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I am in need of a 21 volt switching power supply with at least 5 amp capacity

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    I am in need of a 21 volt switching power supply with at least 5 amp capacity

    I would be open to a 24 volt @ 5 amp switching power supply that can be adjusted down to 21 volts permanently and the over load protection is still functional and low voltage cutoff 15 volt or higher if necessary

    I would rather not have to use a buck converter to get the voltage that I need

    So is anyone else that has successfully modify one for a slight lower voltage had good results willing to share with me the safest way to accomplish this task

    I googled for a 21 volt switching power supply and did not find very much information for switching power supply for above 4 amps I want something more like 6 to 8 amps for the battery pack for my battery operated air compressor

    I would prefer a meanwell switching power supply if possible but would consider other brands if necessary if you have had good results
    Last edited by sam_sam_sam; 02-19-2023, 05:51 PM.
    9 PC LCD Monitor
    6 LCD Flat Screen TV
    30 Desk Top Switching Power Supply
    10 Battery Charger Switching Power Supply for Power Tool
    6 18v Lithium Battery Power Boards for Tool Battery Packs
    1 XBox 360 Switching Power Supply and M Board
    25 Servo Drives 220/460 3 Phase
    6 De-soldering Station Switching Power Supply 1 Power Supply
    1 Dell Mother Board
    15 Computer Power Supply
    1 HP Printer Supply & Control Board * lighting finished it *


    These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

    1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
    2 Hem Saw Computer Stack Board

    All of these had CAPs POOF
    All of the mosfet that are taken out by bad caps

    #2
    Re: I am in need of a 21 volt switching power supply with at least 5 amp capacity

    i think your going to have to try the 24v route

    Comment


      #3
      Re: I am in need of a 21 volt switching power supply with at least 5 amp capacity

      Use a 24V power supply and trim it down to 21V. Like Meanwell SPV-150-24 24V 6.25A output "adjustable 20-26.4V" $80 but not much stock.

      Otherwise I would just mod the feedback loop by adding a resistor to get the low adjustment lower. Most are 21.6V or around +/-10%.

      Comment


        #4
        Re: I am in need of a 21 volt switching power supply with at least 5 amp capacity

        Maybe a used El Cheapo variable bench PSU you find at a flea market would do the trick? No mods required on getting the right voltage. Here are some 24V linear PSU’s, these should be easy to mod with an LM723. I’ve got 2 of those at work. Another solution is 2 linear PSU’s in series.

        Comment


          #5
          Re: I am in need of a 21 volt switching power supply with at least 5 amp capacity

          Originally posted by redwire View Post
          Use a 24V power supply and trim it down to 21V. Like Meanwell SPV-150-24 24V 6.25A output "adjustable 20-26.4V" $80 but not much stock.

          Otherwise I would just mod the feedback loop by adding a resistor to get the low adjustment lower. Most are 21.6V or around +/-10%.
          Thanks for the information

          I have decided to go with this model instead

          https://www.jameco.com/z/LRS-350-24-...y_2219823.html

          I will also try modeling to get a voltage closer to 21.0 volts if I have to
          Last edited by sam_sam_sam; 02-20-2023, 06:50 AM.
          9 PC LCD Monitor
          6 LCD Flat Screen TV
          30 Desk Top Switching Power Supply
          10 Battery Charger Switching Power Supply for Power Tool
          6 18v Lithium Battery Power Boards for Tool Battery Packs
          1 XBox 360 Switching Power Supply and M Board
          25 Servo Drives 220/460 3 Phase
          6 De-soldering Station Switching Power Supply 1 Power Supply
          1 Dell Mother Board
          15 Computer Power Supply
          1 HP Printer Supply & Control Board * lighting finished it *


          These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

          1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
          2 Hem Saw Computer Stack Board

          All of these had CAPs POOF
          All of the mosfet that are taken out by bad caps

          Comment


            #6
            Re: I am in need of a 21 volt switching power supply with at least 5 amp capacity

            It looks like your standard TL431/opto circuit for regulating the voltage. The main complaint about LRS-350 is the noisy fan.
            If you post a clear pic of the underside of the board corner where the trimmer pot is, and the pot's value, can figure out which resistor to modify to get it down to 21V.

            Comment


              #7
              Re: I am in need of a 21 volt switching power supply with at least 5 amp capacity

              The switching power supply came in the mail today and I am a little disappointed with how they mounted the ic chips to the metal enclosure no wonder they had to use a higher speed fan to keep it cool I have another switching power supply that has better heat sinks in it and use a temperature controlled fan that I relocated the temperature sensor and mounted to the heat sink

              I going to use another enclosure for this switching power supply and use some ATX heat sinks that are much better because I have a meter that I also want to use on it as well

              On thing that did right was to have the rectifier assembly to the metal enclosure as well interesting that they thought of this

              I will post some pictures of this switching power supply when I get finished modifying it
              Last edited by sam_sam_sam; 02-25-2023, 01:39 AM.
              9 PC LCD Monitor
              6 LCD Flat Screen TV
              30 Desk Top Switching Power Supply
              10 Battery Charger Switching Power Supply for Power Tool
              6 18v Lithium Battery Power Boards for Tool Battery Packs
              1 XBox 360 Switching Power Supply and M Board
              25 Servo Drives 220/460 3 Phase
              6 De-soldering Station Switching Power Supply 1 Power Supply
              1 Dell Mother Board
              15 Computer Power Supply
              1 HP Printer Supply & Control Board * lighting finished it *


              These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

              1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
              2 Hem Saw Computer Stack Board

              All of these had CAPs POOF
              All of the mosfet that are taken out by bad caps

              Comment


                #8
                Re: I am in need of a 21 volt switching power supply with at least 5 amp capacity

                Originally posted by redwire View Post
                It looks like your standard TL431/opto circuit for regulating the voltage. The main complaint about LRS-350 is the noisy fan.
                If you post a clear pic of the underside of the board corner where the trimmer pot is, and the pot's value, can figure out which resistor to modify to get it down to 21V.
                I will post some pictures of later on today
                9 PC LCD Monitor
                6 LCD Flat Screen TV
                30 Desk Top Switching Power Supply
                10 Battery Charger Switching Power Supply for Power Tool
                6 18v Lithium Battery Power Boards for Tool Battery Packs
                1 XBox 360 Switching Power Supply and M Board
                25 Servo Drives 220/460 3 Phase
                6 De-soldering Station Switching Power Supply 1 Power Supply
                1 Dell Mother Board
                15 Computer Power Supply
                1 HP Printer Supply & Control Board * lighting finished it *


                These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

                1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
                2 Hem Saw Computer Stack Board

                All of these had CAPs POOF
                All of the mosfet that are taken out by bad caps

                Comment


                  #9
                  Re: I am in need of a 21 volt switching power supply with at least 5 amp capacity

                  Diodegonewild showed the internals of some of these.
                  You don't need another enclosure, just use shims to take up the gaps.
                  Best to keep the original enclosure- we don't need to make the RFI noise floor worse than it already is.

                  To lower the output voltage more than the trimpot allows, reduce the high side divider resistor. Or parallel another across it.
                  Use one between 10x and 20x higher than the value currently installed.
                  "pokemon go... to hell!"

                  EOL it...
                  Originally posted by shango066
                  All style and no substance.
                  Originally posted by smashstuff30
                  guilty,guilty,guilty,guilty!
                  guilty of being cheap-made!

                  Comment


                    #10
                    Re: I am in need of a 21 volt switching power supply with at least 5 amp capacity

                    Originally posted by sam_sam_sam View Post
                    I would be open to a 24 volt @ 5 amp switching power supply that can be adjusted down to 21 volts permanently and the over load protection is still functional and low voltage cutoff 15 volt or higher if necessary

                    I would rather not have to use a buck converter to get the voltage that I need

                    So is anyone else that has successfully modify one for a slight lower voltage had good results willing to share with me the safest way to accomplish this task

                    I googled for a 21 volt switching power supply and did not find very much information for switching power supply for above 4 amps I want something more like 6 to 8 amps for the battery pack for my battery operated air compressor

                    I would prefer a meanwell switching power supply if possible but would consider other brands if necessary if you have had good results
                    Firstly, it is possible to adjust the output voltage of a switching power supply within certain limits, but this should only be done if you have the necessary skills and knowledge to ensure that it is done safely and correctly. Any modifications you make to a power supply can affect its performance, stability, and safety.

                    If you are not experienced in electronics, it is recommended that you consult with a professional or seek advice from an online community that specializes in power supply modifications. You should also be aware that any modifications you make to a power supply may void its warranty.

                    Regarding your specific requirements, you mentioned that you are looking for a 24V, 5-8A switching power supply that can be adjusted down to 21V and has overload protection and low voltage cutoff. Meanwell is a reputable brand that produces a wide range of switching power supplies, and they have several models that meet your requirements.

                    For example, the Meanwell RSP-150-24 model is a 24V, 6.5A power supply that has an adjustable output voltage range of 21.6V to 28.8V. It also has built-in overload protection and overvoltage protection, but it does not have a low voltage cutoff feature. You may need to add an external circuit to provide low voltage cutoff.

                    Another option is the Meanwell HRP-600-24 model, which is a 24V, 25A power supply that has an adjustable output voltage range of 21.6V to 28.8V. It has built-in overload protection, overvoltage protection, and overcurrent protection. However, this model may be overkill for your application.

                    In summary, modifying a power supply requires technical expertise and caution. You may want to seek advice from a professional or an online community. Meanwell is a reputable brand that produces quality power supplies, and there are models that meet your requirements, such as the RSP-150-24 and HRP-600-24.

                    Comment


                      #11
                      Re: I am in need of a 21 volt switching power supply with at least 5 amp capacity

                      The one I bought can be brought down to 20.5 so it has no trouble adjusting to 21.5 which is what I was looking for

                      The issue have now is that when hooking up the BMS protection cable it was wired backwards from what it has on the charging circuit board and on the and on the board for the battery as well so I have to buy a couple more of them and redo it the correct way

                      I did not realize that the b1-b4 on the charger board was not the pin outs c1-c4
                      The mistake I made was that I did not check the pin connector first before I removed it from the battery pack

                      What it really is b1 is to c4 b2 is to c3 b3 is to c2 b4 is c1 really weird that it is completely backwards
                      Last edited by sam_sam_sam; 02-26-2023, 09:22 PM.
                      9 PC LCD Monitor
                      6 LCD Flat Screen TV
                      30 Desk Top Switching Power Supply
                      10 Battery Charger Switching Power Supply for Power Tool
                      6 18v Lithium Battery Power Boards for Tool Battery Packs
                      1 XBox 360 Switching Power Supply and M Board
                      25 Servo Drives 220/460 3 Phase
                      6 De-soldering Station Switching Power Supply 1 Power Supply
                      1 Dell Mother Board
                      15 Computer Power Supply
                      1 HP Printer Supply & Control Board * lighting finished it *


                      These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

                      1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
                      2 Hem Saw Computer Stack Board

                      All of these had CAPs POOF
                      All of the mosfet that are taken out by bad caps

                      Comment


                        #12
                        Re: I am in need of a 21 volt switching power supply with at least 5 amp capacity

                        Well there is a very small surface mount resistor that is from the negative side of the battery pack to either the thermistor or the ID terminal I have not completely figured this out yet but I have the charger working on the modified battery packs that I bought from Battery Hookup that I posted earlier I also bought a couple of new chargers this version is a little different from the first ones that I bought it still runs very warm and this is with the cover off the top of the circuit board the switching transformer is running at about 175’F the diode double pack mounted on a heat sink running around 170*F switching transistor mounted on a heat sink running around 180*F the output capacitor running around 140*F

                        I have to mount these two battery chargers in an enclosure with a temperature controlled fans to keep running cooler than it running now

                        I post some pictures of this setup when I have it neater than what I have it right now I am just in the testing phase of it right now

                        I have not decided weather or not to cut out the primary side of the switching power supply and use the switching power that I bought for this project to begin with but I probably will do it anyway
                        Last edited by sam_sam_sam; 03-04-2023, 10:12 PM.
                        9 PC LCD Monitor
                        6 LCD Flat Screen TV
                        30 Desk Top Switching Power Supply
                        10 Battery Charger Switching Power Supply for Power Tool
                        6 18v Lithium Battery Power Boards for Tool Battery Packs
                        1 XBox 360 Switching Power Supply and M Board
                        25 Servo Drives 220/460 3 Phase
                        6 De-soldering Station Switching Power Supply 1 Power Supply
                        1 Dell Mother Board
                        15 Computer Power Supply
                        1 HP Printer Supply & Control Board * lighting finished it *


                        These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

                        1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
                        2 Hem Saw Computer Stack Board

                        All of these had CAPs POOF
                        All of the mosfet that are taken out by bad caps

                        Comment


                          #13
                          Re: I am in need of a 21 volt switching power supply with at least 5 amp capacity

                          Well this battery charger has a timer and it just tripped so my plan is not going to work the way I had hoped so now I going to hook up some 30 amp BMS protection boards that I had bought for this project to begin with

                          The reason I going to use the ones I bought from Harbor Freight is because I would know when battery packs were finished charging but I will have come up with something else for that part
                          9 PC LCD Monitor
                          6 LCD Flat Screen TV
                          30 Desk Top Switching Power Supply
                          10 Battery Charger Switching Power Supply for Power Tool
                          6 18v Lithium Battery Power Boards for Tool Battery Packs
                          1 XBox 360 Switching Power Supply and M Board
                          25 Servo Drives 220/460 3 Phase
                          6 De-soldering Station Switching Power Supply 1 Power Supply
                          1 Dell Mother Board
                          15 Computer Power Supply
                          1 HP Printer Supply & Control Board * lighting finished it *


                          These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

                          1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
                          2 Hem Saw Computer Stack Board

                          All of these had CAPs POOF
                          All of the mosfet that are taken out by bad caps

                          Comment


                            #14
                            Re: I am in need of a 21 volt switching power supply with at least 5 amp capacity

                            Well I found a current meter/volt meter module that I an going to use on this project

                            https://www.ebay.com/itm/133727606583
                            9 PC LCD Monitor
                            6 LCD Flat Screen TV
                            30 Desk Top Switching Power Supply
                            10 Battery Charger Switching Power Supply for Power Tool
                            6 18v Lithium Battery Power Boards for Tool Battery Packs
                            1 XBox 360 Switching Power Supply and M Board
                            25 Servo Drives 220/460 3 Phase
                            6 De-soldering Station Switching Power Supply 1 Power Supply
                            1 Dell Mother Board
                            15 Computer Power Supply
                            1 HP Printer Supply & Control Board * lighting finished it *


                            These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

                            1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
                            2 Hem Saw Computer Stack Board

                            All of these had CAPs POOF
                            All of the mosfet that are taken out by bad caps

                            Comment


                              #15
                              Re: I am in need of a 21 volt switching power supply with at least 5 amp capacity

                              Well after 3 times resetting the charger it finally completely changed the very big battery pack
                              9 PC LCD Monitor
                              6 LCD Flat Screen TV
                              30 Desk Top Switching Power Supply
                              10 Battery Charger Switching Power Supply for Power Tool
                              6 18v Lithium Battery Power Boards for Tool Battery Packs
                              1 XBox 360 Switching Power Supply and M Board
                              25 Servo Drives 220/460 3 Phase
                              6 De-soldering Station Switching Power Supply 1 Power Supply
                              1 Dell Mother Board
                              15 Computer Power Supply
                              1 HP Printer Supply & Control Board * lighting finished it *


                              These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

                              1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
                              2 Hem Saw Computer Stack Board

                              All of these had CAPs POOF
                              All of the mosfet that are taken out by bad caps

                              Comment

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