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    This is the modified version of the Fast Charger circuit posted earlier. This circuit has Auto cut off facility also. This High current charger can be used for the Fast charging of sealed lead acid batteries used in Automobiles, Inverters etc. This charger can give 5 Ampere current for quick rejuvenation of the battery. It uses an Adjustable voltage regulator so that 6 volt and 12 volt batteries can be charged. When the battery acquires full charge, charging process will be terminated.

    LM338K is a high current variable voltage regulator that can provide 2 to 25 volts DC with high current output. Its important features are 7 Ampere peak output current, adjustable output down to 1.2 volts, thermal regulation etc. It is easy to use and require only 2 external resistors to set the output voltage. The time dependent current limiting ability of the device allows peak current of up to 12 ampere to be drawn for short time. So that it is useful in heavy transient loads and speed start up.

    LM 338 Variable Regulator

    Design considerations

    Use of external resistors

    LM338 K is available in metal can package TO3. K suffix metal can. It has only two pins – Vin and Adjust. The body of the device acts as the output pin. On the bottom side, the first pin is adjust and the second pin is Vin. LM338 requires heat sink to dissipate heat since it is draining high current. Two resistors are required to set the output voltage. Resistor R1 (220 Ohms) act as the programme resistor. Usually 1.25 volts reference voltage (Vref) develops between the output and adjusts pins. The reference voltage is impressed across the programme resistor R1.The voltage across R1 is constant so that constant current flows through the output set resistor VR1.Therefore output voltage is

    Vout = Vref (1 + VR1 / R1) + I Adj VR1

    Use of capacitors

    Two capacitors are usually soldered close to the input and output terminals. C2 is the input bypass capacitor. Output capacitor C3 gives stability for the output current.

    Circuit operation

    Input voltage is obtained from a 0-15 volt 5 Ampere secondary transformer with the 10 Ampere KBPC Rectifier Module. Capacitor C1 makes the DC ripples free and around 16 volt DC enters into the Vin input of the regulator. VR can be used to set the output voltage from 2 volts to 15 volts. A digital panel meter is used for measuring the output voltage. Ready made LED or LCD panel meters are available at reasonable cost. This can be directly connected to the output. So by adjusting VR, it is easy to see the output voltage in the meter. If the output put voltage reduces due to line voltage drop, it can be easily detected through the panel meter. The panel meter also can be used to measure the terminal voltage of the battery. If the power supply is switched off, meter shows the terminal voltage. If the voltage remains steady, it indicates that the battery is fully charged and holding charge.

    Auto cut off circuit is built around the 5 Ampere Darlington NPN transistor TIP122. When the terminal voltage of the battery rises above 12.5 volts, Zener diode ZD conducts and inhibits the working of the Regulator LM338. When the battery voltage drops below 12 volts, Zener turns off and the regulator again provides charging current.

    Fast Charger with Cut Off Circuit Schematic

    Fast Charger with auto cut off circuit schematic

    Fast Charger with auto cut off

    Setting the output voltage

    A fully charged 12 volt battery should have a terminal voltage of 13.5 volts and that of a 6 volt battery 6.5 volts. To charge the battery, set the output voltage for charging as 14 volts for 12 volt battery and 8 volts for 6 volt battery.

    LM338 on Heat sink

    Use heavy gauge Red and Black wires in the output and use crocodile clips for connecting the battery. Before the charger is connected to mains, connect the clips to the battery terminals with correct polarity and see the terminal voltage. If it is less than 13.5 / 6.5, switch on the charger and charge up to one hour. Wait for 10 minutes and again check the terminal voltage. If the voltage remains steady, the battery can be used.

    LCD and LED volt Meter

    TIP 122 Pin connection

    attentionThe author D Mohankumar is not an active member anymore. Please take into consideration that the presented information might not be correct.
    ask a question

    141 Responses to "Fast Charger with Auto Cut Off"

    1. Shaheen Shahid says: on May 12, 2010 at 8:26 am

      First of all thank you so much for the circuit diagram. Dear Sir this circuit can charge 12V 100AH Car/UPS Battery or not ?? Please reply

      • I want to ups battary charge sir you help me.Charge full volt cut.please help me.

      • D.Mohankumar says: on November 24, 2010 at 3:51 am

        If your UPS battery is 12 V, You can use the same circuit

      • sudharshan says: on December 18, 2012 at 11:20 pm

        Hi sir i am sudharshan. i want your help, why because i did a project with very powerful data. but this project depend upon DC and AC mixing. so i requist you pls help for complete my project Thanks inadvance

      • in ur ckt sir,,i think we must use zener diode with a ref voltage of 13.1v/1W,THEN WE SET A CHARGING VOLTAGE OUTPUT OF 13DVC,,,13dvc is higher than 12 dc battery just to charge the battery…so when the battery got full chrged of abt 13.1vdc,,thats the time stop the chrging processs…i think so…thnk u sir for ur ckt tht gives us more info abt power supplies.. :)

      • hellow sir sir did u explain me …..what is the peek fuul charge point of 12volt battery????

      • Terrance says: on June 5, 2012 at 5:31 pm

        I made a great charger .the transformer working always,,Think the battery is low,charger connected automaticaly..sudennly battery voltage rise up to transformer voltage,,i have a solution,but how will i upload this circuit for this page,,,,

    2. You can use the circuit.It gives 15 volt DC at 5 Amps current.Use heave gauge wires to connect the battery. Battery will not take much current during charging. A partially discharged battery takes 1-2 amps current during the initial stage.Then it goes down to 500 mA or less. It is better to charge Lead acid battery with “Dirty DC”. That is Rectified DC without Smoothing in a capacitor. Pulsating DC is better than ripple free DC for charging. Simply connect a 8-10 Amps bridge rectifier module to the transformer secondary and use DC for charging

      • sudharshan says: on December 18, 2012 at 11:19 pm

        Hi sir i am sudharshan. i want your help, why because i did a project with very powerful data. but this project depend upon DC and AC mixing. so i requist you pls help for complete my project “sudha2894@gmail.com” Thanks inadvance

    3. Shaheen Shahid says: on May 14, 2010 at 10:56 am

      thanks for the help

    4. I am interested in LM338 . I am thinking to replace my LM317 with LM338 . If I want to add a LED indicator in the circuit . When the circuit is in Cut-off status this LED will glow up to indicate .

      Where and how will I add this LED incicator with transistor TIP122 ?

      Vout = Vref (1 + VR1 / R1) + I Adj (VR1) . Sir, Can you give me little example for this calculation ? Specially I don’t understand Vref and
      I Adj (VR1) .

      – Thanks

      – Neon

    5. Sir, How can I add a LED indicator to indicate the cut off status of the circuit ?

      – Thanks

      • Hello Neon, good day!
        Did Mr. Muhankumar gave u already the ckt for the indicator when the charger is in cut off mode?
        Can i ask one? Please send me thru this email..”adasma@yahoo.com”
        Thanks a lot.

    6. thanks for the circuit. i liked the circuit and i am going to build it. but i have some doubts:

      1. in your comments you have said ti remove the filter capacitor after the bridge rectifier. but the data sheet of LM338 says to use the filter capacitor so that the input to it be ripple free. so should we use it or not?

      2. in circuit diagram of fast charger without auto-cutoff the capacitor values were 50v but now in this circuit with auto cut-off 25v capacitor is used. does the value of the capacitor has no effect on the output if the circuit?

      3. here by using the potentiometer at adjustment we can vary the output voltage but if we want to change the output current how we can do that?

      4. also if we use 0-18v transformer what extra changes has to be made except the rectifier?

      • D.Mohankumar says: on June 13, 2010 at 7:13 pm

        Your doubts are genuine. I appreciate your interest to clear doubts before making the circuit.
        1.If you use the circuit as such, a filter capacitor is necessary. I mentioned the charging using dirty DC is about a simple transformer and diode charger.
        2. Usually the electrolytic capacitors should have a voltage rating double than the supply voltage.It is always better to use a higher value capacitor like 50V
        3. current can be adjusted using a series resistor at the output. Desired current can be calculated using ohms law.If a pot is used, the current can be varied. But it should have high current handling capacity.
        4. no change is required in the layout. Increase the value of electrolytic capacitors to 50V.

      • 1.if i want to change the output current to 2.5A then what should be the series resistor value and rating should be?

        2.as this is auto cutoff can the charger be kept switched ON for 24 hours?

        3.also for 6.5A transformer which diode for rectifier should be used?

        a great thanks for the reply of my previous doubts.
        once again thanks for that.

      • D.Mohankumar says: on June 14, 2010 at 5:34 am

        It is difficult to reduce half current through a resistor. So use a 0-15 / -18 – 3 Amps transformer
        You can keep it on but occasionally monitor the charger
        The same rectifier can be used.It is rated 10A

      • Sir .. I wt design a mobile charger for constant output ad auto cut off .. Help me

      • sir i need a automatic switch on/off

        when battery voltage is 11.5v switch on
        when battery voltage is 14.5v switch off


    7. i have implemented the circuit with 0-18V/2A, but i have not got the desired output i.e. whatever be the value of VR1 the output voltage always remained at 1.5V and current of just 100mA.

      then i have changed the transformer to 0-18V/6A then to the output was 1.5V/100mA.
      i could not find any error in my implementation.

      so i have removed the feedback path i.e. the zener and TIP122, now i got the variable voltage from 1.5V to 17.5V/2.2A.

      what could be the reason for the error and by using the 6A transformer why i am getting only 2.2A maximum for charging 12v/45Ah lead acid battery at the output voltage of 13.8V?

    8. The problem may be due to fault in zener/Tip 122 / LM338.Since high current is flowing, heavy heat will be generated. If heat sinking is not adequate, it may affect the output. Give heat sinking for both transistors. Zener may be opened. This will sink current to the negative rail. change the value of VR to 1K and use a good quality pot

      • It also occurred to me that zeners are sometimes installed with incorrect polarity even by experience technicians by accident. Something to check anyway.

    9. sir can you please tell me if i connect 13.5 v zener diode instead of using 12.5? the description says cutoff situation will build around 12.5v i believe it should be 13.5v( 13.8v max charg voltage of battery)

    10. Muhammad Tanveer says: on July 2, 2010 at 9:47 pm

      sir i have implemented the circuit and it is working very good but there are some problems i am facing. first of all i am getting voltage of 13.3Xv for charging but i am unable to get it to 14v. i am using a transformer 12-0-12 6amps.is it because of voltage drop across rectifying diodes? should i use germanium diodes for rectification of which voltage drop is 0.3v(0.6v for full wave rectifier which uses 2 diodes)? will i be able to get 14volts at the charging end then or is there any other way?

      and secondly i connected an ammeter in series with it to measure the current, i observed i was getting only 0.7amps. can you please help me with this?
      i am basically trying to build a UPS and use your circuit to charge the battery, will it be able to charge the 200Ah over a continuous period of time?

      please i need your assistance very urgently.
      Thanks in advance and many thanks for your circuit. its perfect if the problems are solved (for me) :)

    11. sir please provide me the working of TIP122 as a switch pleaseeeeeeee

    12. sir is this charger can be use in cellphone???

      • D.Mohankumar says: on November 20, 2010 at 3:41 am

        No this is a high current charger for Lead Acid batteryr.Mobile battery needs only 3.6 volts ans 100 mA current for normal charging.

      • Dear Sir,
        I want circuit of 24VDC / 5A charger using LM317.
        kindly suggest..


    13. can i charge 12V 200ah deepcycle battery with this? thank you for your reply

    14. Sir, i have one doubt. how much time taking for full charging of 12 v 100 ah battery with this charger.

      • D.Mohankumar says: on January 8, 2011 at 4:46 am

        Time of charging depends on how much charge is available in the battery

      • if 20% charge is available in battery how much time will take

      • D.Mohankumar says: on January 14, 2011 at 3:48 pm

        Dear Satheesh

        The charging time depends on many factors, like condition of the battery, input voltage and current, temperature etc. If the battery is a new one, and input current is high around 2-5 amps, it will take 1-2 hours to complete the charging process.

      • DAGOGO-HARRY, S. A. says: on August 26, 2011 at 6:15 pm

        what about 12v/200ah battery charger schematic? can i get one from you?

      • n ur ckt,,the zener is 12/1W..it wrks when 12vdc is reference ryt, then on setting chrged is 14 volts dc…i think the zener is always active tht always to shut down output coz more than 12 volts activate the zener to conduct ryt??pls explain..thnx sir

    15. what is the process to obtain 5A current from the transformer? my lecturers have told me that 5A transformer is a very large one, and the circuit is wrong?? how far are they correct?? please help me out. ..

    16. I entered this site today by accident when i was looking for a circuit diagram but i discovered that is good for young inventor like me. So keep up the good work your are doing in this site. Thanks

    17. Hi sir.. it’s a very nice circuit design you have here… but i seems to be having a problem… i changed the following parts to suit my application:

      LM338 to LM317
      2V-15V to steady 6V
      Zener Diode 12V to 4.3V

      The rest are the same… But it seems that the OUTPUT VOLTAGE remains @ 3.5V whenever the AUTO CUT-OFF CIRCUIT is engaged even if i change the output voltage of LM317 to 8V or 9V… Could you please enlighten me…Thank you very much

    18. sir
      please give me a cercuit that chargeda 12v 200amp invarter battery.pleaes sir help me

    19. oh sir
      my domestic ac power is up and down, so my charger charged my battery some time full some time half.i want a high amp charger that charged my 200amp battery conostantly and my battery kips longlife.tahnk you

    20. for those who have doubt in this project!
      I already made this project about 20 times or more and theres nothing wrong with it! the circuit is good. no modification needed or indication needed for this project, just follow the simple circuit and your good to go.
      next month i have to mass produce this simple circuit for future use! thanks for the author!

    21. Can i use the charger to charge a battery that requires an input of 13v but do not know the required charging current? pls it’s urgent sir.

    22. I appreciate your effort to start with but I see some questionable situations in your circuit even before building it:-

      1. The IN5402 diode has a Maximum forward average rectified current of 3A as given by its datasheet, how is it able to guarantee 5A as you claim?

      2. The zener diode connected to the darlington pair transistor indicated there has a 12v rating how does it begin conducting at 13.6v to stop the charging by interfering with the LM338?

    23. can i charge a 12V/120ah SMF battery with this??????????????

    24. EVERYONE please don’t build this circuit. it is the most awful circuit that doesn’t work. i have tried to build it several times. it cant automaticallly charge the battery. first of all the filtering capacitor is way below the value. for about 5 ampares of current it should be about 10000uF… if someone has knowledge of pic microcontrollers he/she can build a fully working charger using ADC/DAC technique…
      simplest technique is to use a 741op amp as a comparator which compares the present voltage with a preset voltage of 13.6Volts.
      dont know why people are so much interested in this stupid project.

    25. YES it does work! “dont know why people are so much interested in this stupid project” because it works!I dunno about you! I already build 63 automatic battery charger for this circuit, by the way u should modify it, hehehehehe! good luck!

    26. DAGOGO-HARRY, S. A. says: on August 20, 2011 at 7:12 pm

      what a 200ah battery charger schematic? pls, can i get one from u?

    27. Dear Sir,

      As you mentioned this circuit inhibits the charging if battery voltage reaches 12.5V and if I use 13V ZD can I have more charging for the battery and do I need to change the base biasing resistor of 1k/1w or can you suggest how to modify this circuit to charge until battery attained 13V.



    28. Sir i have ups coil with multiple wires comming out out the coil i want to use the same coil for batter charger and also want to add full battery charge circuit with buzzer or led indicator. please help me out.

    29. Tanno. U are not expectet to ask anybody not to build the cct. D same cct u claim not to b workin is d same muammed tanveer claim to work fine.you nd tekong are one way trafic. U cannot expect no challenge from a cct designed by somone else.If you dont face any challenge, how would u appreciate and honor the author’s work? D best way to approach things like dis is to express ur gratitude for the author to have disclosed the circuit he has, let him know the effort u hv made so far and then lodge your complaint. You dont expect somthing good to come that easy. He will be happy and ready to help you out. Afterall he is not asking anybody to pay? Go through the comments and see how he was able to answer Probir question bcos of his intelligent approach. More greese to your elboe D.Mohankumar

    30. sir pls reply to all our doubts.. u said 12.5 zener but we need 13.6 as fully charged .. kindly reply fast..

    31. On August 11, 2011 at 3:53 pm,Sir I asked you some questions. By your silence am lead to think you don’t understand circuit analysis. Is this the case? If not so kindly explain my questions.

      I have opted to use a bypass TIP 147 (10A transistor) in conjuction with an LM317T compared to just LM338 which costs thrice the total of the TIP 147 & LM317T.

      Will update on whether it can really get to 10A

    32. Sir,Thanks for your kindness on assisting Electronics schoolar like us but i face one problem may please,assisting me in this. Which charger is best to use on charging a 12V150AH Lead acid battery especially the current size of a charger.

    33. Sir, I saw your Circuit and i have a one question to ask from you. Sir Can you give me a instruction and a circuit diagram for 24V, 40A and 60A Battery Charger. Thank you Sir

    34. Dear Sir, few questions for you:
      1. I have 42 AH SMF battery and as per the manufacturer it would attain full charger between 13.8 to 14.2 V. I did apply 13v Zener instead of 12v Zener but I see by battery does not charge full. Can you put a variable pot in this circuit that can set a cut off voltage (as per need)?
      2. Your LED is just a power LED, can you provide a LED that only glows when the full charge is attained?
      Please help as I have already invested in this circuit.
      Thanks in advance….Anmol

    35. Dear Sir,
      What is the compoment at the base input
      of Tip 122 ? it say ZD 12v 1W but all I
      see is a resistor with no VALUE.
      Can you please be kind enough to let me know by email reply?
      Thanking you in advance.

    36. Friend – my personnel advice to you all:

      This circuit has some issues for sure. I created this circuit exactly same with same components and here is my findings:

      1. The circuit does not work, even if the battery is half charged it will transfer low voltage for charging i.e. float charge. I have well verified these with good voltage and AMP meters.
      2. The diode used in this circuit is of 3 AMP, not sure how it will support 5 AMP configurations.
      3. The LED indicator is just a power indicator, not sure how you will know when actual battery charge has been achieved. In short no indicator.
      4. I have tried using 13v, 14v Zener diode also, but this circuit does not work.
      5. For LED, a 1W register (R3) has been advised, this shows bad knowledge of electronics having known that LED can easily be used by ¼ watt register.
      6. There is a confusion created for using another Zener Diode i.e. for TIP122, its confusing, actually it’s a Register of 1K 1W.
      7. The pot VR 5K, is actually a voltage regulator i.e. to decrease the charging voltage. It’s not for adjusting the cut off voltage for charging.
      With so many issues, please don’t waste money around INR 250 to buy all these. My money is lost.

      Please use this circuit if you want to make a 5-6 AMP 12v battery charger with auto over charging protection feature. I have made this successfully with these changes:
      1. BT136 – This can work upto 4 AMP only, so use BT137 that can work upto 8 AMP.
      2. BRX49 = 2N6565 = 2N883 = 2N891 (You may need this alternative SCR for Q2.)
      3. Use 6AMP diode for rectification i.e. D1.
      4. For R6 use 1K ¼ W resistor (use of 1K Reg for LED is best recommended up to 18v)

      Charger Tips –
      The charging voltage should be 15% to 25% more than battery standard voltage.
      The charging current should be 8% to 12% of battery AH value.
      Example – if you have 42 AH 12 volt battery, you should use the charger with:
      Input charger voltage – 13v to 15v
      Input charger current – 4 to 5 AMP

      I hope I have resolved all queries that you would need.

      Dr. Sinha

      • thank you Dr. Sinha, i appreciate this useful suggestion. I will sure give it a try and report back to u.

      • can you give me a diagram for a digital voltmeter? please?

        thank you :)

      • Dr. Sinha says: on January 16, 2012 at 11:40 am

        I am so sorry, but I am not a doctorate in electronics and I do not know so deep electronics. But I have a advice for you:
        Digital voltmeter and LED voltmeters are easily available in electronics shop. You should get it very easily in very less price as these are embedded IC based circuits.
        You may easily find a circuit to make it too, but believe me such circuit are very complex to make and would even take 10 times higher cost to make than you can actually purchase ready made.

        Dr. Sinha

      • Thanks Dr. Sinha, I appreciate your solution, I always seen D.Mohankumar’s circuits won’t work and he don’t responds to the queries properly.

        I see many people here querying same thing saying this circuit is not working as it mentioned. I also did this circuit for 6 volts battery, but do not see the results. I used 6.8v 1W zener and LM317 regulator.
        1. POT is unable to give more than 7 volts output at 317 PIN2, hope this is due to zener active always.
        2. I do not understand the purpose of TIP122 here, switching can be done by BC547 also. But either not working.
        3. LED at pin2 always glows, it should glow when we connect Battery and off when Battery reaches its charging limit.
        4. Finally it’s unable to cut-off

        I’ve gone through many comments and see these issues from many, I do not know whether they got solution or not.

        Can any one confirm me if this worked for any one???

        D.Mohankumar is this circuit tested and worked for you???

    37. hello sir ihave 60v 3amp smps chager that continus chariging ckt isnot off how to conect use this is ckt

    38. Sir, how i can make a 6v DC charger with medium, low and full indicative led. Additionally, i want to know how the power circuit of DVD player can convert from AC to DC?

    39. Hi sir;
      i want to use this charger to charge my 24v SLA battery (2, 12v, 7AH batteries in series). what changes are necessary in this charger to make it for 24V battery.

      i think i should use 27v zener diode for auto cutt off. but by using this i will not b able to set the output voltage of LM338 equals to 28V. and also guide me please that may i use C828 or C1383 npn transistors instead of TIP122 because the current at adjust pin to ground is very less in mili amperes i think.

      hope you will reply me.

      Thank you in anticipation

    40. and sir also guide me about that, where should i insert the LED that shows the completion of charge. the LED should light up when charge is completed.
      hope you will guide me.
      Thank you

    41. Dear Mr.Mohan Kumar,

      Can this circuit use for 24V,42AH battery?? If Not,Kindly support me for charging 24V,42AH battery.


    42. Hello sir,
      I want to make car battery charger 12v.how much amp is need for ordinary 12v battery can u plz sent the circuit & direction to make it.

    43. hello,

      thank you very much for sharing your knowledge about circuits. i just want to ask you a lil favor :) can you make a diagram of a digital voltmeter? i will use it together with your fast charger :)

      thank you

      • for a digital voltmeter you must have the knowledge of using LCDs, Microcontrollers 8051s etc and u must have ADC either separatly or built in as in PICs and AVRs. all you have to do is to take a sample of output votage from and infeed it to ADC and out put of ADC is feeded to microcontroller where u have to program it to display on LCD screen. Shortly for a DVM u have to use only 3 main things; 1)a controller. 2)an ADC and 3)an LCD… rest of the work is nothing but programming.

        carry on :-)

    44. Sir, Can i use two numbers 12 volt 100 ah “sealed lead acid batteries” in parallel connection with luminous ups/inverter

    45. No sir is there to answer the posts… :-)

      @Edamury: yes you can use 2 batteries in parallel. by doing this the back up time of your UPS will be double…

    46. Can this circuit be used to charger 24 volts batteries? If so ,what part values need to be charged.

    47. i was searching for a good project……. after reading this ……… i think it was quite k……..

    48. please i need a 12v lead acid trickle charger circuit with voltage digital display and auto cut off facility

    49. Please i need 6v bat charger circuit with auto cutoff facility.

    50. simple question.. Im looking to use a 2-7v variable voltage device with a small led screen that measures by the .1 scale. any suggestions? also I would like to attach a small fan to that same device in a 2 inch cylinder. Im am just starting to mess with electronics..and i would like to use some sort of rechargable batteries and keep them on a 5 second time limit for use.. is this possible? if so what connections would i need? Again im sorry in advance for not knowing anything about electronics..Thanks

    51. Adeleke Zakariyau says: on February 12, 2012 at 7:14 pm

      Hello, is it possible to connect the inverter to this charger? When it possible, is it possible again to connect the output voltage of inverter back to the charger? If it is not possible enough, is their any changes made to it? Because of recycling of the battery.

    52. Hello Sir, What adjustment can be made for this charger to be able to charge a 24 Volts (Two 12v, 200ah battery connected in series)with this circuit.

    53. If you want 1A to 1.2 A there isn’t any problem with LM317 circuit, but if you want 1.5 A to 2.5 A or more, then you have to add Darlington transistor, use serious heat sinks and free air flow. L shape aluminum profile 1” by 2” can do the job well, to dissipate the heat, but you cannot enclose the circuit in a compact area. Adding in serial, at positive output, a 12 V bulb, is the best insurance to protect your circuit board from a shorten circuit.

    54. Sir i have to charge a 12V 66AH lead acetate battery the battery must give 4 hours backup and the load on battery is about 11AH. the battery must be charged at the same time while in use which circuit do u recommend for this because i need to charge the battery fully in about 6 hours please reply

    55. Sir i have to charge a 12V 66AH lead acetate battery the battery must give 4 hours backup and the load on battery is about 11AH. the battery must be charged at the same time while in use which circuit do u recommend for this because i need to charge the battery fully in about 6 hours please reply sir

    56. Hello sir..

      I am working with solar power batteries i need to monitor 12v 100ahpms battery voltage and current level on lcd display can you pease give me circuit diagram.


    57. Shivdeep kumar says: on March 5, 2012 at 9:19 pm

      SIR I WANT TO CHARGE 12V , 150AH batery by a mobile charger. please help.

    58. am inspired by this site and specially bye the author…….

    59. Can I charge a Lucas 12V 45Ah battery with this circuit?

    60. Dear sir
      how many V and amps need for good ups battery charging, i have three 190amp battery ups….but charging level is too bad.

    61. sir,
      i am from tamil nadu. here power cut implemented upto 10hrs per day.we are using 600w inverter 150 ah battery. i am unable to charge my battery so backup time also reduced.i want to connect to a solar panel.
      how many solar panels required to charge our inverter do you have any idea.

    62. Thank’s for your information fast charger.

    63. Thank so much 4 the circuit diagram but please I am new in electronics and I want to use this charger also for 24v
      That is 2 12v battery conected make a 24v
      Pls tell what to do tru my mail
      Thank u, Sir.

    64. sir, is it possible if i use transformer 0-15v 600mA to charge 12V SLA battery?

    65. yees,thats a very simple ckt for auto charger

    66. pls i need inverter circuit from 1000w to 5000w . with mosfet

    67. sir, thanks you for the cct. please can this cct charge two deepcycle of 200AH in parallel?

    68. PLS SIR.
      I need the circuit diagram for 12-24 volts 600 amp

    69. Syed Ashraf Yousuf says: on June 8, 2012 at 11:53 pm

      Why my comments has not been published? Requesting to publish here.

    70. Hi.
      I need circuit. when 12v battery low 10v than cut off. low vot cut off circuit can you give me?

    71. i am working with BSNL.
      i want to disconnect/cut-off 200AH BTY at 46V to prevent BTY DeepDischarge.so can any body help me design such a CKT. i have to maintain 100 sites and i can use my old powerplant contactor of 48V. (it’s controler ckts are faulty).

    72. Hi sir,
      I would like to help me and design a battery an automatic /cut off battery charger which can charge a battery of capacity 200AH let it be a lead a cid /aflooded type.
      I will be grateful your quick response
      regards moses kaluya.

    73. Sir,
      I want to design a UPS having the following ratings:

      >not less then 800 watt.
      >I want to run my PC, TV, maximum 4 energy severs and at least 3 ceiling fans with this UPS.

      So, Kindly let me know,
      which types of ICs will be better for these requirements.
      What should be the minimum current rating of transformers, diodes, resistors and capacitors?
      Hopping for a good and early response.

    74. Ganta.Dileepkumar says: on July 4, 2012 at 4:55 am

      Respected sir,

      My name is g.dileep kumar and I am studying final year eee . I was interested in work with electronic projects.I have your previous fast charger circuit diagram and the present fast charger with auto cut off.In the previous one a center tapped 5A 12V transformer is used with full wave rectifier circuit.I want to know in the place of 10A KBPC rectifier can I use the pervious full wave rectifier used in the earlier fast charger circuit.

      Thanking you sir,

      Yours faithfully
      G.Dileep kumar

    75. Hello sir, i have a simple problem
      1.In our home we provide 220v 50Hz of electricity to electronic appliances with so many amps, the transformer decides the voltage and selects how much current it needs.
      2.But in lead acid battery charging we provide selected voltage and desired amps i.e 4amps, 2amps, 5amps for battery charging.
      3.So on which basis it is bifurcated, usually electricians says 3amps is maximum for charging and not to exceed that, could battery decides the amount of current it need i.e if the charger output is 12v 5amps will it take 12v 3amps or required amps as transformers in home appliances decides. Kindly reply sir i am stucked in it.

    76. What is the output amperage of the transformer?

    77. hi sir i am confuss with the compoment at the base input
      of Tip 122 ? it say ZD 12v 1W but all I
      see is a resistor with no VALUE and the VR 5k is it just to connect either the first or the last pin with the sec pin?
      Can you please be kind enough to let me know by email reply? Thanks.

      • Jim Keith says: on July 31, 2012 at 10:47 am

        The resistor at the base of the TIP122 is 1K 1W, but I see no reason why the power rating should be this high. 1K, 0.25W should be OK.

        Regarding potentiometer VR, the resistance should be maximum when rotated clockwise so that clockwise rotation increases the voltage. Experiment on the bench before wiring it into the circuit.

      • Hi,thanks Jim Keith …

    78. good day sir please i need a circuit for a 12volts 10 amps battery charger with auto cut off.thank you sir.

    79. Dear sir,

      Please send how to charge the battery and automaticly cut-off after charging cumplet (12 V battery).
      If that type any kit avelabel in market please send that name.

    80. Due to “high”current=charging%L388.is rate@(5amp) so adjustable regulator*capable of supplying in [excess¤ 5amp<over a range of (1.2v) *to*(32v) and in this schematic%diagram {DVM} is used to display the output voltage ,. . and {dvm} is a high%§=component.is not available in many electronics store. and dvm is not necessary..while connecting emitter direct with positive (GREEN=LED)..to gnd this will serve as cutoff indicator….the other green led will change to (RED=LED) vice versa ,the red led will indicate charging….and rember to change ur zener to 15v..because drop voltage will between two led indicator at least 4v….D5=IN5402 cannot withstand 5amp current it will geting hot..this will lead to excess of damage the diode..Diode=6A4 will be ok,,,as flow back….

    81. This%is very rate to {charge} any inverter§battery=@electroschematics.com..well post….

    82. This%is very rate to {charge} any inverter§battery=@electroschematics.com..well post….but is necesarry..to susbstitue some component,. .and get some changes of this project…this is giving by {johnny@dmohankumar.com}

    83. can we remove the transformer with a ceramic capacitor.
      because the transformer is costly and heavier as compare to the capacitor.

    84. Hello D.Mohankumar, I’m interest on this circuit and its potential!, Do you think this could work on charging a Zune or iPod quickly? with the 5volt regulator of course.


    85. actually.DEVKARAN,you are right but the only thing is that it is difficuit to get high current in ceramic capacitor1 .e x rated capacitor..for high current transformer is neccessary execpt..current rate@500ma or below….the real fact is that..you may found diffcult to buy this xtrans..is very expensive ..just wind it by ur self used large wire guage@secondary and smaller wire guage@primary….i think this will be ok for u

    86. In this high current application, it is not feasible to replace the transformer with an off-line X capacitor current limiter. This would require a 440VAC oil filled capacitor that would be very large and cost far more than the recommended transformer.

    87. Hello!
      I am writing from Russia.
      I have collected on your schematic LM317 chip, which had led to the exit, but it was bad because of the fact that, after the sun hiding, then the battery is discharged through a zener diode?
      I removed from the circuit and a zener diode LED, and then earned a perfect scheme.
      Sometimes, the output voltage of the charge controller is not more than 14.30 volts (why?)
      And now I want to make a controller for battery charging current is adjustable 5-20 amps
      I ask you, and send pomogoite scheme.

    88. sir please tell me what is correct charging cut off voltage of Acme series 12ndf 155Ahr 12volt battery,i would be very thank full to you.

    89. Sir, I have a 600VA UPS with 7A battery. I would like to add 45 Amps battery instead of 7Amps to increase the backup. Can this 600 VA UPS charge the 45Amps Battery?

    90. What is the value of the resistor on the Base its not clear R2

      Thank you

    91. Thanks very much! Going through all the comments I need to ask the question. Does this project actually work. The diagram makes sense as does the explanation. But alot of the negative comments worry me.

    92. Sir i need SMPS circuit having 18V and 6A output with 230V 50Hz AC input. Also no variation in milli or micro volts. Plz reply as soon as possible.

    93. hello sir..i want to ask for this circuit..if i use solar panel 12v 5watt-10watt, is it appropriate for this circuit???

    94. This is a bad charger. If you terminate the charging when the battery reaches 13.6 volts you have built a trickle charger. With this fixed 13.6v charger, after a short initial inrush, the current will reduce to a very low trickle charge rate and the battery will take forever to charge. It will also never get to 100% charge.
      A real high current charger will have a CONSTANT CURRENT output and should auto change to trickle charge when the terminal voltage reaches 14.4v (12v battery) A fully charged battery will have a terminal voltage of about 12.6v. This can only be measured about an hour after taking it off charge. It is NOT 13.5v as stated. If you take a battery off charge and immediately check its voltage it WILL be around 13.5v due to the surface charge. This will slowly settle back to 12.6v IF it is fully charged.

      Search the internet for better circuits.

    95. Hello sir, i made the circuit but i got 19v output when using 15v transformer and 15v output when i use 12v transformer, VR is not decreasing output voltage, i check check 3 time, i think i made it correctly , plz help me

    96. is this concept works on charging a 48V battery bank by proper sizing of those components?

    97. sir i want to add LED in d diagram so that it will tell me if the charger is charging. Where should i place the LED? I already made the circuit but i only got 13 volts how can i increase the voltage? I already adjust the vr.

    98. A good project sir. Please sir, can this charger charges a 100amps battery, and how long will it take to give a full? Tnx

    99. Hello Sir, What adjustment can be made with the obove circuit for the charger to be able to charge a 24 Volts, 8 battery (200ah battery connected in series).

    100. sir ,
      I have connected two 12v 7.2ah battery in parallel so do I need to do any changes in above diagram?

      please reply on my email . waiting for your reply …!

    101. sir,can i use 10 ampere transformer for this circuit??..what modification should i change the diode,my battery is 70AH..how many hours or minutes it will fully charge??

    102. Hello sir my self is asif i am working in nbst ibdustry and i want to develop a circuit based upon inverter and ups so i want to contact u personnely. Pls send ur contact details to my mail sir (shaikasif208@gmail.com) hope that u will cobtact me
      Thank u sir … i will be waiting for ur repply sir

    103. S.M.Waseemuddin says: on March 8, 2015 at 12:32 am

      sir please upload the “Fast Charger with Cut Off Circuit ” circuit diagram print for PCB tracing , or email me.

      I will waiting your prompt response sir.

      thank you.

    104. Hi sir,
      I’m anilkumar
      From TS
      My doubt can we add this ckt to 12 v solar panel.

    105. great article. i want circuit that combine fast and slow charge, whereby the user can switch between the two. thanks.

    106. Hello sir,
      I need to knows some thing from you.
      I have a 18-0-18 transformer. I want to use it on
      this ckt. How Can I do it (mens how can I convart
      it’s voltage in 15v?)
      one more, On the ckt I can see use 2 registance
      10 ohm 10 watt in parallel (it’s mens maybe, 5
      ohm 20 watt). Can I use another resistance in
      this place?
      What about the lag 1, 7, 8 of IC 555 and relaly’s
      upper lag? It’s not will be use on this ckt?
      please give me solution, it’s urgent… I will waiting
      for you.
      Best Regards,

    107. ohhh… sorry.. there is no 10 ohm 10 w capacitor… :)

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