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    Here is a solar charger circuit that is used to charge Lead Acid or Ni-Cd batteries using the solar energy power. The circuit harvests solar energy to charge a 6 volt 4.5 Ah rechargeable battery for various applications. The charger has voltage and current regulation and over voltage cut-off facilities.

    The circuit uses a 12 volt solar panel and a variable voltage regulator IC LM 317.
    The solar panel consists of solar cells each rated at 1.2 volts.
    12 volt DC is available from the panel to charge the battery. Charging current passes through D1 to the voltage regulator IC LM 317. By adjusting its Adjust pin, output voltage and current can be regulated.

    Schematic of the Solar Charger Circuit

    solar charger circuit schematic

    Solar charger with current regulation and cut off.

    video presentation of the working circuit with a 6V battery

    VR is placed between the adjust pin and ground to provide an output voltage of 9 volts to the battery. Resistor R3 Restrict the charging current and diode D2 prevents discharge of current from the battery.

    Transistor T1 and Zener diode ZD act as a cut off switch when the battery is full. Normally T1 is off and battery gets charging current. When the terminal voltage of the battery rises above 6.8 volts, Zener conducts and provides base current to T1. It then turns on grounding the output of LM317 to stop charging.

    attentionThe author D Mohankumar is not an active member anymore. Please take into consideration that the presented information might not be correct.
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    363 Responses to "Solar Charger for 6V Battery"

    1. Please….send to me a solar charger…output 12V/4Ah
      secuit schematic

    2. You can use the same circuit in the post by replacing ZD with a 12 Volt Zener

      • d mohan can i use this circuit diagram to charge a laptop? and can i add a voltage divider in this circuit a 16,19 and 21 volts output? can you help me

      • Johann Uys says: on December 2, 2011 at 1:53 pm


        I want to use it to charge 3.6v Lith-Iron battery but can not get it to switch of at required voltage of 3.6 volt.

        I am using 12v input voltage.



      • Johann Uys says: on December 2, 2011 at 2:39 pm

        Also not possible to start the unit up with a battery with say 2 volts

        Please help


      • plz reply how make inverter 200va-300va

      • Dear sir,
        i am thinking about a project to make a virtual aquarium in which fishes move by an electro-magnetic field, could u plz help me to design a circuit?

      • Dear sir,
        I would like to know how can i use wind energy to charge a li-iorn battery during travel. Is there any possibility to replace the solar cell with a small fan and a generator, could u plz reply me to mallotusphilipensis@gmail.com, am looking forward

      • dear sir i got only 7.63 voltage out put.if i bypass R3 then any problem?

      • Greatmultimedia says: on September 15, 2012 at 4:52 pm

        I am also facing same problem. Battery is not getting charged. Did you got any solution?

      • I am close to posting a 6V LDO Solar Charger that should solve your problem. Hope all works as expected. Keep watching the home page for this new circuit.

      • David E. Chigozie says: on July 19, 2013 at 4:40 pm

        we are waiting sir.

      • please i have some problem facing heare

      • chandrashekar.g says: on December 22, 2014 at 4:02 pm

        Dear sir,

        plase send LDO solar charger pcb lay out.

      • i am building a mini wind turbine for my senior project motor out put is 14. 3 volts and 3.73 amps, so my question is can i use this circuit to charge a 12 volts car battery

      • This circuit is very useful, I have not found any other shut down that do not use relay or dedicated chip, Thank you !

        I am concerned by the life time of my batteries: can you tell how to adjust the max current with this circuit ?

        Kind Regards

      • My 18V mobile charger Solar panel used to charge when the sun is present. but now it is not working when I try to charge it in USB. For your details info. My solar panel is 18V/40mA, LM7805 Voltage regulator and in USB.

        Thank you for your help.


      • sir..only replacing ZD with a 12 volt zener to charge 12 v battery ??? how about the other component ?? did not influence the output voltage ??? plz help me sir…

      • Hi Mr. Kumar.. can i use this “Solar Charger for 6V 4.5Ah Battery” to charge a 6V4AH? Thank you very much.

      • can you pls tell me the time taken for ther battery to get fully charged.(6.5v battery, 6V pannel(0.028mA))

      • i was wondering if the circuit worked to charge a lithium ion battery at 3.6v ??

      • CLP Raju says: on March 24, 2014 at 4:11 pm

        Hi Sir,
        I have 12 volt 10 watt solar panel, I need output of 6 volt 9 AH to charge my batteries (which 6 volt – 4.5 AH are connected in parallel), please suggest & help.

        C.L.P Raju

      • subbareddy says: on April 9, 2014 at 10:23 am

        i am facing problem in my 2w/6vsolar lantern circuit, when we switch on the light red is blinking for two sec and after that its fine. but red should blink only when battery is low. but if i switch on the light red is blinking fro two sec,its due to the existence of relay, i dont know how to compensate that the time delay? i am using 15k1/4,330e 1/4w ,resistors,

      • how about 100 ah can be used this circuit thanks for advance reply

      • I have to charge li-ion 1.1Ah battery using samsung charger 5volt/550mA. is it required any resistance in between battery & chargher to protect the battery? please tell me…

      • Dear sir,

        i have 3.7volt li-ion battery. i want to charge with samsung charger(5v/0.550mA) i want to design cutoff circuitry. do you have any cutoff circuit. my battery pick voltage is 4.2volt but i want to cutoff on 4volt or 4.1volt.
        please give me suggestion.

      • piyush patel says: on January 12, 2015 at 1:30 pm

        Dear sir,

        i making 12v/12ah battery charger with auto cutoff (14.4v) using 1.5a transformer Please suggestion and send me the circuit

        thanking you in advance

      • Dr. Mohammad

        can I replace the battery w/ 15W Dual USB Power Adapter Converter Car Charger For Battery charger then use the charged battery feed an Arduino Board.

      • সাইদুল ইসলাম says: on April 5, 2015 at 3:31 pm

        pleased give me same circuit input solar 12v to out put dc 6v 4.5amp…….

      • Jim Keith says: on April 5, 2015 at 5:00 pm

        Check out the following circuits:



        Note that with the shunt regulator, the solar panel voltage may be substantially higher than the battery because when the solar panel is loaded beyond its current capacity, the voltage drops substantially –and this is acceptable operation due to the high source resistance of the solar panel.

        A switch based solar regulator may also function OK, but I have not checked it for that.

        When using a 12V nominal panel (18V open circuit) to charge a 6V battery via a series regulator, the the power in the pass transistor increases substantially when the battery is topping off –to reduce this power, a power resistor may be added in series with the solar panel –design for about a 4V drop across this resistor. e.g. A 10A short circuit solar panel requires about a 0.4Ω resistor.

      • Dear sir
        Actually i have the following solar panel specification
        please tell me what is the modification that i have to do to charge the battery of 6V or 12 volts Lead Acid .
        Solar penal Specification
        Vmp =8.86
        Voc = 10.72V
        Imp= 0.35A
        Isc =0.38A

    3. D Mohan Kumar — I am also looking to use this with an output of 12 volts. I used a 12 volt Zener, however, i’m still getting only 6.9 volts with 12volts input. I checked and the output leg of the 317 is reading 7 volts. Are you sure this should work? Do we need to change the 317 to something else?

    4. This may be due to the input voltage. Usually zener requires 2 volts higher than its breakdown point. If it possible, increase the input using 16 volt solar cell. Also adjust VR correctly to control the output voltage. As a test, remove solar cell and connect 14 volt power supply. If output is OK, then the problem is with the solar cell. The output of solar cell will not be steady. That is why I designed the circuit for 6 volts using 12 volt solar cell

      • Dear, I’m looking for solarcell powered (3S)lipo charging circuit. do this work as it is or you suggest another for “lipo” as there are 3 cells in series?

      • sir my input voltage is 18v dcbut still out put volatage not more than 7.63 v DC

      • Hi Manideep,

        You can adjust your output voltage by replacing your ZD (zener diode) to 12V and adjusting the VR(variable resistor)until your output voltage increase to 12V, the variable resistor is connected at adj pin of LM317. Hope this will help to your problem.

    5. I want to assemble a solar powered 8 LED light box with light sensor circuit.I have currently assembled a 4 LED with4vdc 60mA solar panel and a charge circuit.This Circuit is charching 3 AA 1.2v 2.100mAh Batteries.Will I have to built another charge circuit for more batteries and 8 LED’s

    6. Can you please assist me with a circuit diagram.

    7. Charge circuit at present consumption: 2.5mA (standby in sensor mode) 80mA (working in sensor mode)

    8. There are solar charger circuits in the same site.Click on my name and see the postings

      • hi sir im a biomedical enginnear i wana make a solar circuit myself so help me plz im from pakistan karachi

      • hello dear
        I’m looking for 6/12volts 10/55A ENGINE CHARGER STARTER .
        BEST REGARDS .

    9. please construct to me the circuit of 12v dc servo motor and how to control the speed,heat sensor circuit and solar charger circuit.i need immediately before end of this month.

    10. What if I have different component ratings? How should I customize my circuit? Since I am using a 7.5 V solar panel, 6V battery 4 Ah. What is the optimum values of components? Thank you.

    11. You will not get sufficient voltage from a 7.5 volt panel to charge 6 volt battery.Use 12 volt panel.The components remain same

      • robertk445 says: on June 4, 2013 at 10:05 pm

        Sir I need to charge a 3.7V lithium Ion OR 3AA rechargables at 3.6V .
        What is the best size panel voltage to use? I am looking at 5V solar panel that will produce between 2-3 Watts
        I am building solar project which requires ability to power 1meter of rolled leds. The Led are rated at 4.5V 60led/meter
        at 2 W I can charge 2000mA per day. My usage would be 1256mA =62% draw
        at 2.5W I can charge 2500mA per day. My usage should be with 1 full meter .157A
        157mA * 8 hours =1256mA 50% draw

        can you please help me with a circuit board design to meet these requirements: charge by day, light by night, cutoff charger at 3.8V.
        and anything else I am forgetting.
        Thanks you so much!!!

    12. Heat sensor and solar charger circuits are in electroschematics.com.Search by name.Servo motor circuit will be posted soon

      • Dear Mr. Mohankumar
        Actually i have the following solar panel specification
        please tell me what is the modification that i have to do to charge the battery of 12 volts Lead Acid .
        Solar penal Specification
        Vmp =9v.
        Voc = 10.8V
        Imp= 0.33A
        Isc =0.36A

    13. i have project which is automatic vehicle wiper..when heat sensor detact the heat,the heat give signal to servo motor to rotate..then,in case if the batteries didn’t not have to much volt to make servo rotate,so i’m use solar cells circuit to support volt and ensure the wiper up…can Dr. please give help me to provide circuit?thaank for yout cooperation

      • Dear Mohankumar
        Actually i have the following solar penal specification
        please tell me what is the modification that i have to do to charge the battery of 12 volts Lead Acid .
        Solar Specification
        Vmp =9v.
        Voc = 10.8V
        Imp= 0.33A
        Isc =0.36A

    14. richard solway says: on March 15, 2010 at 9:21 pm

      how about a blocking diode to prevent discharge during darkness.

    15. richard solway says: on March 15, 2010 at 9:26 pm

      whoops my bad. i coughed and missed the bit about d2. d’oh. keep up the good work.

    16. i have solar pannel and output of this is 10v.how can i use it for making mobile charger????

    17. See the posting Solar based Multipurpose Charger.Mobile charger is included in it. Use that part only with 10V solar panel

      • good day Mr. D. Mohan Kumar, for this circuit diagram, can i have the component ratings so as to purchase online. I’m new to this field, please pardon my question. ie, i dont know what is LM317 and VR1K.

        my panel is 43Watts [Isc 3.3Ampere & Voc 18Volt] and battery is rated 12Volt, 17Ampere-hour, is it applicable for this circuit?

        could you please email me @ polt525@yahoo.com

        thanks & regards,

    18. NISHANTH CHENNAPPA says: on April 17, 2010 at 7:14 pm

      SIR i want a battery charging circuit for 10w solar panel which is having a variable out put voltage from solar panel(input to battery charging circuit is ) 5v-24v to charge a battery i need a circuit design which gives a constant output voltage 15v(output from battery charging circuit) could u please mail the circuit to nishanthsjbit@gmail.com

    19. sir,
      i am so impressed by your projects, thanks for devoting your precious time.

      I want to make a solar powered light, how do i get a solar panel in India, is there any online shop which can provide the panel.

      Also it would be of great benefits to new visitors if you mention the price of solar panel on your site itself.

      Thanks again for your great work.

    20. Ready made Solar panels are available in India. Its cost may range between Rs.800 for 6V 3W panel to Rs. 2800 for 12V 10 W panel. Visit the website of Gala electronics,Mumbai. Catalog can be down loaded

      • manu_alld says: on May 14, 2010 at 1:54 am

        Thanks Dr.Mohan, I found the site
        vegaitindia.com and i remember i used to learn thru their kits about 20 years back.

        thanks again

      • Prasanth Nair says: on November 26, 2011 at 8:34 am

        Dear sir,
        Ready made Solar Panels of 2W & 6W 6Volts are available in espareonline.com
        Price is 350.00& 399 Rs only

        Prasanth Nair

      • I want your email to Arusselk
        Iam student for m.sc in the iraq for the solar cell

        can you help me if Asked/you
        if you can send the replay to my mail

    21. NISHANTH CHENNAPPA says: on May 23, 2010 at 1:26 pm

      sir in the given above circuit will not indicate the over charge of the battery. due to this after the complete charge of a battery, the battery will be still charging. this will affect the life of the battery. is there any comparator circuit that indicates the over charge and stops charging the battery. if there is low battery starts charging automatically.

    22. I have posted some charger circuits with cut off facility.You may go through the postings.I will post a circuit using comparator soon

      • bala selvam says: on March 10, 2012 at 7:18 pm

        Respective sir i’m doing IInd year EEE … i’ve so much interested in projects … and i have started one … in that a 12v 5w solar panel is giving the supply… can i use any other source instead of that of the same power

    23. hello sir….i m ankit from India…can u plz mail me all circuits which u have…actualy i have a great interest in electronics…and wsnt to do inventions…so i request u all to mail me circuits with theory u have….
      Plz mail me circuits and programming based projects also….plz keep on forwarding me as u get new updates on Electronics…it can be any….thnx….

    24. Hi, thanks for sharing this circuit! I have built it, but I’m not sure how to test it. When I connect a multimeter across the place where the batteries should be, the reading is in mV. Is that normal? And is it ok if I use NiMH batteries instead of NiCD batteries?

    25. Measure the output voltage in 20 volt range of DMM after placing the solar panel in bright sunlight.NiMH battery needs proper monitoring. You can use the same

    26. Thank you so much for your reply Sir. If I set up an LED at T1 to blink when the battery is charged so that the user can remove the batteries, will that work? How do I set a 20 volt range for DMM?

    27. Hi Sir, i am currently working on a solar garden light project. I need a charge controller circuit to power some 6 LEDs of 20mA, 1.9V. Also i need to protect my battery from
      overcharge. Can this circuit meet all my requirements? If not what modifications can be done to meet my requirements?

      Thank You

      • pleas Dr Muhankumar i have 12 volt solar panels give 19 volt in sun shine and i wont to charge 6 volt battery can you advise me
        best regards

    28. Hi Mr. Mohan, I’m planning to use 2 solar cells to charge a 6V 4.5Ah Battery. Here I have 2 packages of solar cells,
      -(1) 2 pieces of 6V 100mA solar cells and
      -(2) 2 pieces of 0.2W 5V solar cells.

      Which package of solar cells would u recommend if I’m gonna use the above charger circuit? Any additional advice plz?

    29. technical know how for solar chargers circuits.solar panels solar led lamps

    30. dear sir,

      I am stuck at my final year project. I need a charging circuit to charge the 6V lead acid battery in our design. And this circuit is just fine for that. But the problem is that the solar pannel we have is just 6V. How can I change this circuit so that I can use the 6V solar panel instead of 12V solar panel?

    31. 6 volt solar panel is not sufficient to charge a 6 V battery since the voltage level depends on the intensity of sunlight.Try to construct the circuit and measure the voltage from the panel.If it is more than 6V, you can use it, then change the value of ZD to 4.7 volts

    32. i want to design solar mobile charger for my final year project ,i want you to put me through.
      i shall be grateful to see your favorable response.

    33. Hi! i am using an 18V solar panel to charge a 12V 1.2 Ah battery… what zener diode (ZD) should I use?

    34. Hello! what is the output current for this circuit (during charging time)?

    35. dear sir, we are doing the project on solar charge controller circuit.can we charge the lead acid battery of 12v by using the 12v,20watt solar panel with the solar charge controller circuit ,if possible what we have to change with the above diagram

    36. Hi,
      I don’t understand the purpose of T1,ZD and R2.
      LM317 itself can fix the o/p voltage to a particular value and you already have the register R3. Also as the battery is being charged from solar panel(assuming it low wattage as otherwise it will be an inefficient use for 4.5AH battery charging). I am charging a 7AH 12 volt battery with a solar panel and LM317(without the T1,ZD,R2)it works just fine.

    37. i would to make battery charger by using 3 input; AC,DC and Solar source….i need some advise from you guy….

    38. hi sir,
      I am impressed with your schematic diagram for solar charger.I want to know what I need to change in this circuit if i want to charge a 12 volt/1.2A rechargeable lead acid batter.

    39. I have another question.I am using three 6volts solar panel which has current of 0.1A each.Can it be used to charge a 12Volts 1.2Ah battery

    40. If i want to insert a LED Light in the circuit to indicate it is charging where is the best place for me to insert the light?

      • D.Mohankumar says: on November 16, 2010 at 5:35 am

        You can insert an LED with 1K series resistor at the output of LM317 before R1.Make sure that output is sufficient to drive the charging circuit and LED. LED takes 1.8 volts. If the output from LM317 is more than 10 volts, LED can be placed.

        If the solar panel is giving 18 volts(6×3), replace ZD with a 12 volt zener. All the components remain same.Usually zener requires 2 volts excess than its rated voltage to enter into breakdown state.

      • Dear Mohankumar Sir,
        The idea of placing a 1K series resistor before LED is to reduce the high current passing through the LED as most LED’s are rated less than 50mA right?

        If so then please explain what is the need of R3 at the output. Is the current already not reduced by placing the 1K resistor at the output?

    41. ok thanks sir.Can I at the same time connect any load the battery while charging.If yes how do i do it?

    42. well i would i like to connected a LM35 temperature circuit and also 2 servo motors rated 4.8V.Will it be possible?

    43. Possible if the battery is fully charged

    44. if i put two batteries in a serie it will be charge both of them?

    45. It is better to charge the batteries individually. If one battery is old, internal resistance of the battery will reduce the flow of current.

    46. Dear D.mohankumar,
      I’m interested in build your circuit. But i can only find 5.5 and 6.5 volt solar panel in my place. So, i’m trying to build it by using 5.5 or 6.5 volt solar panel and 3.6 baterry.If i want to change the solar panel into 6 , and 3.6 baterry, what should i change in the circuit??

    47. Dear Mr.William

      The circuit is designed for 12 volt panel. If 6 volt panel is used, there will not be sufficient output voltage from LM317. More over the circuit itself consume some power.So that sometimes the battery will not charge.An alternate way is to connect the solar panel directly to the battery through a IN 4007 diode. Observe polarity during connections.Diode will drop 0.6 volts.So that 5.4 volt will be available.3.6 volt battery requires more than 2 volt excess for steady charging.But auto cut off facility will not be available.

      • hello dear
        i’m looking for inside diagram of 55/10/2 ampere 12v engine starter and battery charger ciecuit.
        please help me
        best regards

    48. hi Mr. D.Mohankumar, may i know what is the use for the wire joining from junction below ADJ to the junction at between R1 and the collector of T1???

      • D.Mohankumar says: on November 20, 2010 at 5:22 pm

        Dear Mr.Baby
        The adjust pin of LM317 voltage regulator is used to adjust the output fro the device. In the circuit the Adj pin is connected to the collector of T1.As long as the terminal voltage of battery is below 6.8 volts, zener remains off to keep T1 off. When the battery voltage increases to 6.8 volts, zener breakdown and provides base current to T1 and it conducts. This pulls the adj pin to ground potential and drains the output to ground. This stops charging.

      • but then isn’t that the fully charged 6V Lead Acid Battery is 6.3V?
        will the voltage of battery raise to 6.8V?

    49. thx for replying my question before, but i have 1 question in my mind.
      How if i use this battery in this project to light a white led??

    50. i want to design solar mobile charger for my final year project ,i want you to put me through.
      i shall be grateful to see your favorable response.

    51. Sir i would be more than happy if you could assist me with this project i’m working on.the thing is i’m stuck and need your help.which solar panel do i need to carge 3V battery and how do i make the charging to automatically stop when the battery s full and charge again when its almost empty?pliz help…

      • D.Mohankumar says: on December 1, 2010 at 2:53 pm

        You can use this circuit with slight modifications.Use 12 volt 5 watt solar panel. Increase the value of VR to 4.7 K. You can adjust the output voltage through VR.Measure the voltage after D2 and adjust VR till it drops to 5 volts. Replace R3 with a value for required current at 5 volt using ohms law.Replace 6.8 volt zener with 3.1 volt zener.Experiment with the circuit and get result.

    52. hello
      you design for 6v battery what about the circuit for 12v battery

    53. hello
      you design for 6v battery what about for 12v battery

      • D.Mohankumar says: on December 11, 2010 at 9:03 am

        Use 18 or 20 volt Solar panel and increase the value of ZD to 12 volts. You can use it for 12 volt battery.

    54. hello
      please brief description why u use the above value of resistor and type of transistor

      • D.Mohankumar says: on December 12, 2010 at 2:51 pm

        Hello Rehima
        During a circuit design, usually the value of the resistor is determined based on the current passing.Ohms law will help to select the resistor. General purpose transistors are used depending on the current handling capacity

    55. Hi Sir
      Excuse my ignorance, but I seem to be misinterpreting something. If R3 is 10ohms and the charge voltage from the LM317 is 9V, then I assume the charge current is 0.9mA. I am confused as to the power rating of only 1W for R3? Please advise me as to where I am misinterpreting the circuit. Thank you for your patience.

      • D.Mohankumar says: on December 13, 2010 at 3:48 pm

        Dear Justin
        Suppose the output from LM317 is 9 volts. If the output current is above 1 Amps then 9/10 = 0.90 Amps. That is 0.90 x 1000 = 900 Milli Amperes.You can use 1W resistor as R3.

      • Justin James says: on December 13, 2010 at 4:44 pm

        Thank you for your response, I apologize, I did mean to say 0.9Amps and not 0.9mA. However I am still confused, I thought that the required power rating for the resistor had to take the 10ohms into account. I thought it came from P = I^2 * R = IV (0.9A)(9V) = 8.1W.

      • D.Mohankumar says: on December 13, 2010 at 5:10 pm

        Dear Justin

        1 Watt resistor can handle up to 1 Amps current

      • Justin James says: on December 13, 2010 at 5:25 pm

        Thank you very much for making that clear, I still have alot to learn!

        kind regards

      • Chinmoy Mitra says: on January 7, 2011 at 8:49 am

        Dear Sir, I beg to differ from your explanation. What Mr.Justim JAmes has writtten is absolutely correct. He has quoted Ohm’s law, and acording to that, the power dissipation in a resistor is dependent on the current squared multiplied by the VALUE of the resistor. Saying that “1 Watt resistor can handle up to 1 Amps current” does not make any sense electrically. For example, a current of 1 Amp will cause a power dissipation of 1 watt in 1 ohm, 10 watt in 10 ohm, 100 watts in 100 ohm etc. I hope this shall clear Mr. James’s doubt.

    56. Hi Sir, I am conducting a project for my leaving cert in school and I was wondering if you could help me. I want to have a model house with L.E.D. lights and switches, fake sockets and a fan which would be powered by a 9 volt battery. It would show different circuits, e.g. radial and ring circuits. It would also be interruption resistant. How could I use a set up like yours to charge the battery with a solar panel but stop it being overcharged? And also allow to L.E.D.’s , fan, etc be powered? Thanks very much for your time, I hope you can help me.

      • D.Mohankumar says: on December 13, 2010 at 5:18 pm

        Dear JK
        For simplicity use 2 circuits.Use the solar charger circuit for charging battery. Use the MINI EMERGENCY LIGHT posted in the site for automatic working of LEDs.In that circuit, a relay should be connected in the place of White LED. Remove the LED and series resistor and connect a 6 volt 100 ohms relay with IN4007 protecting diode. You can connect all the loads to the relay

    57. Hi Sir
      I have adjusted your circuit to charge a 3.7V battery, could you advise whether or not my changes are sufficient:
      R3 is 22 Ohm resistor
      ZD is 3.9 V zener
      LM317 is outputting 6 V
      using 1N4001 diodes

      thank you for your time

      • D.Mohankumar says: on December 14, 2010 at 6:04 pm

        Dear Sheldon

        Try your circuit. Value of R3 depends on your current requirements.All other parts OK

      • Hi Sir
        I tried the circuit, the LM317 output was 6V before connecting the 3.9 V zener and transistor switch(and 2.1 V after connection of zener and switch), then when I put a 3.7V cellphone battery that was running flat across the charge terminals, the circuit does not charge it. Would the zener rating have to be higher perhaps, because I know that cellphone batteries still read approximately 3.7V when your phone tells you that they are flat?
        Please advise, thank you.

      • D.Mohankumar says: on December 16, 2010 at 8:29 am

        Dear Sheldon

        Usually the zener requires 2 volts excess than its rated value to complete its breakdown. For example, if you use 3.9 volt zener, input should be around 6 volts. That part is OK. The problem is the charging voltage. Usually the rechargeable cells ( 1.2 volt) requires 2 volts per cell to accept charge. Mobile phone battery is rated 3.6 volts ( Three 1.2 volt cells in series). So minimum 5 volt is required to charge it. Use a 4.7 or 5 volt zener. The problem will be rectified

      • Hi Sir
        I thought that 4.7 V would overcharge the battery and be harmful? Also, could you advise where I could look to find information on charging 12V batteries with high AH ratings, through a 75W panel that has optimum of 17,5V and 4.29A operating conditions? Is there a voltage regulator and transistor combination I could use in this circuit to achieve and handle the approximately 4A of current for this, as I understand the LM317 can only output 1,5A?
        Thank you very much for all your help and advise.

    58. Dear Sheldon
      This circuit cannot be used for high current charging. For that search for solar charger circuits in the front page of this site.I have posted some circuits. The charging current is minimum irrespective of the battery AH. See, the charger of inverter with 150 Ah battery uses 15 volt and 2 amps current. Usually during the initial stage, battery consumes around 1-2 amps current which drops to 500 ma or less during the remaining hours.

    59. for 12v battery charger what would be the value of resistor on the previous value i checked the circuit but does not work and how to calculate the power and the current

    60. Sir,
      We want to charge a 12V 7 Ah battery through a 12V 5W solar panel. We have a two step PWM charge controller. Can you please provide a simple but a very reliable circuit with the following specifications:
      1. One green indicator should light up when the battery is charging
      2. If the battery voltage drops to 11V (off load / on load) then red indicator should light up along with a beeper
      3. If the voltage drops below 10V then the output should go on and off continuously with one second gap
      Thanks and regards,

      • D.Mohankumar says: on December 21, 2010 at 2:33 pm

        Dear Kumar
        I will post a circuit you mentioned. To charge a 12 volt battery, an 18 or 20 volt panel is necessary to give steady input voltage. Since the current in the panel depends on the incident light, a higher value panel is preferred.

      • Thanks Mr.Mohan for the quickie. The panels are giving about 18 to 21V even in moderate light. So the probability of chances to satisfy your requirement is quite high. Also the charge controller is designed for handling input voltage from 9V to 22V with a steady output of 14.4V the charge the battery.

      • D.Mohankumar says: on December 21, 2010 at 2:52 pm

        Dear Kumar

        What is purpose of on/off the output continuously when the voltage drops below 10 V.Is the output current to battery, or the beeper circuit.What is the use of PWM in low voltage level.Please clarify. First two parts are easy.

      • Dear Mohan,
        The purpose of on/off of the load (here LED light) is to warn that the battery is going deep discharge and the load is to be disconnected ASAP. In fact a relay should be better but in most times it will totally disturb the work especially if the work is under completion. Here the output to load is to be made with this arrangement. The PWM may not be useful in low voltage level but being a two step PWM the boosting and bucking nature was found to be more advantageous.

      • Dear Mr Mohan, Hope you remember the discussion. I am very much in need of the circuit which provides a low voltage indication @ 11.5 WITH OR WITHOUT the load.
        Hope you will provide a solution soon.

      • dear mr muhn kumar
        i have 18 volt solar panels 5 watt i wont to charge battery 12 volt 7 ah for one day and i used it at night for led light do i need charger controler and why and i think their is some calculation with solar power and battery cabacity to prevent over charging pleas can you advice me
        thanks allot
        best regard sam

    61. Sir,
      I have adjusted your circuit for 3.7V battery . Does the value of R1,R2 and transistor T1 remain same?

    62. sir , i am 2nd year student and i want to make this circuit. can i?

    63. Hi

      I am designing a solart panel jacket where I can charge mobile phone,mp3 etc. I am using 3.6v 100 ma solar cells. I don’t know what sort of circuit diagram I will need.
      Can you help me please.

      Thank you very much.

    64. Sir I want to make a charger circuit that will charge a 3.6 V battery of mobile phone. To do that we need 5V and 350mA output of charger circuit. On the other hand I have a 12V 10W solar panel that I will use .

      Can I implicate this circuit ? What change is needed? I am thinking some , but there are some key problem .
      Rз is 17 Ω resistor.
      As my current is 350 mA , can I use .5 watt resistor?
      What will be the ZN ? 3.9 V or 5 V? and why?
      Is diode 1N4007 or 1N4001 and why?
      What about VR to get 6V out put

    65. hi sir,
      if i use four 1.2V rechargeable battery in series on the battery holder, izzit can work???

    66. hi sir,
      why is the value of zener diode 6.8V?
      since the total voltage of battery is 6V?

    67. hello sir,iam sasikala DC signal is high frequence or not.pls response me sir.then what i8s AC and DC signal.

      • s.h.reddy says: on July 4, 2011 at 11:56 pm

        Hallo sasikala.
        Flow of electrons is called electrical current.
        If an electrical current flows only one direction from source say battery to the load say a bulb it is called DC current.and the frequency is Zero hertz.
        if an electrical current flows first in one direction and reverses its direction in the next moment say in one second time it is called AC,and and frequency !htz/sec and if the direction reverses 50 times in one sec then the frequency 50 htz,if the direction reverses 1000 times in one second then the frequency 1khtz

    68. Hello Sasikala
      Are you asking the general property of DC /AC. Please give in detail

      • Dhananjay says: on May 14, 2012 at 10:21 am

        Dear Sir
        Can I use this circuit for solar panel of 17 v & 11 watt & for 12 v with 7 Ah battery. what changes need to do in the ckt. please help.

    69. sir i have 2 watt solar panel.i want a solar charge controller circuit for it.

    70. Sir I implemented the circuit but it does not work or can not able to recharge mobile phone. On the other hand it terminated my mobile phone………….how funny your circuit is !

    71. sir, can i connect a load to the battery? if yes how do i connect it? thank you for your time sir..

    72. hello
      i have problem in calculating time to charge battery by solar pannel battrey of 12v and solar pannel of 120wp.what should be the vaule vr , zd and r1 in above circuit

    73. hello
      i am preparing a solar helmet .my requirement is for a flexible solar panel.i am searching for a flexible panel supplier from last few weeks but i am unable to get it.can you suggest me if there is some one who can provide me with 6V,5W or 6V,3W solar panel.

    74. Hai sir , can i use this circuit to charge lipo battery , 7.4v and 1300mAH safely.

    75. yes,,, nooo,,, i like this

    76. Sir

      How can i make a 19V 2.1A output with this same circuit for my laptop. Please help me

    77. Hi

      I am making a solar panel circuit in order to charge mobile phone and Ipods. I don’t know wheather a lm 317 voltage regulator is acceptable. my desired uotput voltage is 5v. I am using two panels which produce 8.6 volt. Please help.


    78. hello sir

      i builded this circuit on a general board
      the voltage across R3 is 9.46V but the battery is still not charging
      can u please tell me the current required to charge ??
      the battery i am using is lead-acid battery with 6v 5Ah rating

      please help me out sir

      and last question

      current produced by my solar panel is 100mA is that enough ??

      thanks in advance

    79. i have battery of 3.7v,1200mAh,4.5wh…so how to arrange it.plz tell me

    80. raviteja, your current is too low. Normally u need 5A x 10% = 500mA to charge your battery, and this 500mA current might take around 10hours+ to fully charge your battery, imagine how low is 100mA.

      fazle, if your battery is 3.7v, i not sure what is the fully charge voltage,i assume is 4V. So u need to adjust the output voltage to become higher than 4V + 0.7V(diode) = > 4.7V. I assume is 5V.

      By using the LM317 formula, Vout = 1.25(1 + R2/R1), so u just adjust the VR will do

      If your fully charged battery is 4v, then put a zener diode which is 3.9V standard value.
      1W,3.9V zener diode will be 1N4730

    81. Hi Sir!
      Good day to you. I already build the circuit. The output is in milivolt. Actually i need to charge 4 NiMH AA batteries with 20V 1A solar panel. Could you assist me to build the circuit. Another one is that, i need to know the battery arrangement in order to make the battery equally be charged. If possible, could you email me.

    82. Though its simple ,LM317 is used as series Regulator and the effeciency of the circuit is very very low.instead switching regulator can be used where the power wastage is minimum and so the effeciency is increased to 80 to 85%.

    83. can you please mail me how to do a solar charging circuit for a 9v battery which is used drive 2 dc motors….

    84. sir,please help me in making my project.A battery charger with an input of 220volts ac and an output of 10 volts dc,1.3 amp.

    85. richesh bhargava says: on May 16, 2011 at 12:29 pm

      hello sir i want lay out of solar charger circuit of o/p 6v

    86. hello sir .my project is solar based mobile charger , i have a problem with while charing the mobile “bad contact of charger” is occured. iam using 6v ,150mill amps solar panel . what is the problem and give the circuit for this.

    87. I have what is perhaps a stupid question. I bought a 2 feet by 1 foot solar panel (I think it is rated at 15 watts / 1 Amp) which is marketed as a 12V kit(Sunforce 50033 15-Watt Solar Charging Kit). I put the output of the solar panel into a cig lighter female jack, and plugged my car cell phone charge into this jack. This worked fine – the open circuit DC voltage was like 19 Volts but dropped down to 10-12 Volts when charging @ about 1 – 3 watts of power – most of the time. I then used the solar panel to charge a deep cycle marine battery (using a charge controller). Then things started to go haywire.

      First) After charging the 12 V Deep Cycle battery for a while, I connect the cell phone charger to the battery and heard a ‘pop’. Is this a no – no? I was assuming it would work since the cell charger works in the car.

      Second) I bought a couple of extra car cell chargers for use with just the solar panel (Not the marine battery anymore) since it appears to fry things . Charging then through the solar panel seems to break them after a while, though the fuses don’t blow and the light on the charger remains lit, plus, the cell phone still charges when connected to a wall jack. I have noticed that the voltage sometimes goes up to 14 or 15 volts when charging the cell phone. Is this too high? Is this caused when the cell phone is almost charged and is not drawing much current? Could this be breaking something in the charger?

      Thank you in advance if you take the time to try and answer any part of this question. I am just starting to gain practical knowledge working with solar and will do my best to pass on any wisdom I gain.

      Best Regards,


    88. hellow sir,what are the stepes i can follow to charge my (8 eight) 12V battery connected in siries.

    89. hellow sir,i am praveena i had done this mini project of charging the Nicd battery it is successfuly working but i have to give a demo on 20th of july and i dont understand the proper function of resistor R3 and diode D2 please give me the complete explanation of it .

    90. Hello, sir am looking for a circuit which enables the battery only yo be charged if the voltage from the solar is high exp, in the range of 13 to 18 only… at the same time the circuit including to stop and start charging of battery when its full…

    91. I want to design a solar charger. please give circuit diagram for 5v, 10v,18.5v , 19v, 20v. thanks

    92. Please send me a circuit diagram of dynastarter

    93. hello sir,
      i need 12v1a solar to 12v12amH battery chcher cuir cuit
      please help me

    94. hello sir, i want to make a mobile charger. can i use this circuit provided that i change the input voltage to 6V and the zener diode to 4.7v? i will leave the other components the same. Is that possible?

    95. hello sir,its my first time in posting something here,so my question is:could use this circuit to charge Li-ion batteries???
      ill wait for ur reply…

    96. Dear Sir i want course module of 45 days training on Mini Solar lamp Assembling,latten , kindliy suggest me where i can get raw material in cheaper price. This project is very much important for the poor people in orissa which can help them. waiying for kind reply

    97. sir,
      i bought a solar panel (6v 200ma) and i would like to charge the 3v 1600maH.
      so pls suggest me to do any modification in your circuit….
      thanks in advance

    98. can u pls mail me a 6V solar mobile charger circuit.??

    99. Please, D. Mohankumar, you can use this circuit to charge a Lithium battery 3.7V and 2.400mAh?
      Thank you very much
      José Vieira
      Aparecida, São Paulo, Brasil

    100. Dear Mr. Mohankumar:

      I would like to build a charger that basically would charge one or two nine volt rechargeable batteries by ten volt solar panel(s).

      Would it be more efficient to use switching regulators instead? What solar panels should I use to provide adequate charging current for charging?
      Do I have to select such panels with maximum short circuit currents? By what percentage from the solar panels´ short circuit currents shall I be able to utilize the most efficient charging currents from the solar panelS?

      I await for your reply!


      Joe L. Siklosi

    101. Hi.
      I want to use this charger for a 6 Volt lead acid 1.2 AH.
      Please help me for change.
      Thank you.

    102. Hi again and 1 more question.
      Would you please help to use a LED showing in charg mode?

    103. Thanks a lot mohan sir i have constructed your solar panel circuit and its working great …. !!!!! Thanks A LOT

    104. Thanks a lot mohan sir i have constructed your solar panel circuit using 6v solar panel and its working great …. !!!!! Presently I am using That power to my mini speakers …. !!!
      Thanks A LOT


    106. Hello…

      Thanks for the article. Could it work for lower input voltages (6V instead of 12)and output of 2-5V by changing the zener diode to 2-5V?

      King regards

      • Well i tried using a 6v solar panel and it was working great …. !! I think the zener diode used as a cut off …. !! for me i dint require a cut off .. just to complete the circuit i used a zener diode

    107. Please help, I have a 14V solar panel,It was working before, but the diodes inside burnt, and now it does not charge the battery,but I can watch a tv and drive a 12v-240 inverter using it,but it cannot charge the battery.

      does it mean that if I use this circuit it will charge the because it still provide 14v but it can not charge the battery.

      please help.

    108. tell me the cost of total project of solar charger circuit.and also tell me the i am working in 200w so there it not working. pls give me the ckt diagram of load 200w and price list

    109. sir I want to design a 12 V solar charger. please give circuit diagram for , my solar panel is 40 w and 17 v

    110. Sir, I have two solar panel one is of 16V and other one of 21 volt output. I want both the panel to boost up charging current. so please tell me, if any modification is required in your ckt diagram. I want to redesigned the ckt to charge 12V and 80 to 100AH battery. Thank you

      • Udhaya Raj says: on September 14, 2011 at 6:36 pm

        Hello shasi,
        you asked about boosting up the charging current right okay fine…
        i think i can help you in this
        can u please answer my question?
        1.current rating of both solar panels ?
        2.correct battery AH?
        3.type of battery?
        i mean (lithium cell or ni-cd cell or lead acid cell)

      • Thank you for your reply. My solar panels are of 50W each, battery is of lead acid cell 150Ah.

      • Udhaya Raj says: on September 15, 2011 at 8:17 pm

        hello shasi,
        the battery you mentioned here is 12V 150Ah.
        then it takes 10Hrs to charge when supplied with 15A…
        and your solar pannel can’t deliver that much of High amps.

        so there’s only two way
        1.reduce your battery Ah
        2.You must add solar pannels to attain your battery current

      • is there any changes required to make in the given ckt.

      • ya many more changes required…. bcoz the current you needed is quite high

      • ya shasi….
        many changes needed,
        and that is for smaller rating with less current.

        but you are aiming for high current….

      • Can you please send me the modified ckt to my mail id or share to this website. Thank you

      • udhaya raj says: on September 17, 2011 at 7:33 pm

        Without knowing the solar current battery rating and some more calculation are there,
        without knowing those thing you can’t design a circuit or modify the circuit ….

        Itz like a blind watching a cinema so if you ready to give the specific rating i sure i can help you if not i’m sorry i can’t

      • Solar panel rating: 3nos of 17V, 200W.
        Battery: 12V, 150AH.

    111. Hi Sir,
      For the above original circuit, as it had been mentioned above, the output of regulator is set to 9V. And the breakdown voltage of zener diode is 6.8 volt. So, wouldn’t the zener diode already allow the reverse current even before it start charging.

      Please help me understand the circuit. Thank you.

    112. what is the price of 12v solar palan in kolkata

    113. pls give me a circuit diagram and working of fire alarms using solar panel.

    114. I ask everyone: You can use 7815 instead of the LM317 in this circuit? Thank you.

    115. what is the cost of solar panel in this circuit?sir

    116. do you have solar charge controller circuit?

    117. Dear Sir, thanks for answering our questions. Please, i need your help. I built this circuit but is not working as expected. My transistor is conducting even when I have no battery that is being charged.Considering the the charging voltage which is 9V, its greater than 6.8V and should actually turn on the base of the transistor. If ZD is going to conduct when the battery that is being charged gets above 6.8, why shouldn’t 9V conduct. I may be wrong. thanks.

    118. Dear sir,
      kindly suggest me a circuit to build a solar charger for study lamp in which i wants to glow 4-8 LED’s for 3-4hrs what should be the rating of all equipments so that i can do the same. also a circuit.
      thank you

    119. i need circuit diagram for solar car using PIC..can u help me sir

    120. Dear Mohankumar,
      I have a 2v solar panel and a 12v 100Ah Deep Cycle battery. What type of Charge controller should i make to constantly charge the battery? I want to use the battery for operating LED lights in my house.Can you kindly give me a circuit diagram so that i can make my own Charge Controller? Thanks in advance.

    121. Dear sir;

      what can i add to this circuit to make it great because im using it fot the final project and i changed the circuit to make it better but i need to add more like another circuit(i need help) .

    122. dear mohan kumar
      i need solar mobile charger using 3-4 volt solar pannel. can u help me………./

    123. hi Guys

      I am new to this and trying to charge 5 x 1.2 volt batteries whilst running a 6 volt motor at the same time, but cannot get the batteries to run at the same time. So what it is the panels run the motor whilst charging the batteries and when the sun dissapears it runs the motor from the batteries.

      Does anybody have a schematic i can use for this… I will be greatly appreciated.

    124. Please….send to me a solar charger…output 12V/80Ah …. voltage from solar panel(input to battery charging circuit is ) 75v to charge a battery i need ….. to find information on charging 12V batteries with high AH ratings, through a 75W panel

    125. Hi

      Could you advise me what to change in the circuit for a solar panel of 6v, charging a lead/acid of 4v

      Many Thanks


      • hi
        i would also like to know what changes are needed to have a 6v solar panel and a 4v battery.
        also if used 6v solar panel and 6v battery what would change.

    126. Sir,i want to make solar home light system.in which 3 watt led bulb 3nos and one fan can work. Please suggest me about panel,charge controler,batteryand also tell me the circuit of making 3watt led bulb.

    127. Hi. I have a game camera that operates on 6 volts. I have installed a 6 volt rechargable battery to power the camera and a solar panel that has a power rating of 0.63 W and a charging voltage of 9.0 volts. The camera takes about 40 pictures weekly and the battery seems to hold a charge for a week or so but the charger seems to not be trickle charging the battery. I have installed the same setup on a feeder that operates two times daily and the battery is always 100%. If I build this circuit, will it work to maintain the camera fully like the feeder?

    128. D Mohan Kumar – Please, can i use batteries Li-Ion (Lithium) 3.7V to load in this circuit? Thank you.

    129. Dear Sir,
      Can we use the circuit for charging of 4V 4.5 Ah SMF battery which is commonly used in Led Lanterns (3.6V 3W led)
      If possible what changes to be made
      Please reply
      Prasanth Nair

    130. Sir

      I can not start it up with a reasonably flat battery- 2.0 volt.

      Please help



    131. at how many amps will be the charge? what will I do to change the charging current? change the value of R1?


    132. Please, this circuit can use Lithium?
      Thanks to all

    133. hi sir,
      I am impressed with your schematic diagram for solar charger.I want to know what I need to change in this circuit if i want to charge a 12 volt/1.2A rechargeable lead acid batter.

    134. Hi sir,
      please tell me the function of DIODE 4007 in detail.

      harshad patel

    135. Sir….

      I am on my project to make solar powered bicycle.
      I am using 12v dc 200rpm motor to drive the cycle. Is 12v dc lead acid battery is enough to run this motor? If so which solar panel is required to charge this battery.
      Please help me, i am mechanical student and weak in electronics. This is urgent. Please. My email address is ngnaneswar@gmail.Com

    136. Dear Sir,

      Please I have a 2KVA inverter that is using 24VDC, please i need your advise on how to make this circuit charge the batteries, below is my proposal;

      1. change the solar panels to 24v
      2. change the zener diode to at least 9V
      Best regard,

    137. Sir, i need a solar charger solution with hi low voltage cut off for 6v 4.5 ah battery, which charges the battery speedly.

    138. Hi!
      I want to charge a 26 volt battery with solar panels, but I have more than one solar panel.

      I have seen that you replied to a another person that he can change the Zener to adapt the circuit to a battery o 12 volt.

      Can I do the same? I mean, change the zener of the circuit to a 26 volt Zener in orden to charge a 26 volt battery

    139. Honestly, i must commend u for ur good compositions and constructions,especially for this one. I want to ask if u can sustitute the solar for AC?. Which of course u know would need u to rectify.

    140. Mr.D.Mohankumar I’m gonna do a mini project on solar bt charger for mob phone.can you precisely give me the requirements?

    141. sir
      can i make portable solar charger by this circuit.plz help me about portable solar mobile charger.

    142. Sir

      I am planning to do a mini project on mobile phone chargers using solar cells
      Sir would you please help me out with circuits.
      And sir wat will be the efficiency of such chargers

    143. sir , will you post me a circuit having ability to convert the 0.7v (output from solar cell) to 3.0v
      please send me a circuit regarding.
      thank you…

    144. Please, you can use 3 lithium battery in series in this circuit? Thank you.

    145. sir,

      does this circuit really works? hope it will and thanks by the way.


    146. Dear Mr. D

      I am a final year student and i would like to do a solar project which its concept is rooted from the problems rural hospitals are facing. I am new in the solay systems and i thereby seek your help in transforming my concept into reality. My email is; mayizab@yahoo.com.

      My regards.

    147. Sir can u help me to make a solar mobile phone charger! is it possible by modifying this ckt or by other ckt plaese help me if any one else can help contact me on e mail id erjaswantsingh165@gmail.com

    148. can we use 12 volts 1 ampare transformer in place of solar cell to charger the sla battery of 6 volts 4.5 ampares

    149. vijay kumar sharma says: on January 21, 2012 at 8:22 am

      Where I can get 12 volt solar penal

    150. You can get Solar panels from http://www.espareonline.com
      it is very economical & high Quality


    151. Hello, I’m needing a PWM controller that can handle a 24volt array of up to 5000 watts. Do you have any schematics for that?

    152. HELLO SIR,

    153. sir,when there is prob. of sunlight then to store previous energy of light for continous charging purpose what we have to add?????

    154. Please….send to me a solar charger…output 12V/4Ah
      secuit schematic

    155. Sir,
      Can you please email me 6V solar charge controller circuit diagram. I have a 3 Watt panel that gives 8 volt . I need to charge 6V , 5 Ah battery .

      Thank you,

    156. I have 10w module. Want 12 v /1amp current ckt please sire mail me

    157. Hello D.Mohankumar ,
      regarding the above circuit , will it give a constant output if we consider that solar input is variable 0-12v. plz feed me back i need to make sure that the solar charging circuit gives a constant output that can charge a 6v rechargeable battery .Thanks

    158. How would I change it to charge a 3.7V mobile battery??

    159. Hi, i am wondering to how many batteries we can charge through this project, is it that only one battery can be charged at a time, i wish to charge around 4 batteries, Is it possible

    160. hi friends,any one complete solar project
      give your ph no

    161. I believe this circuit is a constant voltage output… not constant current. R1 and VR1 setup a voltage diver circuit to set the output.
      the circuit will not output more than 1 Amp. the Series Resister(R3) will also limit the current.
      Set VR to voltage 2 volts higher then what you need… then make sure the Zener diode is the voltage you actually want.
      You are setting VR (Regulator output) voltage to be 2 volts higher then Zener Diode Rating. Depending on Zener Diode Tolerance, it can be as low as .7 volt above the regulator output before the Zener Diode starts to conduct.

    162. http://www.cirkits.com/ has a solar controller that is a kit..


      has on that is 6 – 12 and 24 volt kit.
      Kit is discontinued but you can still build if you have the proper skills and understanding.

    163. sir,i want to know that,can we utilise the wind get when train running,as the power for train?plz reply to the mail ID sir

      I’m WAITING FOR U.

    165. Sir,
      I have 75w x 3 solar pannel and 150ah 12v battery.what can change in this circuit to charge the same battery.
      please suggest me…..

    166. dear sir
      can i use the same circuit for charging a Li-ion battery 3.7v,900mAh with the use of a solar panel

    167. As a complete newbie, find the diode direction on this circuit to be a bit confusing. With the diode between the power and the IN pin of the ICI how does the power get through t if placed i the orientation it is?…or have I got something wrong in my head regarding shematics?


    168. As a complete newbie, find the diode direction on this circuit to be a bit confusing. With the diode between the power and the IN pin of the ICI how does the power get through t if placed i the orientation it is?…or have I got something wrong in my head regarding shematics?


    169. how can i increase the current level
      “I have 12v solar panel and a charger which charges the nokia phone batery but of battery 1800mAh cant chared by it ” so what to do “

    170. Hello and good afternoon. I’m making a solar powered automatic water pump.
      The motor of my water pump could deliver 6 to 12V and i am wondering how do i connect the solar power to the water pump? and do i need a battery charger too.

    171. Dear Sir,
      I am interested to make electronic useful mini projects (Circuits), but i dont know where from i get the required components (spare parts)like Different IC’s, LDR, Relay etc. Can u help me, how to get electronic basic spare parts. ie(Supplier Address & Telephone no.)
      Pl mail me on arunakulkarni_2006@rediffmail.com

      Thanks in Advance
      Arun Kulkarni

    172. sir, i want to charge 220 volt battery, then how much capacity solar panel should i use, for home requirement..
      i wnat to connect 2batteries in series and invert it to homely use sir, please guide…

    173. Dear Mr.D.Mohankumar,

      I’m make 6V Battery Circuit, can you send me any small size PCB design Circuit.


    174. Dear sir .Can you help me in designing a solar charger for mobile cellphones with a lamp and a torch using a 12v solar panel as our supply

    175. hiii hari i am satish from karnataka city bellary i want to make some electronics experments i need ur help please help me…… contact me 9611678969

    176. Please….send to me a solar charger…output 12V/4Ah and 12V/7Ah
      secuit schematic

    177. Hi,

      Can you help me with IC for a charger for a 12V battery which will charge from solar panel ( 12V or appropriate voltage ) which will drive 2 fans working with 12 V DC, 0.5 Amp for 8 hours.




    179. Hello everybody,

      I want to use thic circuit for charging 12v/1.3 Ah battery. Therefore i have some questions:
      1-Can i set(adjust) the charging current?
      for example:130 mA because 1.3 x %10=130 mA

      2-I want to interrupt the charge process when the battery voltage reaches 14.4 volt. So Which value has to be the zener diode? is 14 volt suitable?

    180. Sir, how can i modify the circuit to be able to charge 2 laptops and 3 phones. Please help me

    181. Sir,How to make a auto cutoff charges for 4v battery? Pls help me…

    182. sir,can u pls mail a circuit diagram, which shows the charging of battery as well as direct connection of motor from solar panel.also when battery will full charge it will automatically cut the connection & motor directly run by solar panel..pls help..

    183. sir, i want 60 watt solar pannel to 12v inverter battery charger controller circuits, please send me

    184. Sir,

      I have a solar power module 12v 130watts, it is ok im using solar battery 12v 100ah?

    185. I need to design a portable weigh device with digital output, bluetooth and usb interface. Weighing as low as 10g and as high as 20kg. Help me with a circuit Sir.

    186. Mr. Kumar,

      I have 48VDC input inverter (220VAC output)
      can you provide me how many solar panel required and its wiring diagram.

      • johnjogs says: on June 20, 2012 at 9:35 am

        Hi Jr,

        you need 100pcs of solar cell with 0.5V output and connect in series. For wiring search on google engine, there’s a lot of schematic you can use.


    187. hi, pls include the solar charger circuit

    188. Dear sir,
      I was made that solar charger circuit, i want ask some question sir, where the right place to put LED for a sign when battery is charge or not.

      Hope you can help me sir.

    189. sir i need solar pannel.where it available.pls mail to me.arrond pondyor chaennai

    190. what is the voltage of the capacitor and recistors

    191. pls send me …..battery ckt diagram for connect 12v battery from 18v solar pannel

    192. Sir,
      how to connect variable resistor in circuit. it has three terminals. i have connected one to adj pin, middle pin to collector of transistor, another pin to negative. is it correct Sir?, my circuit gives maximum 8.2 v sir. i am beginner of electronics. help me sir

    193. i wanna charge super capacitor along with the battery by the solar panel can anyone help me to this…

    194. garima agarwal says: on July 6, 2012 at 4:50 pm

      hello , mr. d. mohan.i had made a auto battery chargaer and i want to joint solar panel with it,so can u tell me the circuit requirement for that task.

    195. How about the output battery 12v 7Ah? just change zener diode to 12 ?

    196. what the price for a 12volts solar panel

    197. why this LM317 do not need any capacitor on it?

    198. This is totally bullshit. You burn the charge in LM317. A peak power tracker is needed and a LTM series regulator would be nice in between the output of the peak power tracker and the battery.

    199. Thanks for sharing your knoweldge, sir, changing the value of zener from 6.8 to 20v, could this work to charg 12v 85A battery or if there is any adjustment in this circuitt that would charge

    200. I used to use my solar charger which I connected with LM7805 and USB. Now when I connected it with my both mobiles. It is not working. But when I charge it by USB from my Laptop it does work. Can someone tell me what the problem is ? Is something can destroy in my mobiles ?

      Many thanks in advance


    201. dear sir, i want a charger circuit of solar panel for home lighting. Actually my charger has been burn which is used at home and i am doing B.TECH so i want to do a project on solar panel.sir please mail me a circuit of charger with some important details.

      so please sir help me.

    202. kindly post one to caharge a 12V 70A battery

    203. the circuit gave only 1v output. i used bc 547 instead of bc 548. is it wrong

    204. we are now planning for multipurpose charger ckt, but we haw 3w 12v panel. will it work here. if yes charging current will be less is it?



    207. engineering_student says: on August 28, 2012 at 8:06 am

      With all do respect, this circuit is bad and it does not work with the components provided. To obtain the claimed output voltage. It is impossible to obtain even 6V using a 1K variable resistor on the adjust pin. It must be a much higher resistance. Also, the circuit shown above will never obtain a 9V output before diode D2, because of the zener diode. The voltage prior to D2 will only be about 0.7V above the zener breakdown voltage (due to the voltage loss through diode D2). Furthermore, diode D1 is not needed unless you are concearned about accidental reverse polarity of the solar cell. There should be capacitors on the input and output to stabilize the voltage (reduce low and high frequency oscillations in the circuit-i.e. noise). I did substitute the transistor with a 2N3904, but it is a general small signal BJT transistor, and should function the same way, since the topology being used is a switch, not an amplifier.

    208. Thank you very much for your hardwork. I have a questions. How about i connect a load to the battery, will it be remain in charging or it will divide the output current? And is this diagram also designed for overdischarging the battery?

      • Jim Keith says: on August 30, 2012 at 1:46 pm

        It depends upon the load current. If the load current exceeds the current generated by the solar panel, the battery will discharge. Conversely, if the solar panel current exceeds the load current, the battery will charge, but at a lower rate.

        No, this circuit does not prevent over-discharge of the battery. That would be an interesting circuit to present on this forum.

      • ermsk8er says: on August 31, 2012 at 6:38 am

        The load rated 12v @ 0.30A. Can i use this circuit? My panel is 12v @ 200ma and my battery is 6v @ 4.5AH. I will use a 5v regulator connected to the batt and 5v booster connected to the 5v regulator so that i can connect the load to the booster while charging.. Any suggestion or help will be appreciated. Thanks!

    209. i like the circuit but the Resistor R3 10R,180R values in ohm or k

    210. can u explain to e briefly
      how this circuit function???
      what components make the battery discharge??
      i not understand
      plzzzz explain???

    211. Dear Sir; I want to know how to chage the 12 watts flurecent lamp using solar panel.Give the idea about circuit chager&
      Circuit diagram. Please help me.

    212. solar consultant says: on October 3, 2012 at 9:01 pm

      Thanks to P. Marian for sharing this information with the larger audience.
      This circuit has worked for me without any issues.
      If any one needs any kind of help or facing any issues drop me a note on mysunnyterrace@gmail.com and I will get back to you.

    213. hi, thanks for the great info regarding solar panel.

      I have one question, does mA is important to charge 6V lead acid batery cos u only mention about volt.

      could u please post your circuit/photo for solar cells. currently i have 9 pieces of 5V 50mA solar cell to do this experiment.


    215. Hello I have built this circuit on a protoboard and have checked everything is right I have used all the correct components as per your ExpressPCB schematic can I ask what voltage am I supposed to be getting from the output to charge a 6v battery my multimeter is saying 6.5v and I have turned the VR right up and measures 1024Ohm I am using a 12v source to mimic the 12v solar panels as I have not bought them yet and a 6.8v Zener, I am getting 7v from the out leg of the LM317 also I was wondering if I could replace the VR with a normal resistor to match the required output to charge a 6v battery Please help!!!

    216. wsnusingsolarcell says: on April 25, 2013 at 10:06 am


    217. hai any one can help me in making a charger which converts 6volts solar power to 3.7 volts cell phone battery…pls pls

    218. can someone please tell how he arrived at the value of 10 ohms for the R3 resistor?

    219. That is very useful to learn new comer student in solar Energy.

    220. iam making 6v led lamps ,iwant led pcb total detalus pls send me my email id

    221. T Quadir Choudhury says: on October 31, 2013 at 5:59 am

      I have a 25W panel, The Imax (at Pmax) it says is 1.37A
      The max I could extract is 05-0.6A for 12V battery with the charger above. I also removed the current limiting resistor

      If I connect the panel directly to the battery , I get a larger current.
      Is this a proper way to charge , if not can you please tell me why

    222. Can this circuit charge a mobile phone with voltage 5v ?

    223. sir, if we are giving variable input or by using buck boost converters what changes should do in this circuit??

    224. thank u sir for the circuit ,
      i just have 2 questions …

      1st .. what should i change to charge a 12v , 2.3 ah battery ??
      and how much time will it take??

      2nd .. what does the R3 , 10 ohm / 1w represent ??? is it a normal 10 ohm resistor ??

    225. haloo sir. i need ur help plz told me how can i charge a mobile phone battery by solar charger 6 volts battery what should i have to connect at the output terminal of battery so that battery does not burnt plz sir told me

      thanks to u

    226. can this circuit charge the battery 12v.. i already used 12v solar panel.. but this VR still valid to using?

    227. hello;

      i have sun tracking system,so i want to charge 20 volt and 4 amp from the solar panel, should i replace bc548 transistor with mosfet transistor and replace the variable resistor with power resistor, please any help.


    228. Dear sir,
      I have 24 watt dc fan with lead acid battery 6V,4.5Ah,I want to change this design to solar based design and how much watt panel suitable for this design please kindly help me for the circuit design.

    229. sir,
      i found the circuit very usefull…what else should i do…for i want to stop load when charging..

    230. dear sir,
      how does the VR provide 9V to the battery?
      If i need connect a arduino to the circuit where can i put at??


    231. Saqlain Farooq says: on July 3, 2014 at 1:22 pm

      I want to know the function of diode(1) in the above given circuit.

    232. Hi, nice circuit, where can I put a LED so I know when it cuts off?? thank you.

    233. if this charger is also applicable to ni-mh battery??

    234. What if i use this circuit , in order to charge a mobile phone? by putting the proper telephone cord from the battery to device?
      As far as i know all mobiles charge to 5V.

    235. Sir,how i can charge my mobile from 6volt solar.

    236. can i replaced LM317 by lm7805

    237. Dears,
      I bought a 6 volt 5 watt solar panel and gave direct connection to my cell phone by cell phone in put pin.Phone displays not charging . Where is mistake? How can I rectify it

    238. Hello,

      I am very interested by this topic and by your device.

      I want to do the same device but with a solar panel, and 4xAA batteries or 9V battery.

      The goal is during solar day recharge the batteries and cut off when there are loaded.

      During night, use the batteries to power a standalone xbee device (need 3,3v).

      On the output of the power device i will put a power regulator to deliver stable 3,3v needed by xbee.

      Is it possible to adapt your device to do mine ?


    239. hi Mr D.MOHAN KUMAR
      i want to use it to charge cell phone. i have this solar panel. which circuit i must use?
      thank you..

    240. I have 4 solar cells 5.5v and 450mA each in parallel. My circuit needs 5v and 1A output . How should I proceed? Will there be a current produced higher than 1A?

    241. Hi,

      My output voltage is 7.01 is that correct.

      Setup as follows : x2 6v 3w panels in series.
      Input voltage to circuit 13.6v 3w
      Charging a 6v 4ah lead battery

      Isnt my outout voltage to low, my 1k VR is set fully clockwise.

    242. Does anyone still use this post.

      Also i want to charge a 12v 7ah pb battery. Can i remove the 6v zenor diode and regulate my voltage to 13.8v. What else do i have to remove. Just a basic regulated circuit without compromising the oringinal to much.

      Hope to get a respons.

    243. My brother suggested I might like this web site.
      He was once totally right. This submit truly made my
      day. You can not believe just how much time I had spent forr this info!


    244. hi
      is it possible to use this circuit to charge lipo battery ?

      • Charging a lead acid battery and a lipo battery is totally different. Lipo battery chargers have separate charging mechanism.

    245. Yes it is tru e…..

    246. Good day Mr. D.MOHAN KUMAR, is it ok if I put a led in series on the emitter of BC548 to indicate that the battery is full? Also putting an LED before or after D1 to indicate that their is a PV source input voltage? thanks for you circuit.

    247. Hi
      Is it possible to use this to charge 4 cells of 1.4v?
      Please tell me about thé components zener résister?
      Is a solar panel provided 6v good?

    248. I blog quite often and I genuinely appreciate your
      information. Your article has truly peaked my interest.
      I am going to book mark your site and keep checking for new
      information about once per week. I subscribed
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    249. solar charger for 6volts battery was good but if the battery over charge what should be done can you please explain sir what should be done

      • sleniofernandesyahoo-in says: on May 14, 2016 at 12:21 am

        Hello Mr. Vinay, I had a similar question like yours. I wanted to know how to upgrade this circuit bye adding LEDs to show the charging process and charged process.

    250. I’ve done this circuit for 6 volts 4.5aH battery, LM317 gives max 7 volts with 12 volts 10W solar panel or 12 volts 1A transformer.

      So thinking some thing wrong I have done another circuit which is also giving same 7 volts output even after adjusting VR.

      Please let me know the issue.

    251. Afsorul Haque Barbhuiya says: on August 12, 2015 at 7:20 pm

      Hi sir,
      I want to use a solar panels having capacity of 12 volt that can provide sufficient energy to charge a battery of 8.4 volt. Also I want to charge my smartphone by using solar power because my mobiles charger connector has been corrupted , so please sir help me to initialize the system that can provide sufficient energy to charge my smartphone with out connector .Please sir……..

    252. i have toshiba c-640 laptop and 10w solar panel .on the charger of laptop marked output is 19v 3.42A .
      can i use this circuit diagram to charge a laptop? and can i add a voltage divider in this circuit a 5, 16,19 and 21 volts output? can you help me.

    253. Sir ,
      I have a 5.8 v solar panel and I want to charge li-ion battery (2010 Mah) what should be the circuitry and equipments I will require for the same..

      Thanx in advance…

    254. Sir I want to make a solar lamp and my solar panel configuration is 7V 0.1mA and we want to charge NI MH thee cell battery total is of 4.5V. So please tell what are the changes requied in this circuit.

    255. Josephs Christian says: on December 17, 2015 at 8:20 am

      Please Sir, how do you calculate the base resistance used alongside the Zener diode to switch on the cutoff transistor? Thanks.

    256. Plz tell me sir erickshaw roof panel price and bulk panel send rate list only panels and all it am price

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