12 Volt Lead Acid Battery Desulfator

Discussion in 'General Electronics Chat' started by Joster, Sep 9, 2014.

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  1. Joster

    Thread Starter Member

    Jun 12, 2013
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    Hi All,

    I'm looking for a good schematic for a 12V lead acid battery desulfator. Anyone one have one kicking around..I know there are lots on google but looking for one that some one else has built and had good luck with.

    Thanks!

    Joe
     
  2. Lestraveled

    Well-Known Member

    May 19, 2014
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    I am trying to respond to your request but the forum will not let me post a schematic.
     
  3. Lestraveled

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    May 19, 2014
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    I used to post a lot at the "Lead Acid Battery Desulfator" forum under the the name, "Tucsonshooter". I have some designs that are well proven.

    The forum still will not allow me to upload a file.
     
  4. Joster

    Thread Starter Member

    Jun 12, 2013
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    great thanks a ton ill check out that thread
     
  5. ScottWang

    Moderator

    Aug 23, 2012
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    What happened to you, I just uploaded a file normally.
     
  6. ScottWang

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    Aug 23, 2012
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  7. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Joster,

    Save your time and money. Desulphation is a useful way of extending lead acid battery life, but "pulsing" the battery with energy stored in an inductor has nothing to do with that. Pulsing just momentarily forces the terminal voltage of the battery to a region where some benefit occurs due to the overvoltage. This is called "equalization". A DC power supply does it just as well as the 555 circuits with an inductor (primitive switch mode voltage boost circuit)

    All of the testimonials to the contrary are pure bs, just like OverUnity...
     
  8. MrAl

    Well-Known Member

    Jun 17, 2014
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    Hi,

    MikeML:
    Where are you getting your information from? I was wondering about this too because i built a "desulfator" too a long time ago and it did not do that much at all, maybe a little that's about it. If you have any references i'd really like to read them. Thanks :)
     
  9. MikeML

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    Oct 2, 2009
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    Read the stuff on Battery University I linked to. I have done some comparitive experiments where I "pulsed" one time, and "equalized" the next. If a battery needs equalization, doing it using a constant-current charger wins hands down... The "benefits" claimed by the "pulsing religion" can be achieved faster by simply DC charging, or DC equalization, if the battery is badly abused.
     
  10. Lestraveled

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    May 19, 2014
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    Here is a basic schematic for a desulfator I designed when I posted (lived) at the Lead Acid Battery Desulfator forum. It was designed to use capacitors as the energy storage devices. The inductors are just there to charge the capacitors. General purpose electrolytic capacitors will yield an output of 30 to 50 amps. If you use low ESR caps then it will easily output 100 amps.

    [​IMG]


    I fully agree with MikeML about the inductor based desulfators. They are generally too low power to repair a sulfated battery.
     
  11. MikeML

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    Oct 2, 2009
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    My point is that if a battery needs "equalization", then a DC current of ~1A per 35AH of battery capacity does it better than any PWM circuit, regardless if the energy storage is in a capacitor or inductor.

    btw- the benefits of equalizing lead-acid batteries has been known since Ford began selling the Model A.
     
  12. Lestraveled

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    The down side of equalization is heat, the healthier cells will have a higher voltage and will dissipate more heat than the weaker cells. The older the battery, the worse the heat will effect it. Equalization is a good way of making a older moderately performing battery into a dead battery because of a warped plate. Pulse equalization/desulfation does away with the heat issue. Also you get the benefit of capacitive voltage division that helps equalize the voltage across each cell. ( A battery cell has the same construction as an electrolytic capacitor.)

    btw - Back when Ford was selling the Model A, they did not have Mosfets with single digit Ron resistances and ultra low ESR electrolytic capacitors, which are essential for high powered desulfators.
     
  13. MikeML

    AAC Fanatic!

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    If you limit the equalization current to 1A per 35Ah of battery capacity, or 3A for a 100Ah battery, heat is never an issue... I have equalized hundreds of batteries thousands of times using just a constant-current DC supply with never a warped plate.

    Not every equalization will recover a worn-out battery, but equalizing flooded-cell batteries in little-used vehicles (golf carts, airplanes, boats, RVs, etc) will greatly extend the useful life of the batteries. I routinely get 5 to 7 years on batteries that otherwise would need replacement every two to three years in Arizona's hot weather.
     
  14. Lestraveled

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    I don't know where you got 1 amp per 35Ah number from. The recommended charge rate for most flooded batteries is 10% of C, (C = Ah rating). At 1 amp per 35Ah or 3% of C you could not get most batteries to up to absorption termination voltage let alone raise it to the equalization voltage.
     
  15. MikeML

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    Assuming a typical 65Ah starting battery is already fully-charged, driving 2A constant-current through it will get the terminal voltage up to 16+V in a couple of hours. A typical equalization cycle is ~8h, during which the cells bubble lightly.

    The primary benefits from this controlled overcharge come from the rising bubbles stirring stratified acid. Driving the reaction to gas evolution raises the Specific Gravity (acid concentration) in all cells. A high S.G. dissolves Lead Sulphate.

    You should not do this to AGMs. You can do it very occasionally to SLAs with some benefit. Flooded cells where you can add water can be equalized ~ every six months...
     
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  16. Lestraveled

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    May 19, 2014
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    MikeML
    I agree with what you have said except on the charge current. Even starting verses deep-cycle batteries, the difference in charge current is not that much. 2 amps is the standard charge rate for a motorcycle battery. 10 amps for a car battery. 20 amps for a Trojan or a Crown deep-cycle RV battery.
     
  17. MikeML

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    I said nothing about charging current. I am talking ab0ut the current that flows into the battery only during the "equalization" cycle. Most starting batteries will accept the entire output of the alternator (35A to 65A) during charging. Charging limits like 0.25C apply mostly to sealed batteries.
     
  18. Lestraveled

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    Do you think the current required to reach, and hold at, the equalization voltage, is less than the current required to charge it? ....................
     
  19. MikeML

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    Yes, by an order of magnitude... Take a previously fully-charged 12V battery. Connect a lab power supply with the voltage limit set to 20V or higher, set the current limit to 2.0A, connect across battery. Measure battery terminal voltage 2 hours or more hence. Voltage will climb to >16V. Equalization is what happens while battery voltage is >2.6V per cell (15.6V for a six cell battery)

    If the battery is not fully-charged to begin with, with a 2A (low) constant-current charge rate, the battery terminal voltage will stay below 2.4V per cell for a long time, and then climb upwards toward 2.65Vpc after the charging chemical reactions are over....

    Figure 6 in this link shows this behavior. The reactions take longer with a smaller charging currents, but the voltage vs time curve keeps its shape. I just recharged the 200Ah battery in my motor home using a 1.5A charger. Why did I do this? Because I didn't care that it took four days to recharge the battery, as I knew I wouldn't be needing the motor home for several more days...
     
    Last edited: Sep 10, 2014
  20. Lestraveled

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    May 19, 2014
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    There is a huge difference between a starting battery, a deep cycle battery, and a really good deep cycle battery. I suspect you have been talking about starting batteries only. In my opinion, when it come to starting batteries, there is very little to talk about. They are tailored to live in your car, start your engine, and be charged by your alternator and then die quickly. They fit your 2 amp charging profile. I don't mess around with these batteries.

    The batteries I deal with, people live on. I live on them. We dry camp all the time. (We are Duners.)

    Anyway, here is a picture of two Trojan T105 batteries that were given to me (as dead). After working them, desulfating/equalizing, they now read 12.7 volts and show 80% of capacity on a discharge test. I expect to get 2 to 3 years of life out of them.


    [​IMG]
     
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