A simple battery charger based on SCR is shown here.Here the SCR rectifies the AC mains voltage to charge the battery.When the battery connected to the charger gets discharged the battery voltage gets dropped.This inhibits the forward biasing voltage from reaching the base of the transistor Q1 through R4 and D2.This switches off the transistor.When the transistor is turned OFF,the gate of SCR (H1) gets the triggering voltage via R1 & D3.This makes the SCR to conduct and it starts to rectify the AC input voltage.The rectified voltage is given to the battery through the resistor R6(5W).This starts charging of the  battery.
When the battery is completely charged the base of Q1 gets the forward bias signal through the voltage divider circuit made of R3,R4,R5 and D2.This turns the transistor ON.When the Q1 is turned ON the trigger voltage at the gate of SCR is cut off and the SCR is turned OFF.In this condition a very small amount of charge reaches the battery via R2 and D4 for trickle charging.Since the charging voltage is only half wave rectified ,this type of charger is suitable only for slow charging.For fast charging full wave rectified charging voltage is needed.

Circuit diagram with Parts list. 



  • Assemble the circuit on a good quality PCB or common board.
  • The transformer T1 can be 230V primary, 18V /3A secondary step down transformer.
  • The voltage of the battery at which the charging should stop can be set by  the POT R4.
  • The battery can be connected to the charger circuit by using crocodile clips.



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  2. Ramkumar

    what kind of battery will charged in the circuit desgin

  3. parmar ramji

    i known more about this project
    t battery charger circuit using scr please help me

  4. Good, nice battery pack charge and discharge circuit design.

  5. Sir,
    Can i use LED for indicating the charging and discharging of battery.

  6. chippa srinivas

    hai could please very very new projects in 2014 use in electronicswith simple projects

  7. Can you please send me more detail[Battery charger circuit using SCR.]

  8. hai, i need to use two scr in this circuit,so i need your help to implement it

  9. plz tell me more details about ths topic n also tell me what kind of battery will get charged?

  10. please send me more details about this project and what kind of battery will be charged by using this circuit.
    Thank you sir,

    • seetharaman

      This charger is for charging lead acid batteries only.

  11. rajagopal

    respected sir,
    am very much intrested in this project..can you plss send me the circuit details along with its application.
    thank you

  12. can u plz send me the design of this circuit. does this circuit charges battery of cellphone? if not what kind of battery does it charge? please reply asap.

  13. Sir,can i use 12v transformer? Pls send me the calculations and circuit explainations. Is Resistor 22ohm 5w the ordinary 22ohm resistor?

    • Partha Bhakta


      The battery can be connected, any polaraty charger clip.


    how can we replace the scr 2N3668 and diode SD50 by another one.How to charge the battery quickly by making modificattions to this circuit.kindly reply please….

    • shajadi parveen

      Battery charger circuit using SCR. IN THIS CIRCUIT SD50 DIODE AND SCR 2N3668 ARE NOT AVaILABLE IN MARKET.
      what is the voltage of the battery to be used in this circuit.
      please tell me. thanks in advance
      can i use 12v transformer?
      And can u send me a calculation and amount of voltagedrop at every resister And doide also

    • Seetharaman

      SD50 is a BEL (Bharat Electronics Ltd, India) bias diode which is not available any more. You can use 1N4148. For the SCR any SCR capable of 250volt PIV and 16Amps current handling capacity will do. Like BT151 2N6401 2N683 2N5206 etc

      • what can we replace SD50 with other than 1N4148 if not available

  15. mushfiq ahmad

    hi admin
    this circuit is very good and i want to know that can we replace scr 3668 by 5604

    • Battery charger circuit using SCR. IN THIS CIRCUIT SD50 DIODE AND SCR 2N3668 ARE NOT AVaILABLE IN MARKET.

      hi admin….what is the voltage of the battery to be used in this circuit.
      please tell me. thanks in advance

      sir I want to know the cost of circuit .And what will be output voltage And what will be output current across battery what type of battery i have to charged and what its cost of cicuit

  16. Nay i know what will be the total cost for this project…?

  17. And can u send me a calculation and amount of voltagedrop at every resister And doide also

  18. sir I want to know the cost of circuit .And what will be output voltage And what will be output current across battery wht type of battey i have to charged and what its cost

  19. hi, i have a 1000va IPS uses 24v, 14AH battery. Now i want to change it to 24v, 70AH for long backup. so pls suggest me what type of modification i have to do it. thanks

  20. Its good but, can we use scr of less rating such as of 1 amp rating

  21. hai can i get the design and calculations of this circuit?

  22. Sir can u help me how to read this diagram? it is a reverse bias?

  23. sir..i woluld like to know about scr..what is scr in the circuit..pls help me as i selected this batery charging circuit as my miniproject

  24. mahesh kumar

    hi guys….what is the voltage of the battery to be used in this circuit.
    please teii me. thanks in advance

    • please send me the voltage range of battery to be charged.also send me the relavant details of this circuit

  25. mahesh kumar

    hi guys….can any body tell me. can i use my mobile for charging.

  26. rsuryanarayana

    i want how this circuit can work and who many volts upto this circuit can charge

  27. naga sai kumar

    can u give me more decription about this….

  28. can u plss help me with the calculations and provide me more information

  29. wasiu adebayo

    I tried my hands on this circuit but the output voltage was just 6volts pls how do I achieve a 12volt output? though I used a BT151 scr instead of the 2N3668 scr. Thanks pls enlighten me u can pls mail me.

  30. this is quite perfect could you please give me more info

  31. rahul pandat

    Hi, i m rahul pandit..i make my project properly.& i submit it .yes ..i done it.

    • what is scr in ths circuit can you pls tell me..because i too selected it as my mini project

  32. can i use this circuit for only charging cut on full charge,
    and get automatic on when battery get low
    can i use battery 12v,24v for circuit supply and connect relay
    of 12v or 24v/60ohms to 250ohms in output for switch. ur daddy navi

  33. ganesh chettery

    can i use this circuit for only charging cut on full charge,
    and get automatic on when battery get low
    can i use battery 12v,24v for circuit supply and connect relay
    of 12v or 24v/60ohms to 250ohms in output for switch.

  34. @seetharaman..can u pliz help me with the calculations and the design?.please.

  35. what changes will apply in order to charge 12v 7.0AH acid batteries.

    please sent instructions or diagran on my mail ID.

  36. How the battery charger working ? i have a liitle problem on my circuit ?

  37. GUYs what is F1/???? and none answered the question what if there is no SD50 and BC148?

    • some says that b e junction should be used as a substitution for sd 50 what does that mean? im new to circuit building

  38. Battery charger circuit using SCR. IN THIS CIRCUIT SD50 DIODE AND SCR 2N3668 ARE NOT AVILABLE IN MARKET.

    • Seetharaman

      SD50 is no more available from BEL, use b-e junction of BC148
      for SCR you can use any 6amps 100piv or greater SCR. Similar to T106 BT145 etc

  39. Dear sir

    Please let me know how much KVA or KW of that transformer and how to connect the bridge rectifier for fast charging



  40. sir, can this charger above charge 13.5v, 200ah and how many hours for full charge? And what can i add to this cgarger to give me full wave for full charging?

  41. i have to design a battery charger with variable input from 3-45 volt dc and out put is 15Volt DC.can any
    one tell me about it..

  42. Can i use this charger to charge 100ah to 200ah battery ?

  43. Thimme gowda

    pls send min projects SCR battery chargers chargers

  44. Mallikarjun N Sidaraddi

    >Can anyone help with the calculations of this design??

  45. Hi boss,I selected this for our miniproject.I’m in the need of the Design Procedure

  46. ciao ho un problema cerco un proggetto di un carica batteria x ricaricare una seria di batterie che in totale erogano una tensione di 48 volt e una corrente di 25 Amp ma io su internet nn trovo nulla mi sai dare qualche dritta su qualche link da provare o se il tuo proggetto si puo modificare x avere quello che cerco .. a mi dimenticavo le batterie che devo ricaricare sn le monolitico sla 4x 12 volt 25map

  47. Dewashish Biswakarma

    Respected sir,
    This circuit had help me to repair my old battery charger,I shall may thanks.

  48. it is ok for +ve half of the ac suply. what about negative half .
    do it works..
    i feel we need to use retifier circuit in the begining of the circuit.

  49. sameer shaikh

    can you plzz send me the datasheet of sd50?i neeed to knw the terminals of sd50?plzz its urgnt

    • seetharaman

      SD50 is no more available from BEL, use b-e junction of BC148

  50. mbongeni john

    Hi, my name is John. I would like to get some help from you. Am designing a car battery charger using an scr, i want to incorporate an LED for fully charge indication on my design.

  51. hi this circuits is very helpful for my invention,thanks a lottttttttttt

  52. Arjun Menon

    Sir thank you for letting me know what battery it can charge… Can you please tell me wether the circuit needs an additional scr triggering circuit. And also can you help me with the calculations and details. my id is

    • hi….frnd
      can i connect transformer
      18-0, 3amp replace by
      12-0, 2amp
      plz reply….

  53. Arjun Menon

    Does this Circuit need and additional scr triggering circuit. And what are the calculations? can you please mail then to me at Can someone please reply to my question. I have asked the Same a couple of times before too but no reply. Please help…

  54. Seetharaman

    Hi this charger is meant for charging 12 volt Lead-Acid car batteries of 30 to 40AH capacity. (not for flat battery for a partially discharged battery)

  55. hello…..I’m gonna submit dis project.can anyone help me with dis?guys tell me what must b done n all…
    n what’s d output voltage? is it applicable to phone battery?

    • Arjun Menon

      it can charge upto 12v lead acid battery it can’t charge mobile batteries…. Can you please tell me if this circuit needs an additional scr triggering circuit

    • yeah its applicable to phone battery output should be 12v

  56. Arjun Menon

    PLease someone tell me if this circuit needs an additional scr triggering circuit please help i have to submit this project

  57. Arjun Menon

    Please tell me if the above circuit requires an external circuit to trigger the scr. As in an additional circuit other than the above is required or not.. Please reply very important

  58. Arjun Menon

    Can someone tell me what batteries can this circuit charge

    • hey did u get to know what batteries can b charged?

    • seetharaman

      Hi Arjun this is meant to charge 12 volt Lead Acid 30 to 40AH car batteries(not for a flat battery). Can be used for charging 12vols 7AH or 10AH battery from fully dischaged condition.

      • Arjun Menon

        Sir thank you for letting me know what battery it can charge… Can you please tell me wether the circuit needs an additional scr triggering circuit. And also can you help me with the calculations and details. my id is

  59. what volt battery will it charge? and what kind of battery ?

  60. hey plz help me i hv a project dat i mst submit a battery charger input voltage is anythng from 60V-150V and the output is 48V pls send me a circuit digram nd wat componet mst i change

    • Seetharaman

      Hi Larry that will be a major modification we may think of a similar project in future.

  61. Electronics Projects

    very good circuit has good application with low cost.

  62. Johnsheen

    I would like to have a circuit idea with primary side of the transformer. May be with an SCR control. That will reduce the current bill and wastage of electricity.

  63. mahesh birajdar

    can i replace scr 2n 3668 with another scr no.
    please give me solution .

  64. Hi.
    I want to make this work for 32 volt 150AH battery with current limit to 15 amp’s charge current. Any proposals??

  65. my email “” ,i hope you reply me as fast as you can,its quite urgent.thanks again.

  66. you use 230v ac,so how about if i want to use 15-25v dc…i mean what is the changes will happens to the connections in the circuit…i hope i can see the new design for the circuit…thanks alot.

  67. Seetharaman

    Hi Pratima sorry i was a bit busy. tomorrow evening, you will get calculation and circuit in your email id.

    • Was going through this project and liked it kindly forward to me the necessary information such as calculations if am to present it to a panel.thank you

  68. hey can u plz mail me the design for 12v 1.3AH battery.
    can u also tell me the watts of the resistors used???
    plz reply fast its urgent..

  69. hey seetharaman,
    plz reply
    its urgent.there was no reply for my previous questions also.

  70. seetharaman

    Hi Keith D1 through D4 is a must for this circuit to work. you may use your rectifier with a 12 volt 10 amp transformer and a 1ohm 10 watt resistance resistance in series for charging 12 volt car battery.

  71. Hi,
    Thanks for posting this diagram. I’ve been looking for a battery charger with an adjustable output and this looks like just what I need. Also, I’ve got a 25 amp diode somewhere in my junk box and I was wondering if the circuit would work OK if I connected it to the output of the transformer and did not use diodes D1 thru D4?

    • please help me in finding the equivalent components for SD50 and 2N 3668.its urgent…

      • ashvin ramani

        please ripley for sd50 equivelent another diode

  72. Seetharaman

    Hi Peter if it is 12volt 200AH battery. You require a 15.2 volts (adjustable to 14volt) regulated and with a current limitation of 30Amps.

  73. hi sir, pls need battery charger capable of charging a 200ah deep cycle battery. Thanks

  74. please helpn me in finding the equivalent components for SD50 and 2N 3668.its urgent…

  75. I want to place LED’s to indicate charging and discharging,LED on while charging and off while discharging,where can i place the LED’s???and how many LED’S?????plz reply fast….

  76. hey,
    my battery is 12v,1.3AH, can u tell me the limiting current and voltage for this???and can u mail me the design and calculations at its urgent..

  77. Hi! you are doing a wonderful job. Keep it up.By the way can you help me with an automatic battery charger circuit using SCR.Thanks.

  78. tell me the designing part of the battery charger circuit using SCR….plz

  79. gud evng…. can you please tell me why the SD50 , BC148 , diodes 1N4001 , SCR @n3668 are used in the circuit diagram of battery charger circuit using SCR…. plz give reply to this…

  80. divya maram

    Hi Seetharaman,
    Can u help with the calculations of this design??

  81. Arisecute

    Please keep up the good work,you’re educating the world thereby. Thumb up for you all!!!

  82. at the load u have only mentioned battery to be charged. wat type of battery is it. lead acid battery or wat?
    and wat is the minimum voltage and current specifications of the battery

    • admin

      reply to binduram
      This circuit can be used for charging 12V lead acid batteries.

  83. Can we use it for a mobile battery also. 3.7v , 3.2Wh

    • admin

      You cant use it for a mobile battery.

  84. mushtaq bangash

    This is good site,,i m a student of gct attock and i regular see the same site.i like so much
    Mushi pcr’ian



  86. seetharaman

    Hi Digvijay For a 12volt 60AH lab you require a regulated current limiter power pack. voltage regulation of 14.4 volt(120% of rated voltage for storage operation)and with a current limiting at 15Amps max(25% of rated capacity). This is the battery manufacturers general recommendation.

  87. Very good web site. Please anyone tel me the circuit to charge 12 volt 60 Ah lead acid battery.

  88. Shams Faruque

    I appreciate this effort where there is a lot of things to learn

  89. I enjoy the efforts you have put in this, regards for all the great content .

  90. i want such circuit diagram which is receive any mobile call in the range of 30 meter ( plz help me any one

  91. Terrilyn Ezpeleta

    Hey Jason, thanks for including Twitter Image in your list.

  92. this is the most consumate tech savvy website ive ever come across as an electronics student..!!

  93. Seetharaman

    Hi john you leave collector (no connections)DC548 should be available. you can use 2N2222.

  94. BC148 is not available in the market here. can i use any npn gen purpose transistor like 2N2222?

  95. thank you sir seetharaman. how about the collector of the BC148? where do i connect it?

  96. Seetharaman

    Hi John Any 6Amps SCR you can use. for SD50 use base emitter junction of BC148.

  97. hello,

    i inquire in the market for the components but not available in our place. will you help me for the substitute for the SCR, Transistor and SD50 diode on above circuit? thank you in advance…

  98. Seetharaman

    Hi Jacob for charging 200AH battery you require a charger capable of 50 amps for initial charging and there after around 10 to 20amps.. if only for trickling to just maintain the terminal potential against self discharge you require 10amps current, which is not available in the above circuit.
    you have to replace and upgrade almost all existing components including transformer to suit your requirements.
    Hi christy i will mail you full details soon

  99. hi sir, i posted a request on if you could help me design a 12v trickle battery charger capable of charging a 200ah battery but uptil now i’ve got no response.Please my dateline is approaching fast. Or can the circuit above handle this? Thanks

  100. Christy Moodley

    Can anyone help with the calculations of this design??

  101. Christy Moodley

    Hi Seetharaman,
    I really like this post,i really like the way you explain in brief when there is a question.I would like to know if i can email you my circuit which i have seen from a different website using the SCR to charge a battery.I’m a student in South Africa and you seem like the person who can help me.I want to email you this circuit,my lecturer says i can use the circuit but i have to modify it.will u help me on how to modify it?

    • Hi Christy can you send me your circuit and results please.

  102. Seetharaman

    Hi Rajesh the same circuit appeared earlier in Circuitstoday can be used. set the limits as per your reqirement with the preset pots. The relay used is a power relay with 35 amps contact rating. It can easily handle upto 7500VA.

  103. it is very useful circuits can u send me a three phase autochange circuit diagramme with high watt (input volt180-240 and watt is 5000va plz send me my mail ………….. thanks

  104. Is there a way to do this for a 9V battery using a solar cell instead of a transformer?

  105. how much cost of the scr battery chager?. i want immediately. please tel me anyone.

    • Hello Vijaya,

      We dont sell Battery charger at this website.

    • please send me the full project report for battery charger using scr.

  106. Seetharaman

    Hi Anil this is suitable for LED Acid or Led acid gel sealed batteries which require constant voltage charge. not suitable for Ni cad or Ni-MH as they require constant current.
    For 12V 7AH battery, ensure that you do not exceed 30% of the rated current of the battery for charging and terminal voltage not greater than 13.8volt for cycle use, that is 2Amps.

  107. Hi, Seetharaman.
    I want to know only that, Is this circuit is used to any 12v 7ah battery?? Or only to lead acid battery.

  108. how can i do the 20ah battery charger plzzzzzzz telll meeeeeeee

  109. goodevening sir,kindly you send the circuit diarram for 1.5v battery,3v battery.


  110. Seetharaman

    Hi Belajar This can be used for a car battery trickle charging. (12volt 40AH. Full cycle Charge 12 volt 10AH battery.

  111. Seetharaman

    Hi Mahmoud in english please, I cannot under stand or read Urdu / Arabi

  112. Seetharaman

    Hi Subarna 12volt 88Amp battery can be charged with a maximum of 30% of 88Amps. That is 25 amps. and tricle charging can be around 8 to 10% of rated current. Butcharging voltage to be limitted to 13.8 volt. so design a power pack with 13.8 volts with 25amps limitting current. or assemble a tricle charger that is 13.8 volt regulated with 8 amps current limit.

  113. هزا البورد لايعمل بشكل صحيح


    sir kindly u talk me plz?my battary is -12v 88AH exid express/i want to make treacle charger/how to make it and what is the circuit? as soon as possible-[]

  115. Seetharaman

    Hi Sundeep you can charge any 12 volt lead acid battery up to 30AH capacity. For batteries of less than 7AH capacity increase R6 to higher value to take care not to exceed 30% of the rated capacity of the battery.

  116. hello can someone tell me what i am going to revise or change in the circuit if i want to charge a 6V battery?? kindly reply asap..thank you so much

  117. Seetharaman

    Hi Jim kindly go through the following site it will give you useful information on charging the battery. for SMF voltage is the criteria and you should never exceed charging current even on rapid charge mode > 30% of the rated capacity of the battery.

  118. Seetharaman

    Hi Jim Chargers are available in the market for 4 X SMF batteries (56 volts with different max current ratings). you have to connect the batteries and series and use the charger,(Provided all the batteries are at the same condition.

  119. Jim Jimenez


  120. Seetharaman

    Hi Jim Jimenez this will charge 12volt battery only. you may have to use 4 nos to charge each of them independantly. or you have to redesign for 48volt.
    Hi Jr Panchal you can use the same circuit for charging 10amp battery also.

  121. Jim Jimenez

    Hello, I have a 4 battery in series to have a 48volt, I use them for my back-up will this work as charger and will be automatic on & off. Thanks..



    Hi I want circuit detail for 12V 10A battery charger regarding details of resisitors, scr’s and diodes and kindly reply me on my mail id which is kindly reply soon


    Hi I want circuit detail for 12V 10A battery charger regarding details of resisitors, scr’s and diodes and kindly reply me on my mail id which is kindly reply soon

  124. Maz_dhono

    Dear Someone,
    If I will give Led for Indicator Lamp
    During Charging with Green Led & After Full Charging with
    Red Led. Where I Can Place This Led ? and how value off
    Resistor can I use ?
    Thank’s for All your Attention.

  125. patrick vaz

    HI Seetharaman, IS there a possibility of adding a toggle switch for 6 and 12 volts charging and toggle switch for slow and fast charging in this circuit.
    thanks a lot

  126. seetharaman

    Hi Lian This charger can be used for 12volts 7AH to 20AH batteries.
    Hi Marron R2 D4 is for ripple charging for topping up. D1 D2 Q1 is for stopping the charging current the diodes are used for sharp switching and isolation. D3 is for protecting SCR gate cathode junction against reverse bias during Q1 conduction.

  127. marronyyy

    why diodes are used in Scr battery charger..??anybody know..

  128. hi guys!….what is the voltage of the battery to be charged in this circuit?i hope for a reply guys….tanx in advance

  129. I need 12v lead acid battery charger with low bat and full indication and adjustable charging current

  130. V Krishna Swamy

    This is the first time i am visiting this site. Its really very interesting where our doubts are answered. Great. I would like to have a circuit for making a home brew Inverter 1000 VA. Simple and effective. I am a HAM and know comething about electronics.

    Looking farward to hearing from you

    Kind regards,

  131. seetharaman

    Hi Me
    Please go through the following site for your requirement. Charging Lithium Ion Batteries are a bit complicated one. If you donot take proper care you may damage the battery permenetly.

  132. Hi is there some one tell me how can I assemble a lithium battery charge? so much thanks for your help.
    best regards Me.

  133. seetharaman

    Hi Robert Connect the secondary of the transformer to a bridge rectifier and then feed it the SCR circuit

  134. Hi I like this circuit and want to build one. I need help understanding how to fully rectify the voltage. Any help for this hobbyist?

  135. Dear someone.I am looking for a 12v sealed lead acid battery charger circuit, the battery must operate leds ,and when the battery goes below 10volt, switches off automatically, it must now be charged again to its full capacity, and so on and so on.
    Looking forward in hearing from anyone, thanks a lot. Regards.

  136. seetharaman

    Hi Vinu what is the battery voltage and AH rating. If it is lead acid battery the charging voltge should be regulated at 115% of the rated voltage of the battery. the current limit should be 25% to 30% of the rated capacity of the battery. These are the safe limits as recommended by the battery manufacturers.

  137. i have a inverter , the charging method is not good,for current limitting capacitor is used ,so the fixed cuurent is going to the battery, so battery not fully charged,any circuit for current limiting instad of using capacitor,

    the transformer voltage is 0v-160v -230v
    i need charger like when the battery voltage increase the current will low,and the battery voltage low the current is high , current rating is 5A to 10A,any circuit for this.

  138. seetharaman

    Hi Kim you are right if the charger is off and only the battery is connected the wrong way. once you switch on the charger the fuse will blow due to battery voltage and charger voltage appearing across R6 Diode and resistance. I agree the diode is ultimately not going to serve any special purpose.
    battery will not get over charged once the terminal voltage of the battery reaches the rated voltage of 13.6volt. the diode anode voltage will be more by 0.7 volt, you adjust the pot in such a way the terminal voltage at the battery including the diode is limitted to 13.6volt.
    the other solution to protect battery reversal will be connect a 6Amp diode, anode to negative and cathode to R1 f1 Junction. If you reverse the battery the fuse will blow indicating the problem.
    with the existing circuit if you reverse the battery and connect. battery voltage in series with charging voltage will appear across R6 and fuse, a very high current will flow, which will blow the fuse. Without R6 the entire voltage will appear across the thyrister the current will shoot up and it may blow the thyrister before the fuse.

  139. Kim Hessel

    Why do we need the R6 resistor? can it be removed?

  140. Kim Hessel

    Nice circuit! To those who wants to put a diode to protect againt reverse battery polarity pls note you CANNOT put it between r6 and f1 or the charging will never stop and the battery will overcharge! putting it on the transformer secondary by pin #15 is ok but has no use! You cannot prevent current from flowing back into the resistor voltage divider network (r3 & r4 & r5) or the battery will start charging again, but you only loose very little power/current (about 12 mA)

  141. Edgardo Diolola

    Dear Admin/Seetharaman,
    Thank you very much for the informations i got.
    More power to you.

  142. seetharaman

    Hi Anil You can communicate me your exact requirement whether a relay should switch of thyristor to be turned off etc to me i will send you a detailed circuit it will be mostly based on “High & Low voltage cut-off with delay& alarm” appeared on Circuits today. very useful circuit idea for so many applications.

  143. Respected All,
    I am doing the automatic 120V Battery charger circuit. For that I need 140V reader circuit. If the Battery Max voltage reaches at 140V it should turn off the charging from the AC supply.
    Kindly requesting please give solution as much as possible.

  144. seetharaman

    Hi Nilesh Sharma If the thyrister is going to get shorted, first the fuse will blow immedeately due high current flow, if the fuse has not failed then the protective resistance R6 will be charred. So nothing will hapen to the battery.
    Hi Edgardo you can use any NPN small signal transistor with Vceo 30 volts Ic max 300mA and Ptot 300mw and a hfe of aroung 150 at 50mA. SD 50 can be any 5volt 400mw zener diode, For the scr what you have got requires a gate trigger current of 30mA it will work as it is if not reduce R1 to 270 ohms


    I have available SCR’s two pcs., #NTE 5545 , can I use this SCR as substitute for 2N3668? of course I will replace the transformer of higher current, same voltage output.
    What substitutes for BC 148 and SD 50?
    Can I have a working circuit for DC motor Speed control using my available NTE 5545 SCR’s of readily available electronic parts in electronics store? Other part numbers are not available here in my country-Philippines.

  146. Nilesh Sharma

    What can happen if the SCR fails? Will it create high current flow to the battery and charging would be at high voltage, resulting in the battery failure/fire?

  147. seetharaman

    Hi Sameh if you are going to use the transformer available with you, yes with a flat battery (which is not supposed to be used with this type of chargers)it may reach 5amp charge current and ofcourse fall down as the voltage builds up in the battery. You may increase R6 to higher value say 2.2 ohms 25watts to take care of it.
    You can connect an LED in series with 3.3K 1/2 watt resistance & one no. 1N4001 diode, between R1 D1 junction to ‘0’ of the transformer.

  148. and i want to put indication led ; to know if the battery in charging mode or not (if battery charging the LED On , if the battery complete the LED Off )?
    thank you…

  149. Hi seetharaman , do i have to get my component resist high current ??(almost 5 or 7 ampere) or what?

  150. MD AET’& CO

    On inspection of the diagram as an engineer, it looks perfect. Am yet to arrange the schematic

  151. Victor Sedere

    This is subject is interesting.
    I like to assemble a battery pulse charger for 12V lead acid batteries with 40…100Ah to prolong lifetime.
    Is it possible to find a good circuit diagram with component list?
    Thank you.

  152. Sayyed Aamir Bashir

    Give me 500w mosfet based pwm inverter

    Sent on a phone using

  153. seetharaman

    Hi Sameh even if it is full wave rectifier instead of 50Hz ripple it will be 100Hz ripple (a full wave rectifier is a frequency doubler)it will get switched of when ever the wave form reaches zero (100 times in a second) so you can go ahead.

  154. ok ok this in case of half wave only …
    but in case of full wave … if i’ll used bridge.. not suitable ,,right?

    srry for many quest .. but i search for practical circuit for my graduated project.

  155. seetharaman

    Hi Sameh the rectified dc is not smoothed with capacitor, hence it will be a pure full wave rectified pulslating DC. so the SCR will gets switched off when ever the supply voltage falls to Zero during every cycle. aging it will get triggered etc. once the terminal voltage reaches the full voltage through R2 & D4 the battery will get topped up at the rate 300mA peak current ripple charging.(trickling)

  156. and the volt through R2 and D4 always go to the battery and charge the battery without controlling

  157. Hi seetharaman ,but the scr cant stop after trigger unless the anode of the scr is zero volt ,right?

    if the scr always on after first trigger <<<<>>>?

    thank you for answer

  158. seetharaman

    Hi Sameh you can use your battery, this circuit suits well. with 12 volt transformer your peak voltage will be 16.8 volt should be just sufficient. the maximum current requirement is 30% of rated capacity that is 2amps, you can go ahead.

  159. thank you for your useful reply..

    i have another question plz >>>

    i have lead acid battery 12 volt and 7 ampere is this circuit suitable for this battery.

    (i have transformer 12 volt — 5 ampere )

    thank you…

  160. seetharaman

    Hi Sameh You can connect the transformer secondary to a suitable bridge rectifier and positive of bridge rectifier to SCR anode and negative to emitter line of Q1 connecting to battery negative. The battery will get the charging current when ever its terminal voltage falls below the set voltage (say 13.6volts). R6 is the current limitter. A flat battery cannot be charged with type of chargers, the minimum continuous rating of the charger should be 30% of the rated capacity of the battery.

  161. how can i modify to 24v battery charger,what component should i change ?

  162. is this circuit begin to charge if and only if the battery is empty == (no voltage output from battery == zero volt).

    or begin to charge if the battery get lower than 12volt (if this battery get 12 volt).

    thank you

  163. seetharaman

    Hi Tutul you can use this circuit for your emergency light application upto 12 Volt 7 Amps battery. set for 13.8 Volt as charge cut off voltage. You can use for routine charge. This charger is designed as a ripple charges without any filter circuit. So it can activate and charge slightly aged battery also. you cannot charge a dud or a flat battery.

  164. hi…..
    do i used this circuit in stand-dy battery charging and emerjency lighting ……………..
    please reply ……………..

  165. seetharaman

    Hi RJ just to indicate few thyristor application, it can be used in inverters. In high current variable voltage DC power supplies to limit the dissipation in the series pass transistors. In high voltage regulated power supplies. as a static high current switch as they require only very low gate switching current. disadvantages are load current should not be less than the minimum holding current of the thyristor. in DC circuit for switching off the thyristor additional circuit is required. cannot be used for high frequency switching application.

  166. what is its output?can i have a diagram with 5V output?

  167. Rjustine03

    nice site!!

    can i request for any other simple applications using SCR’s????

    thanks a lot!!

  168. any other circuit that uses thyristor? thank you in advance!! ^^

  169. seetharaman

    hi twits4twats the other reason for the diode blocking is if the battery is left in circuit and if the charger power goes off the resistance chain will not drain the battery.

  170. good circuit in fact i was looking for a circuit of this type.i want the LED voltmeter for dc volts. thanks.i will be gratefull if somebody should help me.

  171. I ll tell results after my completion project…!

  172. devadas c

    Iam using 2 Nos 12Volt 7Ah batteries in series i need one charger circuit to charge this 24volt please help

  173. devadas c

    Dear All

    Please give me a ciruit for charging 24V (2x12V 7Ah Batteries)

  174. twits4twats

    To protect the charger electronics from accidental reversing of battery polarity kindly add 1N5404 diode between R6 and F1 anode to R6.

    Polarity reversal protection is a good idea although not essential. Place the diode between the number 15 on the transformer and before any other components.

  175. Kindly give me circuit diagram for battery charger of 3.2V, 4.2Ah.

  176. its tooooooooooo good. The people will learn a much things from it.

  177. Seetharaman

    To protect the charger electronics from accidental reversing of battery polarity kindly add 1N5404 diode between R6 and F1 anode to R6.

  178. edi suwarno

    please give me the circuits of battery charger 24v,10A automatic system


    Can you send me the equivalent numbers for the following:
    1. SCR, 2N3668
    2. DIODE, SD 50 ( can i use in4001 instead?)

    • admin

      2N3668~ TYN612

      SD50~ 1N1615, 1N1348A, 1N3987, MR756 etc

      BC148~ BC548,BC107,2N2222 etc

  180. I will be doing this project in my 4th year EE course. I want to ask what are the first things that i should procure for kicking off the project. Also, it is a 20 watt bulb that has to be connected across the battery terminals. For that, what necessary modifications need to made?

  181. hey this circuit is used 4 which type of battery i mean 4 a car baterry or invertor baterry of cell etc……………n upto which volt???

  182. Afif Khan

    I am in need of circuit that when i charge my 12V car battery and when it is fully charged the circuit should discontinue the chargeing and should inform through beep or LED blinking.

    I will be greatful for helping me out of this problem.

    Afif Khan.

  183. edgardo diolola

    i am working here in kuwait.
    I have problem buying electronic parts here, since i came 5 years ago, this country has no enough electronic parts on stock.
    Can you send me the equivalent numbers for the following:
    1. SCR, 2N3668
    2. DIODE, SD 50 ( can i use in4001 instead?)

    Thanks, and this site is very helpful to me, and helped a lot on my job as maintenance supervisor for food machineries….

    Best regards,,


    • Sir can you send me the equivalent numbers of the list you mentioned.

  184. how can i modify to 24v battery charger.what changes are required to modify the circuit.

  185. thanks
    good website for all peson which want to get knowledge about circuit.

  186. How do I modify to Automatic 24V Battery Charger. what component should i change ? thanks

    • amit kumar singh

      how can i modify to 48v 12amps battery charger.what changes to modify the circuit diagram…design calculation also hepl me