Readers are advised to proceed with the construction of the presented circuits only after understanding the concepts from the core. Not adhering to this can lead to failures and frustrations.

Search This Blog

Loading...

Tuesday, May 15, 2012

Battery Desulfator Circuit Explained

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.

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.[16] 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."

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

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.





142 comments:

  1. Great!!!! You are genius

    ReplyDelete
    Replies
    1. how can i indigate this is working correctly irf 540 get heat?

      Delete
  2. Sorry to disturb you again and again,How can I understand that my battery need desulphator,
    and how to adjust the 100k preset

    ReplyDelete
    Replies
    1. If it does not charge within 10 hours or gets flat within minutes of use.

      Delete
    2. Hi, I don't see any 100k trimmer in your circuit? I have a 100Ah battery. Do I have to inject 50 amps to it? Best regards.

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

      Delete
  3. How much amp is required for 7 Ah Battery

    ReplyDelete
  4. I made this circuit but led does not glow and ne 555 get extremely heated ,please guide

    ReplyDelete
    Replies
    1. The IC will get hot only under three conditions:

      If the operating voltage is higher than 16V

      Pin 3 is not connected with a resistor,

      Other pins are connected wrongly.

      Please check the above issues first.

      Delete
  5. Hi swagatam,
    i bought the parts today and will start making this by next holiday. but i don't want to explode my battery. So please explain how much i turn the 100k pot?

    ReplyDelete
    Replies
    1. Hi Savyasachi,

      Before connecting the battery set the output voltage across the battery points of the circuit at 14 volts, by carefully adjusting the pot.

      Delete
  6. in PWM, you need to send High voltage or Current, if we set it to 14 out put will it help in removing the sulfur form the plate. kindly let us know how it works, can we design a better circuit to indicate its working. i also suggest to include a fuse for safety for polarity and other effects

    ReplyDelete
    Replies
    1. A pulsating high current is good for the required actions, just as given in the above article.

      15V @ 1/2 battery AH rate would be better with a mark space ratio of 1:3 high:low pulses.

      Fuse would be good for avoiding short circuit hazards.

      Unfortunately there's no circuit which can directly indicate the proceedings.

      Delete
    2. Thank you very much Sir, can you help in designing one with an indicator and with safety fuse.

      Delete
    3. You are welcome!

      A fuse can be added in series with the battery positive line.

      An ammeter can be used in series with the positive of the battery, in between the fuse and the battery positive.

      A dead battery would indicate no response over the meter. In case the sulfator circuit induces any effect, the meter would start showing the current and the charging rate as a result.

      Delete
    4. Can you help in designing digital amp and volt meter for DC and For AC

      Delete
    5. I'll try to find s suitable circuit and let you know soon...

      Delete
    6. Thank you, awaiting your input

      Delete
    7. There's one circuit link provided in this article:

      http://expertscolumn.com/content/making-digital-voltmeter-ammeter-circuit-modules

      Delete
    8. Dear Swagath, I cold not fined the digital volt and amp meter. the link further takes to the another link http://easy-electronic-circuits.blogspot.in/2012/03/electronic-voltmeter-ammeter-circuit.html.

      Delete
    9. Dear Swagath, I found the link, however the circuit is not explained clearly and the connection A to F in the circuit is not explained. can you help
      http://easy-electronic-circuits.blogspot.in/2012/03/digital-voltmeter-and-ammeter-circuit.html

      Delete
    10. You can check the following link:

      http://users.otenet.gr/~athsam/digital_volt_and_ambere_meter_eng.htm

      Delete
    11. Dear Swagath, is there a circuit design for AC Amp meter

      Delete
    12. Can you elaborate a little more regarding the exact specifications.

      Delete
  7. i intend to use a digital amp meter to display current consumed in a AC line at home

    ReplyDelete
  8. Hi am new her: With PWM can attaché charger on 15v high current terminal

    ReplyDelete
  9. you are giving an external psu of 15 v, on many desulphactor there is no psu needed,is this really working

    ReplyDelete
    Replies
    1. How can a battery get charged or desulfated if there's no power suypply??

      Delete
  10. yes,you are right.Even i was wondering where will power supply come from,,,Could you tell me how to construct a trickle charger.Im designing the other pulser,,like Ron Ingrahan circuit,it appears i need a separate charger together with pulser in parrallel.Your circuit seems to be quite precise.

    ReplyDelete
    Replies
    1. Trickle charging is a process in which the battery is not allowed to discharge if its not being used for a longer period of time, it's an almost zero current charging at full charged voltage level.

      Though It will depend on the AH of the battery, typically you can connect a 10K resistor in series with a suitable charger for keeping any battery trickle charged.

      Delete
  11. If the battery is 70AH ,how will your psu be made,what type of transformer, any current ,wattage requirements?

    ReplyDelete
    Replies
    1. You can use a 10 to 15 Amp transformer for a 70 ah battery, voltage should be a little higher than the battery voltage..

      Delete
  12. HI
    Sir ..... i am interested in making desulfator,,,, can u plz help me in making it,,,, i am very curious in making a new innovation in it.... plz give me the basic concept of its designing,,, i shall be very thankful to you,,,,

    ReplyDelete
    Replies
    1. Hi,

      I have explained the concept and the circuit in the above article elaborately......

      Delete
  13. sir .. in above circuit .....is resistor 100k variable? how we set its value....
    what is given input voltage?
    sir i have simulated this circuit on proteus bt there is no output.... plz help me. how we will give voltage and type of Resistor 100k and about its value selection... and input voltage/...
    i shall be very thankful to u

    ReplyDelete
    Replies
    1. yes the resistor 100K is variable, I'll check the circuit and see if I can correct it....

      Delete
  14. hello
    please can you give the value of the inductor in H

    ReplyDelete
    Replies
    1. hello, you will have to experiment with it until you get around 18V across it...the thickness of the wire should be adequately large for supporting the battery charging current, same would be true for the transistor.....alternatively, it may be replaced with a mosfet.

      Delete
  15. thank you
    i want to desulfate a 200ah deep cycle bat. what kind of mosfet can i use ?
    i experiment with a lot of desulfetors but noone can do the job efectively
    please can you desigh a lifepo4 pcm circuit with balance i think thatis the future of the energy storage problem.
    keep on the good work
    thank you

    ReplyDelete
    Replies
    1. You may try IRF540N mosfet.

      The above circuit is also not a confirmed one, it might work or may be not, would depend on various parameters.

      Delete
  16. Greetings everyone,
    i saw this circuit and i think it is extremely practical, i'll try to do it, because i had a dead battery on my bike. but looking at the scheme and searching i don't see what is the value and type of the L1 inductor. Could you specify, please.
    also i'll try to use a microcontroller to do the pwm. I think it just have to be at the same ground, right?

    ReplyDelete
    Replies
    1. L1 will need to be experimented with, any coil which produces 18V, and is able to handle the specified charging current, would do the job....

      Delete
  17. hello
    i make this but when i connect the battery it causes .sortcircuit

    ReplyDelete
    Replies
    1. please use a diode with the positive of the battery....

      Delete
  18. Hey Swagatam,

    In general what type of pulse is most effective for de-sulfation?

    e.g. short/sharp.....hi volts....hi amps.....hi or lo freq?

    Wat do you think

    Yours
    Carl

    ReplyDelete
    Replies
    1. Hi Carl,

      As far as I know, the voltage should be slightly high than normal, but the current should be sufficiently high, and in the form of pulses.

      Regards.

      Delete
  19. Do you have any ideas on how to observe or test/measure the effects on the battery when searching for an optimum setting?

    This circuit of yours is suitable for experimentation as the 555 is so adjustable.

    It might be that having the battery in a clear case and observing the effects visually might be helpful.
    One would have to keep an eye on temp and gas production.(don't want to boil it away)

    Your thoughts.....

    Thanks for this
    Carl

    ReplyDelete
    Replies
    1. perhaps the only way to test this is to connect a virtually unresponsive battery to the circuit and set the pot to reasonably high levels, if the battery starts to accept the charge after a period of time, would prove the working the circuit.....however it's just my assumption...

      Delete
  20. Swagatam,I am absolutely sure your circuit works.

    I am trying to think of a way to observe and fine tune it for optimum.

    I'm thinking if I took a badly sulfated cell out of a battery and put it into a glass or clear plastic case along with the electrolyte, I might be able to see the action.

    What do you or your readers think?
    It's great to have a place to ask the question.

    Thanks

    Carl

    ReplyDelete
    Replies
    1. Thanks Carl, that looks a wonderful idea.

      I am sure all the readers will appreciate this approach from you.

      Delete
  21. Sir, is the pot value 5k is correct ??

    ReplyDelete
  22. One more question Sir,

    What should be the size of coil L1, i mean on how many mm it should be wind ?

    Thanks.
    Regards.

    Rashid

    ReplyDelete
    Replies
    1. you will have to experiment it by using different types of inductors, start with a 22swg wire wound over 6 inches ferrite rod having diameter of 1 cm, put around 50 turns initially and then vary it by increasing or decreasing the turns. check the output voltages across the coil without load with different number of turns..

      Delete
    2. hi, swagatam, i would like to confirm if the disulfator circuit uses an inductor coil since i don't see any in the above circuit. i'm just confused. thanks

      Delete
    3. The inductor has been removed in the present design because according to me it's not required. A desulfation process can be possibly initiated by applying high current short pulses to the battery, which can be achieved by using a high current transformer, probably equal to the battery AH level.

      Delete
  23. Hello Sir,

    Thank you for your prompt reply.
    Can i use a rounded coil which is used in computers switching power supplies ?

    ReplyDelete
    Replies
    1. Hi Rashid,

      you mean torroidal coil, yes it can be used.

      Delete
    2. ...a coil won't be required actually, please check out the updated diagram....

      Delete
  24. Hello Sir,

    I make this circuit and checked all the connections twice. It looks everything
    is fine, but I don't notice any change in battery after connected for about 10 hours.
    My battery is of 12v, 50 Amp.

    How long it will take to d-sulfate it ?

    Thanks.
    Rashid

    ReplyDelete
    Replies
    1. Hello Rashid,

      What's your AH and how much current are you using in the circuit power supply???

      Though there's no confirmed value, the current from the mosfet should be almost equal to the AH of the battery, and the pot should be adjusted to produce short bursts of output.

      Delete
  25. Sir,

    Battery is of 12v and 50 AH and power supply is giving 12v and around 2 amp. to the circuit.

    Regards.
    Rashid

    ReplyDelete
    Replies
    1. As mentioned in the article, the current should be considerably high, you should use a 40 amp transformer may be initially for testing.

      Otherwise the sulfation will not initiate.

      Delete
  26. Replies
    1. aoa Rashid. I am waqas from Pakistan. How about your experiment . Does the above recomendation solves the issue of desulfation arshad.waqas@gmail.com

      Delete
  27. hello sir... i have 12v 7Ah sla battery. what must be the input current for the above circuit to desulfation?

    ReplyDelete
  28. Thank u sir,
    Could u please let me know the way to design a battery charger using your charger concept to charge the Generator Battery.
    I mean i need to hook the charger permanently of the battery.
    Could u please reply me below email. chandanapsd@yaho.com
    Thanks advance...
    Good Luck and Highly appreciate your knowledge sharing.

    ReplyDelete
    Replies
    1. Thank you very much!

      The following link shows a more elaborate version of the above circuit, you can try it:

      http://homemadecircuitsandschematics.blogspot.in/2013/04/simple-solar-mppt-circuit-using-ic555.html

      Delete
  29. hi swagat, i thin there is some thing missing in the circuit, the inductor and couple of the commentors where mentioning about 100k resistor which i do not find in the ciruit, is this diagram correct?

    Pranav BM

    ReplyDelete
    Replies
    1. hi pranav,

      the shown circuit is a new one, the comments refer to the old circuit which has been removed by me because it had some mistakes.

      Delete
    2. thank you, you don't need the inductor?, wont it be better to add a fuse before batter and the positive power supply.

      Pranav BM

      Delete
    3. A fuse is always a welcome device for all electrical systems, so you may employ it.

      Delete
  30. Dear Swagat

    "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."

    You mean if we are desulfating a 100 AH battery you need 15V 100AH?.

    Pranav BM

    ReplyDelete
    Replies
    1. Dear Pranav,

      It's my guess only, it will depend on the condition of the battery, if you can arrange for 100amps then surely you can try it with very short pulses for a 100ah battery....again I am just assuming the current magnitude to be suitable.

      Delete
  31. 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.

    ReplyDelete
    Replies
    1. 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.

      Delete
    2. better use a 680pF for pin6/2 and 103 or 0.01uF for pin5

      Delete
    3. 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.

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

      Delete
  32. 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

    ReplyDelete
    Replies
    1. thanks electronica,

      the IC can work safely with upto 15V, yet for extra stabilization you may use a 7805 IC for it.

      Delete
  33. 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.

    ReplyDelete
    Replies
    1. Thanks Electronica,

      yes it will not be affected.

      Delete
  34. Swagatam:
    Very nice, I appreciate your attention to my queries. Best wishes from Guatemala.

    Hugo

    ReplyDelete
  35. 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..

    ReplyDelete
    Replies
    1. Hi Nawnit,

      You will need to add a delay ON timer at the output of your stabilizer as shown in the following link, a similar situation has been addressed at the bottom of the article.

      http://homemadecircuitsandschematics.blogspot.in/2013/02/make-this-simple-delay-on-circuit.html

      Delete
  36. Thanks buddy,
    will it work fine upto 4 kw load?

    ReplyDelete
    Replies
    1. You will have to select the relay appropriately, I think a 30 amp relay would do the job.

      Delete
  37. 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

    ReplyDelete
    Replies
    1. You will have to use a 24V relay in the circuit, that's all, no other change would be required.

      Delete
    2. The 24v supply for the circuit can be derived from the stabilizer board itself.

      Delete
  38. 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 .

    ReplyDelete
  39. But m not sure if it will be failed for high voltage input. Vl try to make a diagram of switching.
    Please comment.

    ReplyDelete
    Replies
    1. It's difficult to guess how it will do with high or low voltage condition, we can't say without practical testing, let's see...

      Delete
  40. 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

    ReplyDelete
    Replies
    1. Hi Nawnit,

      UHF Signal meters are complex devices, not within my reach.

      Delete
  41. @Swagatam
    Nice circuit I look forward to trying it out.
    Just one question, Where should the negative from the power supply go?
    Thank You

    ReplyDelete
    Replies
    1. Thanks!

      The negative will go to the rail which is connected to pin#1 of the IC

      Delete
    2. 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 ?
      http://2.bp.blogspot.com/-L9UBEjJp8XU/UUQLd8oW6YI/AAAAAAAADkk/FlaSh6PwIos/s1600/battery+desulfator+circuit.png

      Sean

      Delete
    3. 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.

      Delete
  42. 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).

    ReplyDelete
    Replies
    1. I wanted to keep it simple, so I eliminated the inductor part, I hope it works for you....:)

      Delete
  43. 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

    ReplyDelete
    Replies
    1. 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.

      Delete
    2. 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

      Delete
    3. 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.

      Delete
    4. 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 ?

      Delete
    5. 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.

      Delete
  44. 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.

    ReplyDelete
    Replies
    1. Hi Sean,

      Then that would be an added feature of this design.

      Looking forward to your updates...best wishes!

      Delete
  45. i am very proude of you . how can i indicate this circuit is working after design

    ReplyDelete
    Replies
    1. keep a voltmeter attached with the battry, if the voltage increases gradually within 4 hrs means it's working.

      Delete
  46. 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.

    ReplyDelete
    Replies
    1. 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?

      Delete
    2. Hi Swagatam

      Here is my basic design for LED indication of BIR status. The reference voltage is 12mV.

      https://dl.dropboxusercontent.com/u/20969135/BIR%20indicator.gif

      But, later I realized that the output is is mVAC. Any suggestions, how to deal this issue?

      Delete
    3. 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.

      Delete
    4. Hi Swagatam

      Kindly refer to my post of January 12, 2014. Here is the link for your ready reference.

      https://dl.dropboxusercontent.com/u/20969135/accutest.jpg

      The battery internal resistance is measured in mVAC. A good battery would show less than 12mVAC. And with higher internal resistance would show more than 12mVAC.

      I am just wondering how to compare the fluctuating mVAC with a reference voltage.

      Delete
    5. Hi Abu-Hafss,
      I think it would be a better idea to use a LM3915 IC for detecting the relevant voltage levels because the opamp circuit could become too complex.
      Refer to the last diagram in the following article, the mic can be removed and the transistor may be directly fed from the 100k pot output

      http://homemadecircuitsandschematics.blogspot.in/2012/03/how-to-make-vibration-detectormeter.html

      Delete
  47. Hi Swagatam

    I came across a desulfator circuit which, apart from the regular desulfation process, also shorts momentarily battery terminals as shown here:

    https://dl.dropboxusercontent.com/u/20969135/Desulfation.gif

    I want to know, couldn't the signal from the 555 pin#3 be directly fed to the gate of the mosfet (point A) or at point B?

    ReplyDelete
    Replies
    1. Hi Abu-Hafss,

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

      Delete
  48. 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.

    ReplyDelete
    Replies
    1. 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

      Delete
  49. 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.

    ReplyDelete
    Replies
    1. 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.

      Delete
  50. 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

    ReplyDelete
    Replies
    1. Hello Carl,

      Please see the last diagram in the following link, it'll fit your need well:

      http://homemadecircuitsandschematics.blogspot.in/2011/12/how-to-make-simple-low-battery-voltage.html

      The second relay shown is not relevant, you may remove it.

      Delete
  51. 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.

    ReplyDelete
  52. 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?

    ReplyDelete
    Replies
    1. The line connected with pin#1 of the IC is the negative line and must be connected with the power supply negative.

      Delete
    2. 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

      Delete
  53. 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.

    ReplyDelete

Readers are requested not to include external links while commenting. For consulting a diagram, upload it on Google Drive and provide the link here.