reboot. some taking several min's. and the momentary loss of ATSC signal requires frequent reprogramming of some displays. I originally purchased a 15amp 24volt power supply to feed into a PWM or MPPT charge controller to control charge level output as well as LVD for attached loads. but from what I am reading in this post, I also have a 12V 30Amp adjustable power supply. This can be adjusted to my batteries float voltage and connected directly? 13.6 or 13.8 will float battery, maintain power to loads and the battery will catch lapses and maintaining critical equipment for moderate power outages? Learning here, so tell me what you know. Thanks in advance Jim...
                4X Suniva 250 watt, 8X t-105, OB Fx80, dc4812vrf

                Comment


                • #9
                  Charge controllers being fed from something other than solar PV panels, will perform "differently". Most PWM will fry internally ( a fuse or solid state device) MPPT may work for some time, but they will eventually misbehave too, from not being able to "track" a stiff supply instead of a PV.

                  So, your PS set to 13.7V IS actually a good way to float the batteries. You may need to tweak that voltage up a bit after you get some power cycles, to see what your setting for your loads and dropouts will actally be, 13.7 will not quickly recharge low batteries, takes several days, so if there are lots of dropouts, you need to up it a bit.
                  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 PNjunction View Post


                    Don't make your Astron go bang, as it is not designed to be a battery charger. Oh, you'll get away with it *as long as the battery is NOT discharged too much*, but if it is, BANG. Usually guys don't find this out for years when they do a float on fully charged battery in the first place. First discharge and reapplication of AC - Pow.
                    I have already blown fuses when the battery dropped too low for the power supply. I learned that when I use the battery, I leave the power supply attached to keep the voltage up. The Astron shows 13.8 volts, but the Inverter only reads 12.8 volts when I am using it with a load. Without a load, it reads 13.4 volts. When I disconnect the Astron while holding the load, the inverter voltage drops to 12.3 volts and stablizes there for a while.

                    Some of that has to be the voltage drop for the 10 feet of # 10 wire from the supply to the battery, and another 10 feet of the same wire from the battery to the inverter. Additionally, I don't know how accurate the volt meter on the inverter is, either.

                    Because I blew two fuses I tried using the smart charger, which is designed for deep cycle batteries. It is only 10 amps, but usually charges with lower current. When the battery is really low, it charges the battery without problems. But, it can't keep up with the load.

                    So, I connect the power supply when I am using the inverter under load. I switch back to the smart charger when I shut down and walk away.

                    Do NOT add batteries after the fact. In fact, paralleling even when new is something to avoid if you can, unless you want to spend some quality maintenance time figuring out why one is acting better / worse than the other. TWO of the same age/usage, manufacturer, capacity, build-date is about the best case, and even then, you have to be on your game to watch out for balance issues.
                    Buying the batteries all at once isn't in my plans. I know it isn't ideal, but I can't buy everything at once right now. I am starting small and growing it as I go.

                    As for the batteries, I plan to put each battery separately on a smart charger until all are up to their full level before connecting them all together. Since I have several different inverters, and I am adding a lot of DC lighting and other things in this area, I will probably end up with two or three smaller banks. One for my DC equipment, one for critical AC equipment and one for other AC equipment. In the event of an outage, I can switch battery banks as needed for the more critical services.

                    Also, at least one of the banks will be portable so I can use it for field work or for other areas of the house, if desired.

                    Then, again, my plans evolve a bit at the time as I get more pieces in and see how things work together.


                    Ideally, get your power needs known up front, and buy the single largest battery you can to cover that - typically TWICE your calculated power budget, since one does not want to go past half way, or 50% DOD to get any sort of reasonable life out of your investment.
                    LOL, I learned this lesson from experiment. When I let the battery drop to the point of failure, it was at 10.5 volts. Having had this experience, and having researched a bit, I decided that a deep discharge should be cut off no lower than 11.5 volts.



                    I think the Powerwerx Supergate charger/ats to a *single* battery is your best investment at this point. (Or perhaps two 6V deep-cycle floodies in series, purchased and matched for dates at the same time) Solar can be added later after doing more reading.
                    I looked into the Supergate and it looks like a great tool. I'll be

                    HINT - one of the biggest newbie mistakes in solar is not taking into account solar-insolation for your geographical location, in the winter months. Solar insolation is far different than the sunrise-to-sunset hours.

                    The short form of it is, let's say you deplete your bank by 50 percent max. Will you have enough solar-insolation hours in the day to complete the recharging job in your intended timeframe, like a single day? If not, you will just be sulfating the batteries by not ever getting a full charge, and they will walk down in capacity and performance.
                    I never heard of "solar insolation" before, but I did look into it. I realize that I won't ever get 100% from my solar system, or from my batteries. What I end up with in the end will depend a lot on results of my experimenting with it.

                    While I do believe that I can achieve enough alternative energy to feed this little segment of my house, I don't expect to be able to replace the power company with solar cells. Not without expecting a ten year return on investment.

                    It appears that my biggest investment is in the batteries and inverters, with the third biggest expense in the charging system. I am not anticipating miracles from the solar system these days. I did when I first started investigating this a few years ago, but some things actually dug into my brain.



                    Of course your grid-charger will take care of this - but wanted you to know this up front if you ever do go for long periods without ac.
                    That's why I want the grid charger. I am not expecting to take the house off the grid, but I can expect to back some of it up.

                    Comment


                    • #11
                      Originally posted by Sunking View Post
                      Your theory is wrong. To float charge a battery requires 13.8 volts, not 12.6 as 12.6 volts is an Open Circuit Voltage of a charged battery. If you have a 13.8 volt ham radio power supply, the PWM controller buys you nothing. The minimum foward voltage drop on a PWM controller is 1 volt. 13.8 - 1 = 12.8 volts. It takes a minimum 13.2 to 13.8 volt source depending on what alloy the Pb battery is. Quit geting your info from QRZ. Ideally you need a 18 volt source to charge a 12 volt battery. Solar panels are not voltage sources, they are current sources.

                      73's
                      I didn't get the info from QRZ. In fact it has been years since I visited. I do admit, though, I still have things to learn. which is why I am asking questions and experimenting.

                      Comment


                      • #12
                        Originally posted by Sunking View Post
                        "I was thinking that the power controller would protect the power supply. I guess that won't work. As for the power, I'll have to find something else." (N4PGW))

                        You are welcome, but I do not follow you. What do you mean by;" something else"?
                        I was planning on using the power supply and power controller to charge the battery bank. I was expecting that the power controller would protect the power supply from the battery in the event that the power fails. I have not experienced it, but I have been warned many times that a power supply connected directly to the 12 volt battery will burn out the power transistors if the ac power fails. Since the power controller will not protect the power supply from "Pow" I need to find a better source for charging the batteries.


                        If you could raise your 13.8 VDC power supply to at least 16 volts, then you could play with the PWM controller to charge a battery. However if you could raise the voltage to 16 volts would also mean you could lower it to 13.2 to 13.6 volts to float the batteries and eliminate the fragile egg aka PWM controller all together. It is not needed nor would you want it if you understand what it does.
                        I admit that I know little about the power controllers, which is why I purchased one, so I can experiment with it and learn.

                        I am a little confused as what you just said doesn't seem to fit what I have been reading.

                        Here is my understanding (right or wrong): MPPT controllers take any higher voltage (within their range) and reduce it to 12* volts so the current can be captured and used for charging the batteries or the load. If a panel produces 24 volts at 1 Amps, then it reduces it to 12 v @ 2Amps so all the power can be used to power the load or charge the batteries. 48V@1A=12V@4A, 100V@.1A = 12V@10A.

                        However, as I understand it, the PWM controller takes 12-14 volts @ 1Amp and passes it to the battery, but 20V@1Amp is converted to 12 Volts at 1Amp. so the extra power is lost somewhere.


                        However the PWM controller takes a narrow voltage range and passes it through to the battery so if the solar voltage is 12 volts, it passes 12 volts, but if the voltage is 15 volts, it does not pass any voltage to the battery at all. It only passes the 12.x - 13.x volts to charge the battery. Above or below that voltage is power wasted. It doesn't handle high voltage at all.

                        I expect my understanding to be flawed as I have only read this so far.



                        OK now we are getting to the root problem. You need to do some homework and learn the fundamentals of Pb battery charging because right now you do not even know the basics and leading you to wrong conclusions. Conclusions that will destroy your battery..



                        Again this demonstrates you do not understand the basics

                        No as there is more to it than you know as of now.

                        Let's start with this, your 13.8 VDC power supply. What make and model is it? 90% chance this is all you need to do everything you want and all you need. It just requires an variable voltage so we can lower it a bit to match the battery requirements.
                        I am connected to an Astron RS-35M for the moment. The power supply I intended to use when I move to the store room is a Triplite PR-25. Both are regulated power supplies and I have learned from both experience and here, that I'll get a "pow" if the power fails and comes back on with low batteries. I blew two fuses that were lower than the supply rated, so I started connecting my smart charger to the battery when it is not actually in use. It is an Exide smart charger that operates at 10,2, and 60 amps (60 for boost only.) It will not keep the voltage up when I am using the battery. It does charge the battery when I have the load removed which is why I swap chargers when I no longer use it.

                        It supposedly charges the battery to a full charge and then leaves a maintenance charge on it. You can see when the battery is charged that the device turns on and then off quickly when the charge is full. Even though it is a 10 amp charger, it only uses 10 amps when the battery is pretty low. Right now, what little I have on the battery pulls about 6-8 amps from my Astron, but sometimes, after prolonged use, the current goes up to 10 amps.

                        I have disconnected the battery for a while and then plugged it back into the Astron. When I do, I might see as much as 20-25 amps pulled from the supply and it slowly drops back to 8-10 amps if I am using it, or down to 1-2 amps if the load is turned off.

                        I am hoping to find a "charger" (not voltage regulated power supply) that can handle 25-30 amps to charge the battery bank I plan to assemble. Right now, I am having no luck.


                        There are 3 basic ways to charge a lead acid battery:

                        1. Kind & Gentle. Provides maximum calendar and cycle life. It is using the Algorithm called FLOAT..

                        2. Fast. Provides decent calendar and cycle life, and uses a fair bit of water. It uses the Algorithm called 3-Stage. The three stages are Bulk, Absorb & Float. There is that word float again. 3-Stage is what solar charge controllers try to do. Problem is there is not enough Sun Hours to complete if the batteries are cycled daily.

                        3. Fast and Furious. As the name implies charge as fast as you can in as short of period of time as you can. Provides minimum calendar and cycle life if completed, and high water use. The algorithm is Constant Voltage which is the same as Absorb and Float. It is just uses a higher voltage to force the rectifier into Constant Current until you reach the set point voltage. The voltage is held until current tapers to virtually 0 amps.
                        The smart charger uses #1, I am sure. The Astron uses #3.

                        Currently, I use the Astron when I am actually using the load. Right now, I am running my computer equipment and an LED light. According to my Kill-a-Watt, they are drawing 84 watts or 137 VA. The inverter shows 12.9v and the Astron is showing 6 Amps draw. Since they do not share the same wire going to the battery, I presently have no way of knowing how much current is being passed to the battery verses being passed to the inverter from the Astron. It may be that I am drawing a very minimal load from the battery.



                        So which do you use? The one that fits the application. Solar users that cycle the battery everyday have to use either method 2 or 3, and if lightly cycled can use method 1. The problem with solar is two fold. Not enough Sun Hours to complete a full charge cycle and unknown intermittent power of a unreliable source.
                        I am hoping the majority of my use will be method 1. I'll be connected to battery 100%, but I'll also be using grid to keep the batteries topped off even while I am using them. Does that make sense? It's more like I am building a UPS with total grid isolation from the output side.


                        Grid >---->Charger>-->Battery Bank >-->Inverter>-->Load

                        Assuming the load is less than the charge, it may electrically look like:
                        Grid >---->Charger>-->Inverter>-->Load



                        What do the pros use like utilities, commercial radio ops, communications faculties, telephone companies, 911, and military? They all use Float because they use batteries as Emergency Stand-By power. In prolonged outages they use Generators to keep the batteries charged up. The only down side to Float for consumers that use Consumer grade batteries is it can take up to 16 to 24 hours to fully saturate the batteries. The upside is the longest possible calendar and cycle life with minimum water use.

                        Ho does float work. Real damn simple. It is a regulated DC power supply that tightly regulates voltage and limits charge current. Real simple to use. Set the voltage to the correct battery voltage for your battery type, and walk away. It never gets turned off. The DC power supply supplies all normal operating power and keeps the batteries at 100% waiting until needed. If power fails the batteries are already on-line and picks up the load. It is what all hams use if they know WTF they are doing, and what all critical mission pro users use. You already have what you need. You just do not know how to use it.
                        My regulated power supplies are not designed to limit the current. This is my problem. The smart charger isn't capable of handling the load while I use it. So, it looks like I am in need of a different kind of charger. I may have to look into building a current limiting power supply if I can't find one.

                        Comment


                        • #13
                          You may want to look into the Samlex SEC series chargers / supplies. They are a bit different from their supply-only line.

                          http://www.samlexamerica.com/product...ry.aspx?cid=M3

                          You can change it from a 3-stage to 2-stage charger, and/or power supply if necessary. Unlike a common Samlex power supply, these are purpose built for situations like this, and much higher amperage if needed - as long as you don't blow out your wall socket. Fortunately, they aren't linear supplies.

                          One of which is when you leave a smart charger on a battery that has a decent load going, you may end up in an endless absorb holding the voltage high forever, which is not good. The Samlex will take care of that.

                          The voltages and modes of operation are changed by dip-switches, so it may not be suitable if you are constantly changing modes all the time and wearing out the dip switches. You also have to supply your own dc cabling. Specs are good and tight, yet the analog steam-gauges are handy enough for relative readings across the room.

                          The manuals are easily available online, so take a peek and see if it floats your boat.

                          Comment


                          • #14
                            Originally posted by n4pgw View Post

                            I was planning on using the power supply and power controller to charge the battery bank. I was expecting that the power controller would protect the power supply from the battery in the event that the power fails. I have not experienced it, but I have been warned many times that a power supply connected directly to the 12 volt battery will burn out the power transistors if the ac power fails. Since the power controller will not protect the power supply from "Pow" I need to find a better source for charging the batteries.
                            That can be true if you have a PS design without current regulation. Even a good ole astron can bee a problem but the fix is super easy by adding 1 resistor anyone with solder skills and can read a schematic can do. If you are a ham I sure hope you know how to solder.

                            Again ask: WHAT MAKE AND MODEL PS DO YOU HAVE????????????????????????????????

                            I can help you but you must answer the question


                            Originally posted by n4pgw View Post
                            I am a little confused as what you just said doesn't seem to fit what I have been reading.

                            Here is my understanding (right or wrong): MPPT controllers take any higher voltage (within their range) and reduce it to 12* volts so the current can be captured and used for charging the batteries or the load. If a panel produces 24 volts at 1 Amps, then it reduces it to 12 v @ 2Amps so all the power can be used to power the load or charge the batteries. 48V@1A=12V@4A, 100V@.1A = 12V@10A.

                            However, as I understand it, the PWM controller takes 12-14 volts @ 1Amp and passes it to the battery, but 20V@1Amp is converted to 12 Volts at 1Amp. so the extra power is lost somewhere.


                            However the PWM controller takes a narrow voltage range and passes it through to the battery so if the solar voltage is 12 volts, it passes 12 volts, but if the voltage is 15 volts, it does not pass any voltage to the battery at all. It only passes the 12.x - 13.x volts to charge the battery. Above or below that voltage is power wasted. It doesn't handle high voltage at all.

                            I expect my understanding to be flawed as I have only read this so far.
                            Yep it is flawed for sure. PWM can do that, but NOT MPPT. Solar panels are CURRENT SOURCES not VOLTAGE SOURCES like a Power Supply. MPPT controllers are Power Converters, PWM are voltage regulators. The reason a PWM controller will not work with your PS is because your PS voltage is too low.and close to the battery voltage. If you could get your PS voltage up to 17 volts, and the PWM controller Current ratingg equals or exceeds your power supply maximum current, you could use a PWM controller. But under no circumstances will a MPPT controller work correctly. You would still need to get the PS voltage up to 17 volts if you want to try and risk destroying the MPPT controller.
                            MSEE, PE

                            Comment


                            • #15
                              Originally posted by n4pgw View Post
                              I am connected to an Astron RS-35M for the moment.
                              I just caught this. No problem easy fix. Gotta eat dinner, back in a while with FIX.
                              MSEE, PE

                              Comment

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