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2 Simple Battery Desulfator Circuits Explored

2 Simple Battery Desulfator Circuits Explored

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In this article we investigate 2 simple yet powerful battery desulfator circuits, which can be used to effectively to remove and prevent desulfation in lead acid batteries. The first method uses PWM pulses, while the second method implements a ordinary bridge rectifier for the same.

Sulphation in lead acid batteries is quite common and a big problem because the process completely hampers the efficiency of the battery. Charging a lead acid battery through PWM method is said to initiate desulfation, helping recover battery efficiency to some levels.

What is Sulphation in Lead Acid Batteries

Sulphation is a process where the sulfuric acid present inside lead acid batteries react with the plates overtime to form layers of white powder like substance over the plates.

This layer deposit seriously deteriorates the chemical actions inside the battery while charging or discharging making the battery inefficient with its power delivering capabilities.

Normally this happens when the battery is not being used for long periods and the charging, discharging processes are not done very frequently.

Unfortunately there's no effective way of tackling this problem, however it has been researched that the jammed sulphur deposits over an effected battery may be broken down to some extent by subjecting the battery to high current bursts while charging it.

These high current charging pulses should be well optimized through some control circuit and should be diagnosed carefully while implementing the process.

1) Using PWM

Implementing the method through PWM controlled circuit is probably the best way of doing it.

Here's an excerpt from wikipedia, which says,



" Desulfation is achieved by high current pulses produced between the terminals of the battery. This technique, also called pulse conditioning, breaks down the sulfate crystals that are formed on the battery plates. Short high current pulses tend to work best. Electronic circuits are used to regulate the pulses of different widths and frequency of high current pulses. These can also be used to automate the process since it takes a long period of time to desulfate a battery fully."

https://en.wikipedia.org/wiki/Talk%3ABattery_regenerator

The circuit of a PWM battery charger discussed here can be considered as the best design for carrying out the above desulfation process.

How the Circuit Functions

The IC 555 is configured and used in its standard PWM control mode.

The output from the IC is appropriately amplified through a couple transistors so that it is able to deliver the said high current pulses to the battery which needs to be desulfated.

The PWM control may be set at low "mark" ratio for implementing a desulfation process.

Conversely if the circuit is intended to be used for charging normal batteries, the PWM control may be adjusted for generating pulses with equal mark/space ratios or as per the desired specs.

The controlling of the PWM will solely depend on an individuals personal preference, so should be done correctly as per the battery manufacturers instructions.

Failing to follow the correct procedures may lead to fatal accidents with the battery, due to a possible explosion of the battery.

An input current level equal to the battery AH level may be chosen initially, and reduced gradually if a positive response is detected from the battery.

2) Desulfating with a Transformer and Bridge Rectifier Circuit

To make this simplest yet effective battery desulfator with charger circuit you would just require a suitably rated transformer, and a bridge rectifier. The design not only desulfates a battery, it keeps the new batteries from developing this issue and simultaneously charges them to the desired levels.

At the beginning of this post we learned how to desulfate using PWM concept, however a deeper research shows that the process of desulfating a battery may not necessarily require a precision PWM circuit, the supply just needs to be oscillating at some given rate, and that's enough to initiate the desulfating process (in most cases)... provided the battery is still within the curing range and is not beyond the reviving state.

So what would you need to make this super simple battery desulfator circuit which will also charge the given battery, and additionally possess the ability to keep the new batteries from developing the sulfation issue?

A suitably rated transformer, a bridge rectifier and an ammeter are all that's needed for the purpose.

The transformer voltage must be rated approximately 25% more than the battery voltage rating, that is for a 12V battery a 15 to 16V supply may be used across the battery terminals.

The current can be approximately equal to the Ah rating of the battery for those which need to be revived and are badly sulfated, for the good batteries the charging current could be around 1/10th or 2/10th of  their Ah rating. The bridge rectifier must be rated according to the specified or calculated charging levels.

Desulfator Schematic using Bridge Rectifier

How Bridge Rectifier Operates as a Desulfator

The diagram above shows the bare minimum requirement for the proposed battery desulfator with charger circuit.

We can see the most standard or rather crude AC to DC power supply set up, where the transformer steps down the mains voltage to 15V AC for the specified 12V battery.

Before it can reach the battery terminals, the 15V AC goes through the rectification process through the attached bridge rectifier module and gets converted into a full-wave 15V DC.

With a 220V mains input, the frequency before the bridge would be 50Hz (standard grid spec), and after rectification this is supposed to become double that is at 100Hz. For a 110V AC input this would be around 120Hz.

This happens because the bridge network inverts the lower half cycles of the stepped down AC and combines it with the upper half cycles, to finally produce a 100Hz or 120 Hz pulsating DC.

It is this pulsating DC which becomes responsible for shaking-up or knocking down the sulfate deposits on the internal plates of the particular battery.

For a good battery this 100 Hz pulsed charging supply ensures that the sulfation ceases to occur on the first place and thus helps to keep the plates relatively free from this issue.

You can also see an ammeter connected in series with the supply input, it provides a direct indication of he current consumption by the battery and provides a "LIVE update" of the charging procedure, and whether or not anything positive might be happening.

For good batteries this will provide the start to finish info regarding the charging process, that is initially the needle of the meter will indicate the specified charging rate by the battery and may be gradually expected to drop down to the zero mark, and that's when the charging supply needs to be disconnected.

A more sophisticated approach can be employed for enabling an automatic cut-off once the battery is fully charge by employing an opamp based automatic battery full charge cut off circuit (the second diagram)

SHARING IS CARING!

About the Author

I am an electronic engineer (dipIETE ), hobbyist, inventor, schematic/PCB designer, manufacturer. I am also the founder of the website: https://www.homemade-circuits.com/, where I love sharing my innovative circuit ideas and tutorials. If you have any circuit related query, you may interact through comments, I'll be most happy to help!






147 thoughts on “2 Simple Battery Desulfator Circuits Explored”

  1. Many thanks for this selfless service.
    I will go through the circuitry and do the needful, while hoping that I will not come across any difficulty as I set off to prepare it.
    Thanks.

  2. Thanks a million times for finding time, out of your obviously tight schedule, to go through my mail and respond so urgently.

    I wouldn’t mind a charging current that could be varied between the neighborhood of 0 to 20A .

  3. FRANKLY SPEAKING, YOU’RE REALLY DOING A GREAT JOB!!! SOMETIMES I WONDER HOW YOU GET REMUNERATED DOING ALL THESE…… MY WORRIES IS HOW TO GET A CHARGING CIRCUIT WITH ADJUSTABLE CHARGING CURRENT. PLS e-mail me.

  4. hello sir Swag .. is the circuit above whether it can be connected with car alternator with 60 Ah battery and if required fuse. thanks (sorry I use google translation ?)

  5. Hi Mr. Swag,
    Thanks for the reply. I used the 1n5408 diodes in series. Would I measure the current at the output of the Mosfet or the output from the diodes?

    • Hi Peter, you can connect the meter in series with the positive supply line …anywhere…. the current must pass through the meter, that’s the requirement.

  6. Hi Mr Swag,
    I have now built the circuit with the diodes in series, but find that the diodes get very hot after about 10 minutes. The Ic and mosfet however do not. Is this normal?
    I have checked for solder bridges and found none. Input to the diodes is 20vdc and to battery pos 15.2 VDC. Output from the mosfet drain is 12.4VDC. Any help will be appreciated.

    • Hi Peter, which diodes did you use? check the current consumption during the charging with a series ammeter and make sure to use diodes that is rated 2 times more than this measured current consumption

  7. Hi Mr. Swag,
    Hopefully the last question. Can I use a 7815 voltage regulator instead of the diodes? What would be advantages /disadvantages.

    Many thanks

  8. Hi Mr. Swagatam, thanks for the very good information all over the site. I have an AC to 24v DC transformer and would like to know how to get the voltage down to 15v and can I then use that? Your help is much appreciated.

  10. Faith,

    I think you are not able see my replies because you are not pressing the "load more" button….unless you do this you won't be able to see the hidden replies.

    your second question is very strange, and It can be difficult for me to figure out the solution until I check the circuit practically…

  12. Sir this what i observe i noticed that even when there is no gate voltage to the mosfet the battery is still charging i went as far removing the 555timer to confirm this and notice the battery was charging please what could be the cause and how to correct it thanks

    • Faith, I think your mosfet is already burnt, or was originally faulty….instead you can try a TIP35 BJT, because BJTs are normally more rugged than mosfets and do not get burnt mysteriously…

  13. Hi you are the best
    I made this charger and its really working thank you very much please how do i include cutoff to this circuit

    • thanks Faith, you can use the following circuit for the cut off

      ttp://www.homemade-circuits.com/2011/12/self-regulating-lead-acid-battery.html

  15. Thank u for the reply

    Ok can connect mosfet in parallel so that the current can be shared among them.

    secondly the circuit seem not to have charge control which means one needs to monitor the battery so that it dont get over charge if that be the case how can i add a cut of can i use this circuit

    https://homemade-circuits.com/2013/03/automatic-lead-acid-battery-charger.html?m=1 from this your post

    Again is the mosfet N-channel or p-channel

    If N-channel is it the drain that gose to the negative of the battery? While source to ground

  16. Sir I'm really proud of you for ur good works and quik response you are one in a million. Sir about the above circuit can it be use to charge a 12v@600AH and if yes what modifications should i do. secondly the circuit seem not to have charge control which means one needs to monitor the so that it dont get over charge if that be the case how can i add a cut of can i use this circuit https://homemade-circuits.com/2013/03/automatic-lead-acid-battery-charger.html?m=1 from this your post if yes how i attached ithttps://homemade-circuits.com/2013/03/automatic-lead-acid-battery-charger.html?m=1

    • Thank you Faith,

      you can use the above circuit for charging any desired battery, through appropriate modifications in the mosfet value.

      for your application you will need to replace the existing mosfet with a 100amp rated moefet…

  17. it means your 555 is not working or a is faulty, replace the 5K pot with 100K and replace the pin6/2 capacitor with a 100uF, and check the output if it generates the pulses or not…if still not, then you may think about changing the IC

  18. I just build it, but not work and then checked using an oscilloscope nothing pulse or voltage spike Yo the battery.
    Adivice me, give solving about this problem.

    • connect it from pin#3 to ground through a 1K resistor, but the LED will appear continuously lit with any frequency higher than 4Hz

  20. Hi swagatam please i need your help i have a 12v battery@200A and they are 4 in number connected in parallel and i want to make a charger for it, a charger that provide at least 80A for the battery connected in parallel please can you give me pulse width charger circuit with cut off that can handle such high current thanks

  21. can i use irf640 instead of irf540…..or is it work without toroid coils which are arranged in order to make hi pluses.. that is 1000uH and 200uH

    • torroid coil is not necessary….i am not sure about IRF640, if its current/voltage specs are compatible then it can be used

    • IC 555 will produce a voltage that's exactly equal to the supply voltage, so in the above case the output will be 15V at pin3…not an issue for the mosfet.

  24. hi mr swagatam,i hope you are good
    i suggest to add a simple mosfet driver using a transistor cause 555 output voltage is weak and thus will overheat the mosfet,i tried before to connect 555 output to mosfet gate with a resistor and mosfet gets hot.

    • Hi Hisham, I am good thanks,

      555 IC has an output that's more powerful than most ICs, however mosfets never require a powerful signal to operate, they just need a voltage above 9V for operating optimally.

      You can try reducing the gate resistor to 10 ohms and check the response….or may be the load you have connected could be above the mosfet range

  25. Interesting circuit. I had a thought, perhaps this could be combined with adding a very small (<3ml) of acid to each cell technique for unmucking dead SLAs typically run to death in UPSs.
    If they are at 0.0V I doubt any technique will work but its the ones which have good voltage but next to no capacity that could be salvageable.

  28. which simulator i can use to make this circuit and can have a dead battery in it for charging?
    if you plz don't mind…can you plz send me the whole process from the begining till the battery desulphation.. what all the pins are doing … plz .. i will be gratefull to you.

    • simulation is not required, just procure the parts and the build the circuit, the circuit is explained in the articles itself…

  29. Good day to you sir.
    Thank you for sharing all the great work.
    A few questions about this circuit :
    1. What is the 5k POT for ? & how to adjust it ?
    2. Does the IRF 540 need a heat sink ?
    3. The negative of charger is directly connected to IC Pin #1 ?
    4. How to connect a LED to this circuit, that illuminate when connect to battery ?
    5. Any harm if connect to the battery permanently ?
    Thanks a lot in advance .

    • Good day Alaa,

      1) 5K is for playing with the output pulse width, which might in turn help to implement a optimal desulfating effect….it could be a matter of some trial and error and dependant on the connected battery condition. however it's not so crucial, you can keep it at the center to begin with

      2) Normally it shouldn't require a heatsink, however you can test it practically by touching it, to be on a safer side..

      3) yes the negative of the charger needs toeb connected to the pin#1 line of the IC

      4) charging indication might not be possible, however an ammeter may be connected in series with the battery positive to get a direct reading regarding the batt response to the charging procedure.

      5) yes if the battery begins responding and desulfating…an ammeter can be used for monitoring the same as explained in the above point

  30. Thanks Sachin,

    shorting would be advisable only if the battery has sufficient charge on it, unless it's charged fully, shorting won't induce any effect on the plates.

    The pulse charger explained in the above article is the ultimate way of dealing with this mess, if the battery responds and wakes up to the pulsed charging only then the shorting of the terminals can be tried, however as shown in the video a high amp resistive load would be more appropriate than shorting since here we don't have to worry about the delay period in ms

  31. Sir, I'm planning to add this circuit on my existing 72v ebike charger. It has 6 pcs.12v 20ah battery connected in series. Would it be possible? What ic regulator should I use for LM555's supply voltage? And what mosfet would you recommend?

    • Hi Jusi, yes you can try it, just make sure to disconnect the battery positive from the shown point and connect it with the +72V supply……..and connect the positive of the circuit with the positive of last 12V battery in the series which has its negative connected with the bike's ground or the bike's negative….

      the negative of the circuit can be joined with this ground that is the common ground line.

  32. Thanks Mikel,

    changing 1nF to 1uF will reduce the frequency or the pulse rate, but that will not affect the results, so it's OK.

    the mosfet and the supply voltage are also OK, but the current input must be well over 20 amps for desulfating a 100AH battery, so make sure the supply current is at this level.

  33. Hi Mikel,

    you can connect an LED across pin3 and ground with a series 1K resistor but it will appear continuously glowing due to high frequency pulses from the IC

  38. Hi,

    I started building your old circuit and only realized you have changed them ,but I have bought parts for the old diagram,so can I build the circuit without the inductor with the TIP122 ,or should I Change it IRF540.

    • Hi, I changed the circuit a long time ago may be a half year ago, it's strange you are building it now.

      I would recommend you to make the above shown design instead of the earlier one since adding a coil will not make much of a difference.

  39. Hi Mr. Swagatam, newbee here.
    So I've finished assembling the circuit, how to tell that it's working before I start attaching it to the battery? I mean is there some type of indication there or do i've to measure anything first?
    thank you.

    • Hi Imanul,

      There's no circuit which can guarantee a perfect desulfation in dead batteries, so you can only hope that this circuit produces the intended results as it's designed as per the standard recommended specifications.

      Use the circuit for about 4 hours and then check the battery with an appropriate load, if the charge sustains for an appreciable amount of time you can assume it to be revived, otherwise you may repeat the procedure with some change in the PWM frequency and/or the input current to the circuit and check the response in a similar manner.

    • …please change the 1n caapcitor with a 10uF capacitor.

      connect an LEd across pin3 and ground via a 1K resistor.

      When switched ON this LED must flash rapidly indicating a proper functioning of the circuit, changing the pot would change the flash rate on this LEd

      you can keep the new capacitor connected and use the circuit for the required purpose, it won't make any difference in the performance.

  41. thank you I already done it just downloaded the ic pin out then I know the number 1 leg is the ground.
    thank you again for your fast response and attention.

  42. hi
    I just realise in the circuit there is no ground to the circuit?
    if we use power supply to connect to this circuit the plus 15V pole goes to the battery and the circuit where then the negative pole goes?
    I know if I use coil and transistor I have to connect the negative pole to emitter but on mos fet not sure looks like this one joint missing from the circuit
    could you please correct me if I am wrong?

    • So Avenger is saying that there is no coming back from hard crystalline PbSO4 .
      OUCH!
      One should have all batteries under full time trickle charge.

      Avenger ,…. which one of Swagatam's designs did you use for your charger?

      Carl

  43. Lead Lead Sulfate PbSO4 is part of battery charge discharge cycle. The structural form of PbSo4 makes the difference. While amorphous PbSo4 is reversible while hard crystalline PbSO4 is irreversible and inactive. Shallow cycle batteries never have to be discharged under 12.5 volts. If this happens an immediate charge will consume and transform PbSO4 in to Pb, H2O, PbO2 and H2So4. If let staying there for sometime the PbSO4 crystallize and turns inactive. To make a long story short if battery isn’t in use immediately use Float charging with a battery trickle. Harbor freight tools sell a battery trickle (Floater) for $9.99, which I bought on sale for $6.0. The manufacturer 13.2Volts was only a promise, but replacing VR1 with a 100-Ohm trim pot, I can adjust the voltage from 12.6V to 14.25V. I set it at 13.25V but this is only the first aid. What you need is EQUALIZE the BATTERY; this can be done at 14.5V for some hours. During this process the strong cells start boiling but the weakest cells continue charging. This can be done with a battery tender. I bought one from Wal-Mart connected to my VW Touareg and the next day the relay was chattering ON / OF non-stop. Measured Voltage a found 14.85 Volts. The electronic system of the car was fighting hard against this stupid tender. I solved the problem building up my Battery Tender with precision voltage Window 14.5V stop charging and 12.6V restart charging giving the battery a chance to rest, RELAX. Charging a discharged battery you have to deal with Bulk Charge Current Density that depends from electrode surface and is expressed on mA / Cm2. If a have to deal with an accidentally fully discharged battery I use my Automatic Smart Battery Charger, with Equalizing and reconditioning features.

  45. Hello Swagatam,

    I would like to build a hi/lo adjustable relay/contactor.
    Say ….12v on 13.5 off
    I could then put it in series with any charger.
    It would be great for maintenance and prevent over charging.

    A variant of this could also kick in a discharge cycle.
    This would be good for desulfating.

    Do you have a design lik this?

    Yours
    Carl

  46. Hi Swagatam

    Since I was focusing only on the mosfet so I didn't gave you the details of the other sections.

    As mentioned earlier, one cycle consists of mainly 3 steps + 1 step to monitor battery voltage. Each step is controlled by a 555 and another 555 is controlling all these 4 ICs (the entire cycle). If you want to have a look at the circuit, here it is.

    https://dl.dropboxusercontent.com/u/20969135/Desulfator%204-stage.gif

    I am sorry, that is maximum available resolution of the picture.

    Now, I repeat my question in other way. If the mosfet can be driven directly by the 555, why the author deployed 0.8A transistors to drive the mosfet. You can find them at the top-right corner. I haven't linked the website as per your general instruction however, if you want to see the circuit description I can send you the link.

    • Hi Abu-afss,

      It could be for allowing the mosfet to conduct and restrict correctly, especially the use of the push-pull (PNP/NPN) stage which ensures safe charge/discharge of the internal cap of the mosfet, because as we all know how sensitive these mosfets can be at times.

  47. Hi Swagatam 🙂

    One complete cycle includes 3 steps:

    1) 15 sec pulse charging
    2) 1 sec delay for settling
    3) 100ms shorting battery terminals

    I am just curious about the driving of the mosfet as I asked in my previous post.

    • Hi Abu-Hafss 🙂 how are these three steps implemented because i can see only one active input from the IC 555.

      I wanted to know the relevance of the transistor stages for answering your question correctly.

      Normally we know that a mosfet gate can be integrated with any IC output may it be a 555, a cmos or a opamp, as long as the voltage is below 15V

    • Hi Abu-Hafss,

      How does this circuit desulfate…is it by charging and shorting the battery alternately? I could not understand the concept.

  49. Hi Swagatam

    I have read some of above posts talking about an inductor L1. Where is that inductor, I can't see it in the circuit or any reference in your article?

    By the way, I am working on a trickle charge desulfator. I am considering to integrate a circuit to measure battery's internal resistance (BIR). There are a few BIR measuring circuits on the net but, they need to take occasional measurement manually. Here are two of them:

    https://dl.dropboxusercontent.com/u/20969135/internal-resistance-tester-for-batteries-2.jpg
    https://dl.dropboxusercontent.com/u/20969135/accutest.jpg

    My idea is to have three-LED indication……..the red LED to indicate high resistance, yellow to indicate medium and green for very low resistance. The BIR circuit will operate in parallel with the desulfator circuit. The illumination of the green LED would indicate that the battery has been desulfated, now it is ready to use.

    A relay could be used to connect the BIR circuit to the battery periodically to check the status. A latch can be deployed to keep the indicator LED on but, I just cannot sort out how to get the output on LED as the output is just 5-50mV.

    Can you please help me in this regard? If required, I can send you the links of the sites to have the description of those circuits.

    • Hi Abu-Hafss,

      In the original design I had used an inductor but later found that it could be avoided and came up with the present design , the inductor related comments that you see were posted with reference to the earlier design

      A BIR could be a very useful ad-on.

      50mV can be amplified by using a opamp may be. What do you think?

    • Hi Abu-Hafss,

      I am not able to recollect the previous discussions and the simulation made by me with reference to this diagram, so not able to figure out much about the circuit, if you can point out specific concerns in your diagram then probably I can try suggesting my opinions.

  50. please ignore these initial comments, the diagram has been modified and updated differently, so these comments have no relevance with the present diagram.

  52. Thanks again Swagatam, will update the thread with my results.
    btw, I read somewhere (maybe here..) that the high current pulse may burn out shorted cells restoring even batteries that are considered unrepairable.

  53. Hi Swagatam
    Finally have parts to make the pwm but looking for a hi current supply.
    It occurred to me that lead acid batteries will not sink as much current as it starts to get full. Does the circuit take this into consideration ?
    When the transistor is on, is it essentially grounding the battery ?
    When it is off, is there any ringing without an inductor ?

    Sean

    • Hi Sean,

      If the voltage is set at some higher level then that will force the battery to sink the current which in turn will hopefully initiate the desulfation process.

      Here you can try with a 15V DC, current may be equal to the AH level of the battery and the pot set to provide short pulses.

      When the transistor is ON, it connects the negative of the battery to the negative of the power supply completing the circuit for the battery so that it receives the required charging pulse.

      No, there won't be any ringing effect due to the absence of an inductor.

    • hi Swagatam,
      Thanks again for your reply. How do I limit the current ?
      I planned on using an old server power supply or rewinding the secondary of a microwave transformer. Won't the circuit try to pull all the current it can unless its limited ?
      Sean

    • Hi Sean,

      The circuit will not draw anything above 5mA, as long as the voltage does not exceed 15/16V mark, above this anyway the IC555 would get damaged, so I don't think any current control for the circuit would be required.

    • Hi Swagatam, I think you mis-understood my question.
      With your circuit you recommend limiting the current to the battery initially to 1C. so if I have a 40AH battery, I should limit the pulse current to 40AH. I was asking how I could do this since I don't have a power supply with a current limit. I am thinking of making a power supply by stepping down 240VAC to 15VAC and rectifying it. But this will not be limited. Is there a clever way to control the max current the battery draws ?

    • Hi Sean,

      You can select a transformer rated at around 20 to 30 amps, that will itself take care of the current…actually the current is not a critical value, anything higher than the normal charging method can be employed, and expected to work here.

  54. Thanks for your clarification. I was curious about the use of the inductor (i.e. collapsing magnetic field/pulse, etc).
    Anyhow, I will try this circuit out as its simple enough to make. I would like to try to revive some large capacity (100AH) NiMh batteries I have pulsing with high current. I am hoping the technique will lower the internal resistance of the batteries even though the chemistry is different (i.e. they don't sulphate).

  55. Thank you Sean,

    Actually the circuit has gone through many changes since it was first posted, so please ignore the previous comments as those are with reference to the previous diagram which had quite a few flaws.
    The present design looks to be easier and viable.

  56. Hi Swagatam, your circuits are incredibly practical. Thanks for sharing and explaining.
    I am a bit confused as I read the thread as I saw reference to a 100K pot and L1 inductor but the circuit above for PWM 555 pulser does not show these. What am I missing ?
    2.bp.blogspot.com/-L9UBEjJp8XU/UUQLd8oW6YI/AAAAAAAADkk/FlaSh6PwIos/s1600/battery+desulfator+circuit.png

    Sean

  58. Hi Swagat,
    I need a signal strength meter for direct to home disc alignment at roof.
    Can it be made simply at home with transistor and led.
    Thanks

  60. Thanks Swagat,
    Tryed smthing diffrnt with the stablizer that i must share wid u.
    There are 5 taps in auto transformer, 1st n 3rd tap has been used as input with a relay control and rest for output wid 2 more relays.
    I inspected the 1st relay status at power on, it was making 1st tap as as input for 1 sec then change it to 3rd tap as input, so there was high volt at power on.
    I interchanged 1st and 3rd tap input with relay.
    Now its working good .

  61. Thanks Swagat,
    sorry for one more problem,
    I inspected the stablizer, it has 24 volts relays, so i need to operate the "delay on" circuit on 24 volts instead 12 volts.
    What modification i need?
    Thanks

  63. Hi Swagatam, I have installed automatic voltage stabliser for home supply,
    the only problem is, when it starts, initialy it supply high volts(300 ) for less den 1 sec. den it functions well..
    Pls let me know what is the problem n how can i fix it..

  65. Swagatam:

    Swagatam:

    Thanks for your reply and recommendation. If working at 555 with 5 volts regulated from 7805, the oscillation frequency is not affected?

    Are pleased to greet and congratulate again the excellent circuits published.

  66. Swagatam:
    Excellent circuit, I'm about to try arm. I'd appreciate if you tell me regularly cnveniente a zener and 100 ohm resistor voltage to the 555 and ensure it does not overheat.

    Thank you for your attention

  67. Good day, Swagatam,

    I didn't get nF capacitors (not available at the shop I went to), I bought a 1 microF and a 100 microF. If I substitute these into the circuit, how will it affect the output?

    Thanks,
    Satyam.

    • Good day Satyam,

      The circuit needs to be operated with high frequency so a 1uF or 100uF will not work.

      1nf = 0.1uF, so can try other closer values like 0.22uF etc. or any value between 0.01uF to 0.1uF will also do.

    • Good day,

      Thanks for your quick response. I've built the circuit with the components that I described, however I'll keep looking for the correct capacitors. (I got some surface-mounted caps yesterday, but destroyed them trying to install them.)

      I suspected that my frequency would be affected. Using f= 1/(0.693 x C x (R1 + 2R2)), the frequency of my circuit would be somewhere around 300 Hz, whereas your design is for 300 kHz. Does that sound about right?

      At any rate, I'm using it on a number of car batteries where I suspect sulphation. Will come back & update when I replace the caps, or with results.

      Best regards.

    • Higher frequency would produce better effects according to me, however the pwm pulses would finally decide the optimization rate.

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