Battery Desulfator (with resonant frequency detector and locker)

Discussion in 'The Projects Forum' started by Satan, May 19, 2009.

  1. Satan

    Thread Starter New Member

    May 19, 2009
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    Hi

    I am currently building a lead-acid battery desulfator. The basic circuit has been done. It utilizes pulse current to desulfate the sulfation of the battery at its resonant frequency.

    I am thinking of adding a frequency sweeper to the circuit so that it can scan, detect and lock-in to the resonant frequency automatically. Then the circuit will generate pulses at this 'new' resonant frequency. To implement this, I am thinking of using 4046 PLL as the resonant frequency detector and locker, driven by a PIC microcontroller. Even though I have this idea, but I am still quite confused on which part to start first.

    Is this idea visible? How should I go about it?


    Thanks
     
  2. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    Resonate frequency of what? How does it affect the chemistry?

    john
     
  3. SgtWookie

    Expert

    Jul 17, 2007
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    Post a schematic of your circuit.
     
  4. Satan

    Thread Starter New Member

    May 19, 2009
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    Resonant frequency of the sulphate crystals in the lead-acid batteries.
     
  5. Satan

    Thread Starter New Member

    May 19, 2009
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    The basic circuit closely resembles the one proposed by Ron Ingraham, using an N-channel mosfet instead of a P-channel.

    As for the PLL and PIC, I have not really constructed them yet, just had this idea in my head and I still haven't figured out yet how and where to start. But roughly, I have this in mind:

    PIC --> 4046 PLL --> Desulfator --> PIC (back to PIC again as this output will be 'modified' according to the resonant frequency of the sulphate crystals in the LA battery).
     
  6. Papabravo

    Expert

    Feb 24, 2006
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    In your opinion what is the relevance of this alleged resonant frequency on the chemical processes going on? The reason that I ask is that I think someone has sold you a bill of goods. Maybe you would be good enough to post a reference to some work on this subject.

    It might also be reasonable to ask if you have any clue about the approximate range of this alleged resonant frequency.
     
  7. Satan

    Thread Starter New Member

    May 19, 2009
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    Some useful links:
    www.alton-moore.net/graphics/desulfator.pdf
    http://www.instructables.com/id/Desulfator_for_12V_Car_Batteries_in_an_Altoids_Ti/
    ilbcnu.org/file_share/leadacidbatterydesulfationpulsegener.pdf

    At the resonant frequency, the sulphate crystals will have the weakest bond among them, so by applying pulse current at their resonant frequency, it is easier to break them and to dissolve them in the electrolyte.

    From many sources on the internet, it seems that the frequency range is from 2 to 6 MHz.
     
  8. beenthere

    Retired Moderator

    Apr 20, 2004
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    Not quite so. www.enviroharvest.ca has an article on desulphation which states, in part -
    800 KHz and 2 - 6 MHz are a long way apart. Most chemical compounds have resonant frequencies related to the size of the molecule. They tend to be at frequencies in the IR range.

    I would be more inclined to follow up on the 800 KHz frequency - the explanation of the effect is more likely. I question any resonant effect, though.
     
    Last edited: May 19, 2009
  9. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    For starters, I would be suspicious of any claim regarding sulfides -- think of hydrogen sulfide (H2S) -- in a lead-acid battery and the oxidation of such sulfides to sulfates as part of a rejuvenation process. I have no idea what the author means by "recombining" the crushed sulfides (if they exist) with the sulfuric acid in the electrolyte. Remember, the specific gravity is very low in a sulfated battery, because the sulfuric acid concentration is also quite low.

    On the positive side, mechanical agitation of solids can facilitate reactions by exposing greater surface area. It is not resonance in sense in which such resonance was proposed by the OP.

    However, mechanically removing the sulfate and adding more sulfuric acid may cause a dead battery to retain a small charge, but will not fully rejuvenate a dead battery to a useful capacity.

    John
     
  10. Satan

    Thread Starter New Member

    May 19, 2009
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    Then how? How should I go about it?
     
  11. Papabravo

    Expert

    Feb 24, 2006
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    Stop for a moment and ask yourself how much time and money you are willing to part with, before anger and frustration at having been hornswoggled the practitioners of techno-bumpf sets in. This is the opportunity cost of continuing on your present course. Then ask yourself if there are other ways to spend that time and money that would give you equal or greater satisfaction.

    I'm a graduate engineer, and I found no credible information on any of those links.
     
    Last edited: May 21, 2009
  12. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    I had written a response earlier this morning echoing Papabravo's sentiments that got lost in my pop-up blocker when I did spellcheck. I'm just a chemist, not an engineer. From that standpoint, the chemistry of what you want to do won't work.

    On the other hand, you will find this forum extremely helpful for electronic projects that are doable and even some that aren't. Aside from the desulfator, what sort of projects interest you?

    John
     
  13. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    I'm interested in your input as a chemist. I knew that the whole concept of "resonance freq" of the sulphate crystal was bunkum, but I have heard that desulphaters do work based on the pulse charging and general agitation of putting AC current into a battery.

    It was also common many years ago to have battery chargers that ran on pulsed DC, usually 100Hz or 120Hz (from the mains) I have a 1950's (or '60's?) battery charger here that does just that (it has no capacitor after the rectifier). I'd heard from the "old-timers" in the steelworks where I worked in 1981 that these old pulsed DC battery chargers were better than the "new fangled" pure DC ones for charging batteries and better to rejuvenate tired batteries based on being pulsed rather than pure DC.

    I have rejuvenated some lead acid batteries my self by applying load and charge cycles and always assumed a higher freq AC current into the battery does basically the same thing.

    Can you provide any input on this?
     
  14. HarveyH42

    Active Member

    Jul 22, 2007
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    I don't think the sulfate/sulfide crystals go back into solution, mostly get vibrated loose from the plates, and deposit on the bottom. Clean plates should restore some capacity, but probably won't stay that way for long.
     
  15. CptBriGuy

    New Member

    Jun 24, 2014
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    I have a couple of homebrew HI POWER Desulfators I will give away for the cost of shipping if anyone wants to try them out.
     
  16. alfacliff

    Well-Known Member

    Dec 13, 2013
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    how much nigh frequency vibration can you get from a battery? puls desulfators work by providing high (higher than normal charging) voltage pulses to charge the battery. they do not resonate anything, they are pulsed so they dont build up bubbles of gas on the plates which would slow the charging process.
    a locas test equipment manufacturer, hit with high costs of replacing gel cell battery packs went to half wave rectified charging current instead of rectified and filtered current, and the battery life increased drasticly.
     
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