Need help with Low voltage protection circuit

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  • flinx
    Senior Member
    • Aug 2010
    • 132
    • USA

    #21
    Re: Need help with Low voltage protection circuit

    One of my ideas was to use an off the shelf battery alarm. This circuit is similar to one I built a long time ago, but you can buy the alarm for a couple of dollars. It does not have a relay so I took the circuit and made my own board with a heavy duty 30 amp relay.


    this board is 1.56"x 2.68"x 1.25" not ideal.
    I have not ordered any boards made yet, but my test version does work.

    The issue is there is no hysteresis and the off and on voltages are almost the same.

    I Do not know enough to modify the circuit to get a 1 or 2 volt spread in the on off.

    That's why I decided to try the mosfet circuit.

    Through hole components are preferred as any one can make it.
    "...off the record, unnamed government sources
    alluded to unsubstantiated innuendos about
    alleged indiscretions and insinuated that they
    are rumored not to be without basis for further
    speculation..."

    Comment

    • eccerr0r
      Solder Sloth
      • Nov 2012
      • 8665
      • USA

      #22
      Re: Need help with Low voltage protection circuit

      The problem is there is no generic solution unless you make a really complicated circuit. Hence you need a problem for this solution, you can't make a solution searching for a problem.

      So we need a problem that a solution needs to be found. Right now it seems you only have an academic problem, and all we can give is an academic solution.

      Comment

      • sam_sam_sam
        Badcaps Legend
        • Jul 2011
        • 6023
        • USA

        #23
        Re: Need help with Low voltage protection circuit

        If you were making a battery pack there are BMS balancing protection board out there that can handle up to 100 amps the can be little bit big but the 40 amp version are some what smaller

        I understand your problem because I have a 24 volt soldering iron that I want a 24 battery pack to build but the products out on the market for soldering iron did NOT work correctly which I was very disappointed with the the results

        Granted I did not spend very much money for BMS balancing protection board
        The problem with the BMS balancing protection board that were recommended did NOT keep the batteries balanced like advertised so results were terrible

        Then the same company has a new version of the battery operated soldering iron the results of this board is a lot better but the cost was a lot more money because the quality of battery were not was advertised but when I get some time I will put together a name brand batteries and have a google working unit

        I would recommend that you build a battery pack with a good quality BMS balancing protection board and just use a cord to the outside and use it that

        This is what I have done for my soldering iron the battery pack and the charger unit I posted earlier is what I did so I could use the soldering iron on battery power

        But with setup I can power what ever I want because what I used which I did not post was a USB power bank that uses the battery pack which I modify for this purpose so yes I did spend some money on this setup but I could use for many different devices and when I was doing this modification I had this in mind


        Now if you are only want to use 20 volt instead of 24 volts I have a setup you can do which has all the parts you need to do it

        The battery pack

        The charger
        ( for the version I want to make I going to see how they are doing the charging circuit to see if I can modify it or not

        The USB port unit

        One note I am going to make a 12 volt version of the same thing that I am talking about

        I going to make a power supply for some LED modules that I going to use with a 18 volt solar panels that I have

        If you are interested on how to do this just let me know and I go into some details on how you do the modification
        Last edited by sam_sam_sam; 08-16-2020, 03:57 PM.

        Comment

        • flinx
          Senior Member
          • Aug 2010
          • 132
          • USA

          #24
          Re: Need help with Low voltage protection circuit

          Do the BMS work without the balancing circuits connected? if so I could just use that.

          I do not want to build battery packs if I do not need to.
          "...off the record, unnamed government sources
          alluded to unsubstantiated innuendos about
          alleged indiscretions and insinuated that they
          are rumored not to be without basis for further
          speculation..."

          Comment

          • sam_sam_sam
            Badcaps Legend
            • Jul 2011
            • 6023
            • USA

            #25
            Re: Need help with Low voltage protection circuit

            Originally posted by flinx
            Do the BMS work without the balancing circuits connected? if so I could just use that.

            I do not want to build battery packs if I do not need to.
            You can just buy protection board and for the most part they work however the problem you can run into is if your batteries are not balanced your running time can greatly lower

            You can somewhat overcome this problem with a battery tester that tell you what the milliamperes hours each battery that is tested but you have to do a little bit more work up front

            Now with a BMS balancing protection board the balancing of batteries is even more important than just using just a protection board only
            with this BMS board you have one step you must follow and that you have to make sure that your discharge roll off voltages are very close to each other as well as milliamperes hours

            You have use a special battery tester for doing this type of testing

            One note the battery pack that I have mentioned earlier you can get very good results from them they do use brand name batteries other wise I would not have recommend them there battery protection board or if it has the BMS balancing function on them works pretty good from what I have seen ( the run time results are what I would expect from the type of batteries used

            Yes I do take these battery packs apart to see what batteries are used
            Last edited by sam_sam_sam; 08-16-2020, 04:19 PM.

            Comment

            • flinx
              Senior Member
              • Aug 2010
              • 132
              • USA

              #26
              Re: Need help with Low voltage protection circuit

              Originally posted by eccerr0r
              The problem is there is no generic solution unless you make a really complicated circuit. Hence you need a problem for this solution, you can't make a solution searching for a problem.

              So we need a problem that a solution needs to be found. Right now it seems you only have an academic problem, and all we can give is an academic solution.
              I appreciate your input.
              "...off the record, unnamed government sources
              alluded to unsubstantiated innuendos about
              alleged indiscretions and insinuated that they
              are rumored not to be without basis for further
              speculation..."

              Comment

              • budm
                Badcaps Legend
                • Feb 2010
                • 40746
                • USA

                #27
                Re: Need help with Low voltage protection circuit

                http://liionbms.com/php/wp_lovtg_cutoff.php
                You cannot find 5S, 6S BMS 20A, 30A, 40A with or without Balancer?
                Motor will have high in-rush current to keep that in mind also.
                Vacuum is just one type of load.
                Last edited by budm; 08-16-2020, 04:26 PM.
                Never stop learning
                Basic LCD TV and Monitor troubleshooting guides.
                http://www.badcaps.net/forum/showthr...956#post305956

                Voltage Regulator (LDO) testing:
                http://www.badcaps.net/forum/showthr...999#post300999

                Inverter testing using old CFL:
                http://www.badcaps.net/forum/showthr...er+testing+cfl

                Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                http://s807.photobucket.com/user/budm/library/

                TV Factory reset codes listing:
                http://www.badcaps.net/forum/showthread.php?t=24809

                Comment

                • sam_sam_sam
                  Badcaps Legend
                  • Jul 2011
                  • 6023
                  • USA

                  #28
                  Re: Need help with Low voltage protection circuit

                  Originally posted by budm
                  http://liionbms.com/php/wp_lovtg_cutoff.php
                  You cannot find 5S, 6S BMS 20A, 30A, 40A with or without Balancer?
                  Motor will have high in-rush current to keep that in mind also.
                  Thanks for posting this I will read it more details later

                  Comment

                  • budm
                    Badcaps Legend
                    • Feb 2010
                    • 40746
                    • USA

                    #29
                    Re: Need help with Low voltage protection circuit

                    Do you have the schematic in your post 21?
                    Never stop learning
                    Basic LCD TV and Monitor troubleshooting guides.
                    http://www.badcaps.net/forum/showthr...956#post305956

                    Voltage Regulator (LDO) testing:
                    http://www.badcaps.net/forum/showthr...999#post300999

                    Inverter testing using old CFL:
                    http://www.badcaps.net/forum/showthr...er+testing+cfl

                    Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                    http://s807.photobucket.com/user/budm/library/

                    TV Factory reset codes listing:
                    http://www.badcaps.net/forum/showthread.php?t=24809

                    Comment

                    • budm
                      Badcaps Legend
                      • Feb 2010
                      • 40746
                      • USA

                      #30
                      Re: Need help with Low voltage protection circuit

                      Originally posted by sam_sam_sam
                      Thanks for posting this I will read it more details later
                      I just start playing with the BMS after reading some of your threads.
                      I bought 1s, 2s, 3s, 4s BMS with and without balancer (not apply to 1s of course).
                      What I found is that the one without Balancer will stop charging when one cell of the series cell Voltage reaches 4.2V first but another do not then it stop charging, so other cell are not fully charged.
                      Never stop learning
                      Basic LCD TV and Monitor troubleshooting guides.
                      http://www.badcaps.net/forum/showthr...956#post305956

                      Voltage Regulator (LDO) testing:
                      http://www.badcaps.net/forum/showthr...999#post300999

                      Inverter testing using old CFL:
                      http://www.badcaps.net/forum/showthr...er+testing+cfl

                      Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                      http://s807.photobucket.com/user/budm/library/

                      TV Factory reset codes listing:
                      http://www.badcaps.net/forum/showthread.php?t=24809

                      Comment

                      • flinx
                        Senior Member
                        • Aug 2010
                        • 132
                        • USA

                        #31
                        Re: Need help with Low voltage protection circuit

                        Originally posted by budm
                        Do you have the schematic in your post 21?
                        not as such, I basically copied it from a physical specimen directly in to the easyeda program. I skipped making an actual schematic. I have not triple checked that it is correct.
                        "...off the record, unnamed government sources
                        alluded to unsubstantiated innuendos about
                        alleged indiscretions and insinuated that they
                        are rumored not to be without basis for further
                        speculation..."

                        Comment

                        • sam_sam_sam
                          Badcaps Legend
                          • Jul 2011
                          • 6023
                          • USA

                          #32
                          Re: Need help with Low voltage protection circuit

                          Originally posted by budm
                          I just start playing with the BMS after reading some of your threads.
                          I bought 1s, 2s, 3s, 4s BMS with and without balancer (not apply to 1s of course).
                          What I found is that the one without Balancer will stop charging when one cell of the series cell Voltage reaches 4.2V first but another do not then it stop charging, so other cell are not fully charged.
                          Some BMS balancing protection boards are very touchy in that if your gets close to voltage cutoff the charging current drops off considerably which if you do have a way to test batteries in the way I was talking about earlier you might be better off using just a regular protection board


                          This is the problem with protection board in general this is why it is important to get the batteries that are going to be used with the same voltage roll off —>voltage and milliamperes hour results are as close as possible to get this best results for charging and discharging cycle

                          Now if you are using new batteries this not as much of a problem as if you are using used batteries
                          Last edited by sam_sam_sam; 08-16-2020, 05:35 PM.

                          Comment

                          • budm
                            Badcaps Legend
                            • Feb 2010
                            • 40746
                            • USA

                            #33
                            Re: Need help with Low voltage protection circuit

                            Originally posted by sam_sam_sam
                            Some BMS balancing protection boards are very touchy in that if your gets close to voltage cutoff the charging current drops off considerably which if you do have a way to test batteries in the way I was talking about earlier you might be better off using just a regular protection board


                            This is the problem with protection board in general this is why it is important to get the batteries that are going to be used the voltage roll off —>voltage and milliamperes hour results are as close as possible to get this best results for charging and discharging cycle

                            Now if you are using new batteries this not as much of a problem as if you are using used batteries
                            That is why I ask about the battery tester and you recommended one for me but I do not have the money right now to buy one.
                            Never stop learning
                            Basic LCD TV and Monitor troubleshooting guides.
                            http://www.badcaps.net/forum/showthr...956#post305956

                            Voltage Regulator (LDO) testing:
                            http://www.badcaps.net/forum/showthr...999#post300999

                            Inverter testing using old CFL:
                            http://www.badcaps.net/forum/showthr...er+testing+cfl

                            Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                            http://s807.photobucket.com/user/budm/library/

                            TV Factory reset codes listing:
                            http://www.badcaps.net/forum/showthread.php?t=24809

                            Comment

                            • budm
                              Badcaps Legend
                              • Feb 2010
                              • 40746
                              • USA

                              #34
                              Re: Need help with Low voltage protection circuit

                              Originally posted by flinx
                              not as such, I basically copied it from a physical specimen directly in to the easyeda program. I skipped making an actual schematic. I have not triple checked that it is correct.
                              If I see the schematic then I may be able to tell you where to add resistor for the Hysteresis.
                              Never stop learning
                              Basic LCD TV and Monitor troubleshooting guides.
                              http://www.badcaps.net/forum/showthr...956#post305956

                              Voltage Regulator (LDO) testing:
                              http://www.badcaps.net/forum/showthr...999#post300999

                              Inverter testing using old CFL:
                              http://www.badcaps.net/forum/showthr...er+testing+cfl

                              Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                              http://s807.photobucket.com/user/budm/library/

                              TV Factory reset codes listing:
                              http://www.badcaps.net/forum/showthread.php?t=24809

                              Comment

                              • sam_sam_sam
                                Badcaps Legend
                                • Jul 2011
                                • 6023
                                • USA

                                #35
                                Re: Need help with Low voltage protection circuit

                                Originally posted by budm
                                That is why I ask about the battery tester and you recommended one for me but I do not have the money right now to buy one.
                                I know it is a little bit price-e I just happened to have bonus money when I bought the first one and I really did not think that it would make that much difference using this type of battery testing device to put battery packs together but it does make a difference

                                Because I was just using a IMAX B6 version 2 before I bought the battery tester I was talking about earlier
                                You could do this way and have milliamperes results with this device which solve half of the problem

                                Now to get the voltages roll off is not so easy but if you are watching the discharge cycle when it to where the current start dropping off quickly and note the milliamperes hours reading and the amount of elapsed time results at this point you kind-a do the same thing about the voltage roll cutoff reading one note this approach is not quite as accurate but it could be doable but if you have the patience to do it me personally I do not have this much patience for this when you are testing high milliamperes hours batteries

                                Because what makes it difficult to get the voltage roll off with this device is that with this device it maintains the voltage output at a set point of 3.2 volts and drop the current output and when the current output is about 10 amps it stops

                                Let say that you set the amperage for one amp and are watching the display and you see the amperage drop to 900 milliampere this would be your voltages drop off starts but you would not have what the curve would be but this would give more information than if you just set the device and just read the results when the device is done with the discharge cycle you would also want to look at the charging current roll off as well because some time they are different milliamperes hours and elapsed time

                                One thought before I saw this battery tester that I have now

                                Was to take a micro controller and plot the time it takes for the voltage to drop from 900 milliamperes to when it gets to 500 milliamperes because below this value the voltage drop very quickly any way

                                I hope that this information will help you
                                Last edited by sam_sam_sam; 08-16-2020, 06:17 PM.

                                Comment

                                • eccerr0r
                                  Solder Sloth
                                  • Nov 2012
                                  • 8665
                                  • USA

                                  #36
                                  Re: Need help with Low voltage protection circuit

                                  Post 21 circuit will eventually fail at 20V with a 12V relay due to power dissipation of the relay. A 24V relay would be marginal.

                                  Horrible design, granted it was a trivial reverse engineer.
                                  Attached Files

                                  Comment

                                  • flinx
                                    Senior Member
                                    • Aug 2010
                                    • 132
                                    • USA

                                    #37
                                    Re: Need help with Low voltage protection circuit

                                    Originally posted by budm
                                    If I see the schematic then I may be able to tell you where to add resistor for the Hysteresis.
                                    ok I whipped this up


                                    a relay can be subbed for the buzzer.
                                    Last edited by flinx; 08-16-2020, 07:34 PM.
                                    "...off the record, unnamed government sources
                                    alluded to unsubstantiated innuendos about
                                    alleged indiscretions and insinuated that they
                                    are rumored not to be without basis for further
                                    speculation..."

                                    Comment

                                    • flinx
                                      Senior Member
                                      • Aug 2010
                                      • 132
                                      • USA

                                      #38
                                      Re: Need help with Low voltage protection circuit

                                      Originally posted by eccerr0r
                                      Post 21 circuit will eventually fail at 20V with a 12V relay due to power dissipation of the relay. A 24V relay would be marginal.

                                      Horrible design, granted it was a trivial reverse engineer.
                                      edit: what's horrible?
                                      Last edited by flinx; 08-16-2020, 07:42 PM.
                                      "...off the record, unnamed government sources
                                      alluded to unsubstantiated innuendos about
                                      alleged indiscretions and insinuated that they
                                      are rumored not to be without basis for further
                                      speculation..."

                                      Comment

                                      • eccerr0r
                                        Solder Sloth
                                        • Nov 2012
                                        • 8665
                                        • USA

                                        #39
                                        Re: Need help with Low voltage protection circuit

                                        Depends on the specific relay you use and the mechanical variation between units to tell what voltage it will engage at. I have a few 24 V relays that are worthless at 12V, they will not pull at all.

                                        The idea of hysteresis is to provide some feedback from pin 1 to pin 3 of the IC with a resistor, however you will need to add a resistor between the zener and pin 3 of the IC because it would otherwise have no way to increase the threshold. Looking at this, you will likely need to use the other amplifier in the LM358 to provide more consistent triggering, mostly because the voltage output of the LM358 will depend on the setpoint...

                                        Modifying for MOSFET use, you will need to be careful of going near the VGSmax limit of the device. It's actually fairly trivial but the key component is that LM358, without it you will not get the gain needed for reliable on/off.

                                        The full Li-ion battery protection (charge and discharge, as well as balancing) I designed using LM358s and LM324s ended up drawing a considerable amount of current and thus unacceptable for real implementations. However it does do the function needed, though I did design for 4S. I suspect modding for 5S won't be too hard but will require more amplifiers - luckily LM358/LM324s can go 30V+ single ended. In commercial designs they will not be using LM358s and LM324s because they eat too much power, along with the voltage references (discrete zeners need to be carefully designed between noise and power consumption.)
                                        Last edited by eccerr0r; 08-16-2020, 08:00 PM.

                                        Comment

                                        • budm
                                          Badcaps Legend
                                          • Feb 2010
                                          • 40746
                                          • USA

                                          #40
                                          Re: Need help with Low voltage protection circuit

                                          "The idea of hysteresis is to provide some feedback from pin 1 to pin 3 of the IC with a resistor, however you will need to add a resistor between the zener and pin 3 of the IC because it would otherwise have no way to increase the threshold. Looking at this, you will likely need to use the other amplifier in the LM358 to provide more consistent triggering, mostly because the voltage output of the LM358 will depend on the setpoint.."

                                          +1

                                          OP: your circuit looks to be from here: https://www.instructables.com/id/BATTERY-LOW-ALARM/

                                          BTW, using compactor IC such as LM393 with open Collector output is more suitable than using OPAMP.
                                          You can also look into MAX6457 but it is SMD.
                                          Last edited by budm; 08-16-2020, 08:06 PM.
                                          Never stop learning
                                          Basic LCD TV and Monitor troubleshooting guides.
                                          http://www.badcaps.net/forum/showthr...956#post305956

                                          Voltage Regulator (LDO) testing:
                                          http://www.badcaps.net/forum/showthr...999#post300999

                                          Inverter testing using old CFL:
                                          http://www.badcaps.net/forum/showthr...er+testing+cfl

                                          Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                                          http://s807.photobucket.com/user/budm/library/

                                          TV Factory reset codes listing:
                                          http://www.badcaps.net/forum/showthread.php?t=24809

                                          Comment

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