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12V lead acid charger with LM317 not charging


Need help with LM317 voltage regulator circuitLM317 Constant Current Battery Charger Questioncharging a lead acid battery bank with a 19v laptop chargerHow to make 5v DC UPS Circuit?LM317 output voltage to 0 V with transformerless negative voltage created through a buck converterLM317 Sealed lead acid chargerCurrent booster with LM317 not working properly in LTspice simulation?Power supply beginner errorLead acid chargingCharge a 12V marine/boat battery with AC






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3












$begingroup$


I have this circuit built and tested. I think this should work and charge the battery with 0.4A to about 13.5V.



The Problem: it doesn't charge and between U1 and U3 (Battery) is a current of about 0.03A, but why?



The LM2596 is a Buck converter Breakout board and that works flawlessly.
R1 is a 4W resistor so that won't be the problem



Why doesn't it charge?





schematic





simulate this circuit – Schematic created using CircuitLab










share|improve this question











$endgroup$









  • 4




    $begingroup$
    Why do you put the Buck converter in between? Just to get rid of that one volt?
    $endgroup$
    – jusaca
    Aug 7 at 11:23

















3












$begingroup$


I have this circuit built and tested. I think this should work and charge the battery with 0.4A to about 13.5V.



The Problem: it doesn't charge and between U1 and U3 (Battery) is a current of about 0.03A, but why?



The LM2596 is a Buck converter Breakout board and that works flawlessly.
R1 is a 4W resistor so that won't be the problem



Why doesn't it charge?





schematic





simulate this circuit – Schematic created using CircuitLab










share|improve this question











$endgroup$









  • 4




    $begingroup$
    Why do you put the Buck converter in between? Just to get rid of that one volt?
    $endgroup$
    – jusaca
    Aug 7 at 11:23













3












3








3


1



$begingroup$


I have this circuit built and tested. I think this should work and charge the battery with 0.4A to about 13.5V.



The Problem: it doesn't charge and between U1 and U3 (Battery) is a current of about 0.03A, but why?



The LM2596 is a Buck converter Breakout board and that works flawlessly.
R1 is a 4W resistor so that won't be the problem



Why doesn't it charge?





schematic





simulate this circuit – Schematic created using CircuitLab










share|improve this question











$endgroup$




I have this circuit built and tested. I think this should work and charge the battery with 0.4A to about 13.5V.



The Problem: it doesn't charge and between U1 and U3 (Battery) is a current of about 0.03A, but why?



The LM2596 is a Buck converter Breakout board and that works flawlessly.
R1 is a 4W resistor so that won't be the problem



Why doesn't it charge?





schematic





simulate this circuit – Schematic created using CircuitLab







12v lm317 lead






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited Aug 7 at 11:17









brhans

10.2k2 gold badges24 silver badges32 bronze badges




10.2k2 gold badges24 silver badges32 bronze badges










asked Aug 7 at 11:13









Mark OEMark OE

243 bronze badges




243 bronze badges










  • 4




    $begingroup$
    Why do you put the Buck converter in between? Just to get rid of that one volt?
    $endgroup$
    – jusaca
    Aug 7 at 11:23












  • 4




    $begingroup$
    Why do you put the Buck converter in between? Just to get rid of that one volt?
    $endgroup$
    – jusaca
    Aug 7 at 11:23







4




4




$begingroup$
Why do you put the Buck converter in between? Just to get rid of that one volt?
$endgroup$
– jusaca
Aug 7 at 11:23




$begingroup$
Why do you put the Buck converter in between? Just to get rid of that one volt?
$endgroup$
– jusaca
Aug 7 at 11:23










4 Answers
4






active

oldest

votes


















10












$begingroup$

Read the datasheet of the LM317, on page 9 it states:



enter image description here



So when you feed the LM317 14 V it can regulate to 11 V and lower, not 13.5 V.



Also there will be 1.25 V across R1 so for 13.5 V you will need to put at least 13.5 + 1.25 + 3 = 17.75 V into the LM317.



The ~15 V you're feeding the LM2596 board isn't even enough, there's no need to have that LM2596 converter in place so remove it.



You will need a power source with a higher voltage than ~ 15 V.



As the LM317 will drop 3 V or more at a significant current, it will get hot so use a heatsink! If the LM317 gets too hot it lowers the current to lower its power dissipation (and allow it to cool down).



Note that your circuit does not have a well defined "stop charging" voltage, current will keep flowing and your battery might over charge!



I have built an LM317 based battery charger for my 12 V car battery. I use a 19 V laptop power supply I had lying around to power it. In that design I do not use the LM317 as a current source, instead I use it as a voltage regulator set to 13.5 V. Then when the battery has a lower voltage, the LM317 will hit its build-in current limit (< 2.2 A). For a car battery 2.2 A or less is fine. As the battery charges an the voltage reaches 13.5 V, the current gets smaller and smaller until only a leakage current is left.



If that 2.2 A is too much for your battery, use this circuit instead:



enter image description here






share|improve this answer











$endgroup$






















    4












    $begingroup$

    You need more than 14V at input if you want to charge a battery to 13.5V. About 18V should be enough. LM317 needs about 3V between Vin and Vout to work. And there will be 1.25V between Vout and Adj. And then the battery will have 13.5V. 13.5+1.25V+3V is 17.75V.






    share|improve this answer











    $endgroup$






















      3












      $begingroup$

      The problem you have is caused by the LM317 and the voltage you have available to it.



      The LM317 requires a difference of 3V between the input and output voltage. You have 15V from your powersupply (which you drop to 14 with the LM2596.) That's only 1.5V above the output voltage (13.5V) that you need for the battery.



      You really only have two choices:



      1. Use a higher input voltage (at least 17V)

      2. Use a different current regulator that can work with the available voltage.

      In any case, the LM2596 is only making things worse.






      share|improve this answer









      $endgroup$






















        0












        $begingroup$

        Also, if the power supply is switched off and the 12V battery is still attached, there's a negative voltage difference (Vin-Vout) on the LM317, a situation not mentioned in the data sheet as far as I can see. If that causes a leak current, it would drain the battery.






        share|improve this answer









        $endgroup$

















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          4 Answers
          4






          active

          oldest

          votes








          4 Answers
          4






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes









          10












          $begingroup$

          Read the datasheet of the LM317, on page 9 it states:



          enter image description here



          So when you feed the LM317 14 V it can regulate to 11 V and lower, not 13.5 V.



          Also there will be 1.25 V across R1 so for 13.5 V you will need to put at least 13.5 + 1.25 + 3 = 17.75 V into the LM317.



          The ~15 V you're feeding the LM2596 board isn't even enough, there's no need to have that LM2596 converter in place so remove it.



          You will need a power source with a higher voltage than ~ 15 V.



          As the LM317 will drop 3 V or more at a significant current, it will get hot so use a heatsink! If the LM317 gets too hot it lowers the current to lower its power dissipation (and allow it to cool down).



          Note that your circuit does not have a well defined "stop charging" voltage, current will keep flowing and your battery might over charge!



          I have built an LM317 based battery charger for my 12 V car battery. I use a 19 V laptop power supply I had lying around to power it. In that design I do not use the LM317 as a current source, instead I use it as a voltage regulator set to 13.5 V. Then when the battery has a lower voltage, the LM317 will hit its build-in current limit (< 2.2 A). For a car battery 2.2 A or less is fine. As the battery charges an the voltage reaches 13.5 V, the current gets smaller and smaller until only a leakage current is left.



          If that 2.2 A is too much for your battery, use this circuit instead:



          enter image description here






          share|improve this answer











          $endgroup$



















            10












            $begingroup$

            Read the datasheet of the LM317, on page 9 it states:



            enter image description here



            So when you feed the LM317 14 V it can regulate to 11 V and lower, not 13.5 V.



            Also there will be 1.25 V across R1 so for 13.5 V you will need to put at least 13.5 + 1.25 + 3 = 17.75 V into the LM317.



            The ~15 V you're feeding the LM2596 board isn't even enough, there's no need to have that LM2596 converter in place so remove it.



            You will need a power source with a higher voltage than ~ 15 V.



            As the LM317 will drop 3 V or more at a significant current, it will get hot so use a heatsink! If the LM317 gets too hot it lowers the current to lower its power dissipation (and allow it to cool down).



            Note that your circuit does not have a well defined "stop charging" voltage, current will keep flowing and your battery might over charge!



            I have built an LM317 based battery charger for my 12 V car battery. I use a 19 V laptop power supply I had lying around to power it. In that design I do not use the LM317 as a current source, instead I use it as a voltage regulator set to 13.5 V. Then when the battery has a lower voltage, the LM317 will hit its build-in current limit (< 2.2 A). For a car battery 2.2 A or less is fine. As the battery charges an the voltage reaches 13.5 V, the current gets smaller and smaller until only a leakage current is left.



            If that 2.2 A is too much for your battery, use this circuit instead:



            enter image description here






            share|improve this answer











            $endgroup$

















              10












              10








              10





              $begingroup$

              Read the datasheet of the LM317, on page 9 it states:



              enter image description here



              So when you feed the LM317 14 V it can regulate to 11 V and lower, not 13.5 V.



              Also there will be 1.25 V across R1 so for 13.5 V you will need to put at least 13.5 + 1.25 + 3 = 17.75 V into the LM317.



              The ~15 V you're feeding the LM2596 board isn't even enough, there's no need to have that LM2596 converter in place so remove it.



              You will need a power source with a higher voltage than ~ 15 V.



              As the LM317 will drop 3 V or more at a significant current, it will get hot so use a heatsink! If the LM317 gets too hot it lowers the current to lower its power dissipation (and allow it to cool down).



              Note that your circuit does not have a well defined "stop charging" voltage, current will keep flowing and your battery might over charge!



              I have built an LM317 based battery charger for my 12 V car battery. I use a 19 V laptop power supply I had lying around to power it. In that design I do not use the LM317 as a current source, instead I use it as a voltage regulator set to 13.5 V. Then when the battery has a lower voltage, the LM317 will hit its build-in current limit (< 2.2 A). For a car battery 2.2 A or less is fine. As the battery charges an the voltage reaches 13.5 V, the current gets smaller and smaller until only a leakage current is left.



              If that 2.2 A is too much for your battery, use this circuit instead:



              enter image description here






              share|improve this answer











              $endgroup$



              Read the datasheet of the LM317, on page 9 it states:



              enter image description here



              So when you feed the LM317 14 V it can regulate to 11 V and lower, not 13.5 V.



              Also there will be 1.25 V across R1 so for 13.5 V you will need to put at least 13.5 + 1.25 + 3 = 17.75 V into the LM317.



              The ~15 V you're feeding the LM2596 board isn't even enough, there's no need to have that LM2596 converter in place so remove it.



              You will need a power source with a higher voltage than ~ 15 V.



              As the LM317 will drop 3 V or more at a significant current, it will get hot so use a heatsink! If the LM317 gets too hot it lowers the current to lower its power dissipation (and allow it to cool down).



              Note that your circuit does not have a well defined "stop charging" voltage, current will keep flowing and your battery might over charge!



              I have built an LM317 based battery charger for my 12 V car battery. I use a 19 V laptop power supply I had lying around to power it. In that design I do not use the LM317 as a current source, instead I use it as a voltage regulator set to 13.5 V. Then when the battery has a lower voltage, the LM317 will hit its build-in current limit (< 2.2 A). For a car battery 2.2 A or less is fine. As the battery charges an the voltage reaches 13.5 V, the current gets smaller and smaller until only a leakage current is left.



              If that 2.2 A is too much for your battery, use this circuit instead:



              enter image description here







              share|improve this answer














              share|improve this answer



              share|improve this answer








              edited Aug 7 at 11:39

























              answered Aug 7 at 11:25









              BimpelrekkieBimpelrekkie

              56.8k2 gold badges55 silver badges130 bronze badges




              56.8k2 gold badges55 silver badges130 bronze badges


























                  4












                  $begingroup$

                  You need more than 14V at input if you want to charge a battery to 13.5V. About 18V should be enough. LM317 needs about 3V between Vin and Vout to work. And there will be 1.25V between Vout and Adj. And then the battery will have 13.5V. 13.5+1.25V+3V is 17.75V.






                  share|improve this answer











                  $endgroup$



















                    4












                    $begingroup$

                    You need more than 14V at input if you want to charge a battery to 13.5V. About 18V should be enough. LM317 needs about 3V between Vin and Vout to work. And there will be 1.25V between Vout and Adj. And then the battery will have 13.5V. 13.5+1.25V+3V is 17.75V.






                    share|improve this answer











                    $endgroup$

















                      4












                      4








                      4





                      $begingroup$

                      You need more than 14V at input if you want to charge a battery to 13.5V. About 18V should be enough. LM317 needs about 3V between Vin and Vout to work. And there will be 1.25V between Vout and Adj. And then the battery will have 13.5V. 13.5+1.25V+3V is 17.75V.






                      share|improve this answer











                      $endgroup$



                      You need more than 14V at input if you want to charge a battery to 13.5V. About 18V should be enough. LM317 needs about 3V between Vin and Vout to work. And there will be 1.25V between Vout and Adj. And then the battery will have 13.5V. 13.5+1.25V+3V is 17.75V.







                      share|improve this answer














                      share|improve this answer



                      share|improve this answer








                      edited Aug 7 at 11:25

























                      answered Aug 7 at 11:17









                      JustmeJustme

                      6,4412 gold badges6 silver badges18 bronze badges




                      6,4412 gold badges6 silver badges18 bronze badges
























                          3












                          $begingroup$

                          The problem you have is caused by the LM317 and the voltage you have available to it.



                          The LM317 requires a difference of 3V between the input and output voltage. You have 15V from your powersupply (which you drop to 14 with the LM2596.) That's only 1.5V above the output voltage (13.5V) that you need for the battery.



                          You really only have two choices:



                          1. Use a higher input voltage (at least 17V)

                          2. Use a different current regulator that can work with the available voltage.

                          In any case, the LM2596 is only making things worse.






                          share|improve this answer









                          $endgroup$



















                            3












                            $begingroup$

                            The problem you have is caused by the LM317 and the voltage you have available to it.



                            The LM317 requires a difference of 3V between the input and output voltage. You have 15V from your powersupply (which you drop to 14 with the LM2596.) That's only 1.5V above the output voltage (13.5V) that you need for the battery.



                            You really only have two choices:



                            1. Use a higher input voltage (at least 17V)

                            2. Use a different current regulator that can work with the available voltage.

                            In any case, the LM2596 is only making things worse.






                            share|improve this answer









                            $endgroup$

















                              3












                              3








                              3





                              $begingroup$

                              The problem you have is caused by the LM317 and the voltage you have available to it.



                              The LM317 requires a difference of 3V between the input and output voltage. You have 15V from your powersupply (which you drop to 14 with the LM2596.) That's only 1.5V above the output voltage (13.5V) that you need for the battery.



                              You really only have two choices:



                              1. Use a higher input voltage (at least 17V)

                              2. Use a different current regulator that can work with the available voltage.

                              In any case, the LM2596 is only making things worse.






                              share|improve this answer









                              $endgroup$



                              The problem you have is caused by the LM317 and the voltage you have available to it.



                              The LM317 requires a difference of 3V between the input and output voltage. You have 15V from your powersupply (which you drop to 14 with the LM2596.) That's only 1.5V above the output voltage (13.5V) that you need for the battery.



                              You really only have two choices:



                              1. Use a higher input voltage (at least 17V)

                              2. Use a different current regulator that can work with the available voltage.

                              In any case, the LM2596 is only making things worse.







                              share|improve this answer












                              share|improve this answer



                              share|improve this answer










                              answered Aug 7 at 11:31









                              JREJRE

                              28k7 gold badges53 silver badges91 bronze badges




                              28k7 gold badges53 silver badges91 bronze badges
























                                  0












                                  $begingroup$

                                  Also, if the power supply is switched off and the 12V battery is still attached, there's a negative voltage difference (Vin-Vout) on the LM317, a situation not mentioned in the data sheet as far as I can see. If that causes a leak current, it would drain the battery.






                                  share|improve this answer









                                  $endgroup$



















                                    0












                                    $begingroup$

                                    Also, if the power supply is switched off and the 12V battery is still attached, there's a negative voltage difference (Vin-Vout) on the LM317, a situation not mentioned in the data sheet as far as I can see. If that causes a leak current, it would drain the battery.






                                    share|improve this answer









                                    $endgroup$

















                                      0












                                      0








                                      0





                                      $begingroup$

                                      Also, if the power supply is switched off and the 12V battery is still attached, there's a negative voltage difference (Vin-Vout) on the LM317, a situation not mentioned in the data sheet as far as I can see. If that causes a leak current, it would drain the battery.






                                      share|improve this answer









                                      $endgroup$



                                      Also, if the power supply is switched off and the 12V battery is still attached, there's a negative voltage difference (Vin-Vout) on the LM317, a situation not mentioned in the data sheet as far as I can see. If that causes a leak current, it would drain the battery.







                                      share|improve this answer












                                      share|improve this answer



                                      share|improve this answer










                                      answered Aug 8 at 8:02









                                      Arthur HoornwegArthur Hoornweg

                                      1




                                      1






























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