36 volt desulfator

Discussion in 'The Projects Forum' started by BrainFog, Jan 26, 2011.

  1. BrainFog

    Thread Starter Member

    Jan 24, 2011
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    Hello everyone. I am fairly new to, but very interested in, electronics and how they work. All my life I have enjoyed taking machines apart and being able to understand how and why they work but have always lacked an in depth knowledge. I would also like to learn how to design and build my own. I am going to use this as an excuse to introduce myself to building more complex circuits. In the past I have made a few basic LED circuits connected to power supplies in order to light my aquarium and have learned a surprising amount from them such as how the slightest change in voltage can have drastic affects on wavelength, power consumption and to a lesser extend brightness. I have a 36v battery pack containing 3 12v gel lead acid batteries (for my purpose I must use gel batteries) and before decided to go down the desulfating path I considered buying these as a replacement: http://cgi.ebay.co.uk/NP7-12-12v-7A...rElectronics_Batteries_SM&hash=item19bf71fec3 They are practically identical apart from the fact that they are made by a different company and mine are 8AH not 7. I am not sure how relevant most of this is but I am attempting to be thorough. The batteries I am desulfating (inside the battery pack) are each producing about 12.8v after being fully charged and the voltage they produce is in no way a problem but the low amps per hour are. I have looked online and although a few companies sell 12 and 24 volt desulfators and desulfator kits I have found no 36v ones in the UK. Not to mention being unable to find a trace of a schematic for a 36v one. Most of the schematics I have found use a 555 chip which appears to be designed to create timed pulses which does appear to be what a desulfator does anyway. I am sure the 12v desulfator design can be easily modified to the 36v design but I simply do not know how and have had no luck in finding out how online. 1) How would I go about designing and building my 36v desulfator? 2) Would it be safe to build one into an extension cable between the charger and battery? 3) Does anybody know any good parts sellers in the UK apart from the ones on Ebay? 4) Does anybody have first hand experience with any negative effects caused by desulfators? Thank you
     
  2. BrainFog

    Thread Starter Member

    Jan 24, 2011
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    Oh the spacing and paragraphs seem to have vanished from my thread. How do I fix this?
     
  3. Gundalf

    New Member

    Jun 22, 2010
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    If you are talking about hard sulphation caused by letting batteries go flat, you would be better off buying new batteries. It's not really possible to recover heavily sulphated batteries once crystalline deposites have started to form.
     
  4. SgtWookie

    Expert

    Jul 17, 2007
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    I beg to differ with Gundalf; I've successfully used a desulfator to revive a heavily sulfated lead-acid riding lawnmower battery (three cells had a specific gravity of 1; or just plain water) to serviceable status. It took about 6 weeks, but it worked.

    The batteries you are/were considering are not gel-cel; they are AGM (absorbent glass mat) batteries.
    Datasheet: http://www.yuasabatteries.com/pdfs/NP_7_12_DataSheet.pdf
    AGM batteries are preferable to gel cel; they can be used in any orientation, will not spill acid if the housing is breached, and don't have the drawback of gel cells in that overcharging gel cells will form permanent bubbles in the gel that reduce battery capacity; there is not a good way to eliminate the bubbles.

    Rather than attempting to build a 36v desulphator, you could use three 12v desulfators, one per battery - either that, or remove them from the item they are powering and desulfate them one at a time.

    It'll be difficult to design/build a 36v desulfator unless you have test equipment like an O-scope, 60MHz bandwidth or higher.

    Also, the typical spike output of a 12v desulfator is around 60v when you first start the process. If you're trying to desulfate three heavily sulfated batteries in series, you'd need around 180v peak.
     
  5. SgtWookie

    Expert

    Jul 17, 2007
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    Click the "Edit" button right below your original post.

    Place your cursor where you'd like to make a new paragraph, and just hit the Enter key a couple of times.

    I prefer for people to not use fonts and colors, as it makes replying with quotes quite difficult due to the great number of embedded vBulletin codes that are generated.
     
  6. Gundalf

    New Member

    Jun 22, 2010
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    In that situation I rather suspect you didn't have a hard sulphated cell - just a high resistance one (as evidenced by the fact it was just pure water more or less in it). What I mean by sulphation is a cell that holds it's volts, is down a little on heavy amps, and is very down on capacity. One that is just flat, and is so flat it wont properly charge is what people tend to call sulphated but in actuality they just want either a dose of acid to get them to start charging (and correction of pH later) or they need a high voltage to force a trickle current through. I usually just give them directly rectified mains current through a small fuse and wait for the current to climb and blow the 200mA fuse then a regular charge (I have a large bag of these fuses so it's the easiest way)

    Most of the high voltage pulse ones will recover deeply discharged batteries with high resistance cells, but these batteries are not sulphated with crystalline deposits, they have the amorphous deposits that form normally. Trying to recover crystalline ones is impossible as the reaction kinetics and energetics are against you doing so.
     
  7. SgtWookie

    Expert

    Jul 17, 2007
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    As I stated above, the hydrometer indicated a specific gravity of 1, or pure water. The battery was a Yuasa that had a semi-translucent case. I could easily see heavy yellow-whitish deposits on the plates. The electrolyte level was low when I obtained the battery, and added distilled water until the plates were covered. A gentle agitation (rocking from side to side) ensured that the water was well-mixed with whatever electrolyte was left.

    During the desulfating process, I monitored the rise in specific gravity; it took 5 to 6 weeks for it to reach at least 1.260 and restore the battery performance. No acid was added or removed.

    I would not recommend adding acid, as that removes the ability to determine when the cell is completely desulfated. When the battery was originally delivered, the specfic gravity was correct when the battery was fully charged. If the specific gravity is low, that means the cell is discharged and/or the plates are sulfated.

    The original poster stated that their batteries are gel cel, and therefore they cannot change the electrolyte. They may be in error; the batteries might actually be AGM - but you can't do much about that electrolyte either.

    We will not recommend such a procedure, as it is dangerous.

    Have you ever attempted using a desulfator?

    I am not saying that they will work in all cases. This was a single battery that I restored. If the cells are shorted internally or badly decayed, there is nothing one can do to fix them.
     
  8. Gundalf

    New Member

    Jun 22, 2010
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    I spent 6 months at Uni looking into desulphation methods and have cut up more batteries than I care to remember. From what you said with the sg at 1 you would essnetially have had pure water - that doesnt sound at all like a battery that has been sulphated as these usually stop with some acid left in the electrolyte. More like the cell has either been reversed or was low on acid content in the first place in which case a high voltage will obviously help to recharge it.

    As for the royal we - well I would have to differ. If that's not acceptable then I guess I won't post up any of the stuff I was about to about building things from the mains if that's unacceptable.
     
  9. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    Here's what the US DOE has to say about sulfation. We spent billions to get this little pearl, so it must be true. :D

    http://www.hss.doe.gov/nuclearsafety/ns/techstds/standard/hdbk1084/hdbk1084.pdf

    The issue is big crystals separated from the lead grid vs. amorphous stuff. Big crystals are not going to reform spongy lead.

    John
     
  10. BrainFog

    Thread Starter Member

    Jan 24, 2011
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    Thank you for your replies.

    The edit button seems to be missing, I could swear I saw it shortly after the original post. Lets hope that this one stays in paragraphs rather than being turned into a block of text like the last one.

    I have disassembled the battery pack (which takes a little while and also means I can not leave the batteries in as I work on them) and the information on the side of them reads: MICROLYTE "Red Top" -MRT CYCLIC BATTERY SEC 12MRT8-12Volt 8AH. It is an interesting fact I mistakenly thought AGM was simply a company that made them and they were all gel cells, well at least that is what I was told. I am glad I know now.

    Seeing as the 12v design is so well tested it may be the best place to start for me but I still have quite a few questions about it.

    I am going on the fact that i have read that it is very important to charge the batteries during the desulfation process.

    Apart from convenience one of the reasons I was hoping to desulfate my batteries while attached to the 36which is designed to prevent overcharging which to my knowledge damages to battery. If they are AGMs will this be a problem if I overcharge them on a 12volt charger without overcharge protection while desulfating?

    Is it in fact a good idea to connect the desulfator to a mains charger as I read yesterday that this can cause problems with the homes other electrical items as the pulses would go through the charger into the wall socket as well?

    Would it be possible if I do go down the path of using a 12 volt desulfator to connect all 3 batteries in parallel to the desulfator?

    I am wondering about the limitations of connecting items in series are and why? I am wondering as quite a bit of concern was shown over 180v pulses potentially being required.
     
  11. SgtWookie

    Expert

    Jul 17, 2007
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    Interesting. Perhaps your browsers' cache is full or damaged? Try emptying the cache and deleting your cookies and history.

    I can't seem to locate a datasheet in English for the 12MRT8; it appears that they are all in Japanese. However, from one sales website that gives some specifications in English, it is a VRLA (Valve Regulated Lead Acid) battery. Another site categorizes the battery under "Sealed cell, lead acid batteries with pressure release vents."

    However, that alone does not differentiate between gel cells and AGM batteries, and I don't seem to be able to determine what your batteries are; they could be either. Perhaps someone who can read Japanese datasheets will find one and tell us what they are?
    See this Wikipedia entry:
    http://en.wikipedia.org/wiki/VRLA_battery

    AGM is relatively new; I'm not certain when manufacturers started making VRLA batteries AGM, but at least 3-4 years ago.

    The desulfator unit draws some current; it isn't 100% efficient. Allowing the battery to become discharged will be counterproductive, as will overcharging it.

    You should not use an automotive-type charger on these batteries, if that's what you are thinking. If the batteries are partially to fully discharged, the bulk charge rate should not exceed C/5 for AGM batteries (C/3 in some cases), which is about 1.5A (C/5 rate) for a 7.5AH battery (which is what yours seem to be, even though there is an '8' in the part number). There is a bit of a difference in the termination voltage for the bulk charge. However, you could "float charge" either at between 13.4v and 13.8v, as long as the maximum charge current is limited.

    You wouldn't want to connect a charger directly in parallel on a battery with a desulfator, as the HV spikes could cause problems with the chargers' output stage. In a desulfator that I built, a float charger is connected at the junction of the two inductors, where virtually none of the HV spike gets to.

    My desulfator is not the same as Alistair Coupers (the original), which uses a P-channel MOSFET. His design is in this PDF:
    http://alton-moore.net/graphics/desulfator.pdf
    To add a trickle charger, connect it across C4, positive on the top. There will be some ripple voltage on C4, but not a lot.

    The version I built uses an N-channel MOSFET; basically the circuit is flipped upside-down from Alistair's design. There's more to it than that, but I'm just trying to keep things simple.

    You'd want to make certain that they were all close to the same voltage before connecting them, otherwise very high currents could flow between them causing high power dissipation in the batteries and/or interconnecting wiring.

    You'll also want to make certain that none of the batteries have shorted cells. Let them charge up completely in your 36v charger, then remove/disconnect them from the charger and let them sit for 12 hours before measuring their voltage with no load on them. If any of them measure below ~10.7v, one or more cells are likely shorted internally and desulfating probably won't help them.

    If a battery has a shorted cell and is charged in series with other batteries, the shorted cell will cause overcharging of the remaining good cells in the string, causing them to deteriorate much more rapidly than if they had the proper charging voltage. AGM and gel cells do not tolerate overcharging well at all. The failure of one battery will rapidly result in the failure of all of the batteries.

    If you are charging them in parallel, the one (or more) battery/batteries with shorted cell(s) will pull down the float voltage for the remaining good cells. Undercharging is about as bad as overcharging, but overcharging will probably kill them faster.

    You would need more capable inductors and MOSFETs than shown in the original schematic, and the timing would need to change.

    Have to run...
     
    Last edited: Jan 28, 2011
  12. BrainFog

    Thread Starter Member

    Jan 24, 2011
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    Turned out that the block of text problem was because I forgot to tell no-script, a Firefox browser security add-on, that this site is safe.

    Thank you very much for your help sgt wookie.

    After looking around I finally managed to find a site that clearly confirmed the batteries as Absorbed Glass Matt batteries.

    Just to confirm, it will not cause any damage or problems to leave a charged battery on a float charge of 13.5v (float charge stated on the battery) even when fully charged?

    I did consider connecting it to a solar panel but after a little research realised that they only really work in countries that experience something called sunny days. hehe The charger I was considering due to its low amps was this one: http://cgi.ebay.co.uk/300mA-charger...rElectronics_Batteries_SM&hash=item19c1054104
    Although I have now noticed that it claims a 12v output which may be a mistake.More research is needed or I could try making my own power supply, they seem simple enough. What do you think?

    Aftering cecking that the 3 batteries are fully charged I left them for about a day and did individual voltage checks and they were: 12.73v 12.74v 12.73v. So I have no shorted cells and can safely use them in parallel.

    What are the differences between 555 mosfet and a pic based desulfators?

    I have begun searching for the parts I need and although I could not find ones that are exactly the same as stated in the pdf link I have found some that appear to be the same. Just to confirm that these are correct:
    http://cgi.ebay.co.uk/10-x-555-time...al_Components_Supplies_ET&hash=item43a489a499
    http://cgi.ebay.co.uk/5x-BYV72-100-...al_Components_Supplies_ET&hash=item20b5ad3dc5
    http://cgi.ebay.co.uk/IRF9540-IRF95...al_Components_Supplies_ET&hash=item2a0d2d311b

    I have had a bit of trouble finding "L1 220 µH (nominal) Ferrite inductor 6+" A peak. Would a 220uH Radial Inductor 0.9A be suitable?

    Similar problem with finding: L2 1000 µH Ferrite choke, 100 mA; but I will leave that for now.

    Thank you
     
  13. SgtWookie

    Expert

    Jul 17, 2007
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    Glad you figured that one out. :)

    OK, good.

    Correct. Have a look at this post I made in the "Tips & Tricks" thread in the General Electronics Chat forum:
    http://forum.allaboutcircuits.com/showpost.php?p=262143&postcount=38
    View the spreadsheet image.

    LOL! I've heard that about the UK.

    Building a simple linear power supply is not difficult. However, you might ask the E-bay seller if the maximum output voltage is regulated and what the terminal voltage is of their charger, or is it not regulated?

    OK, good. Did you happen to measure their voltage when they were connected to your charging unit?

    Very generally, the PIC-based desulfators are digital and the uC requires programming; the 555-based desulfators are analog and can be "programmed" for frequency and duty cycle by changing resistors. If you go the PIC route, you'll need to either purchase a pre-programmed uC, or build/buy a PIC programmer, along with learning how to program it. The 555 based desulfator does not require that learning curve.

    Well, the NE555's and IRF9540 are fine. The rectifier will work, but it's maximum overkill.

    No. I suggest toroidal (donut-shaped) inductors, as they will generate far less RFI than radial or axial inductors. In toroidal inductors, virtually all of the magnetic energy stays within the toroid. You may need to wind your own; this is not difficult to do. Locating a supplier of suitable ferrite cores might be probematic; RS Components might carry them, but I don't have time to look at the moment.

    Adding a float charger will increase the DC level through L2, so I suggest an L2 inductor rated for 2A.
     
  14. SgtWookie

    Expert

    Jul 17, 2007
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  15. BrainFog

    Thread Starter Member

    Jan 24, 2011
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    No the batteries were not connected to the charger in any way; they were not connected to anything and had not been for at least 18 hours. Is there a problem?

    The diodes are high amp aren't they, I will look around for lower amp ones.

    As for the inductors, in the first post I stated how I have always enjoyed taking machines apart particularly as a child. Seeing as I tend to keep anything I think may be useful and me being a child was not very long ago I still have quite a few parts and PCBs stored away. Among the piles of capacitors I broke getting off PCBs (some were in OK condition and some could even be used for this but as they are cheap I will get new ones) I found a few parts that may be useful:
    [​IMG]
    Most do not have clear markings but I do have a few ferrite cores there and plenty of wire all of varying sizes. How do I find out what length and thickness of wire to use? Also should they be wound round in any particular way for certain purposes?

    Thank you
     
  16. BrainFog

    Thread Starter Member

    Jan 24, 2011
    122
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    Just to confirm, I am very drained and forgot earlier. The blue things in the photo are ceramic capacitors and 0.022uF = 22nF and 0.047uF = 47nF?

    Also would it be worth adding a fuse or diode to protect it if I incorrectly connect it to the battery?

    What is the part called that you solder to the PCB and then slot the 555 into?
     
    Last edited: Jan 30, 2011
  17. SgtWookie

    Expert

    Jul 17, 2007
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    No, no problem. It would've been interesting to know what the "float voltage" was in the apparatus that you used to charge them though.

    Those you found would work; it's just that they would be a bit large physically..

    I did too. When I was about 11 or 12, I asked my Dad if I could have an old tube/valve radio that hadn't been used in a good while, and he said OK. However, he was not expecting that I would completely dismantle it, snipping all of the components and tube sockets out - he was a bit put out by that, but I made amends when I used some of the parts to repair another radio that he DID use regularly which had gone "on the blink".

    Those toroids you have there look promising; particularly the yellow ones. They likely came out of defunct switching power supplies (like old computer power supplies.)

    What are their dimensions, best as you can measure? Need the outside diameter, inside diameter, and thickness; inches or mm's please.

    Do you have an oscilloscope, or access to one?

    Failing that, do you have a meter that reads inductance or frequency?

    I see that.

    For thickness, AWG-22 is sufficient for up to around 7 Amperes on toroids and short runs. As far as length, that depends upon how many turns will be required on your donuts/toroids.

    A VERY handy and free software package for toroidal inductor calculations is available here:
    http://www.dl5swb.de/html/mini_ring_core_calculator.htm

    Ronald Dekker has a very interesting site, here:
    http://dos4ever.com/
    In particular interest to you is his "Flyback Converter for Dummies" page:
    http://dos4ever.com/flyback/flyback.html
    ...and the "What you need to know about inductors" section; then scroll down to the "An inductor test bench" section.

    You may find the "Boost converter" section of interest, as it's closely related to the desulfator project - but instead of outputting pulses, his boost converter simply outputs a high DC voltage level. If you wish to try building these circuits, I suggest you reduce resistor R4 to under 47k in order to keep the maximum voltage in more safe territory.

    Well, it helps to be reasonably consistent in how you wind them. For this project, it doesn't really matter which direction you wind them. I usually hold the toroid in my left hand, passing the wire down through the center with my right, making certain that I don't pass the wire under a previous wind. Making a "knot" like that tends to kill the Q (quality factor) of the resulting inductor.

    One "turn" of wire = 1 pass through the center of the toroid.

    10 turns is about the minimum number of windings to get reasonable approximation of the AL value. With some toroids (depending on the material used) many more turns are required. Toroids are rather brittle, so handle them with a reasonable amount of care, and try to not drop them on a hard surface.

    Here is a convenient toroid winding tutorial page:
    http://www.kitsandparts.com/howtowindtoroidswithoutpain.php

    Note that in the tutorial, he winds the turns on in one section of the toroid, and then spreads the turns evenly about the toroid. I prefer to wind the turns on evenly to start out with. If you have the turns all bunched up on one side, it tends to increase the inductance at the expense of the Q.
     
  18. BrainFog

    Thread Starter Member

    Jan 24, 2011
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    I have been mostly familiarising myself with inductors over the last few days and reading up on them has opened up quite a few questions. Do not worry I will not overload you with them and you do not have to answer them I am simply curious.

    Some that I have are:

    Why are the toroid inductors so much less common than the radial or axial inductors? Although I have found little mention that toroidal inductors are superior it does stand to reason with the nature of magnetic fields that they would cause less magnetic distortions. I wonder if it is more to do with price due to the difficulty of winding the wire. What kinds of problems would be caused if do use radial or axial inductors?

    I have noticed that some 1000uh inductors have only a few passes where as others have 100s why is this?

    What is the differance between low impedance electrolytic capacitors and normal electrolytic capacitors and how does that affect the circuits?

    And onto what is more relevant to my project:

    The toroids I have which are mostly yellow with white at the base measure: one with no wire; od 25mm id 14mm T 8mm (10mm), smaller one covered in approx .3mm wire; od 18mm id 16mm t 8mm (10mm), larger one with varying sizes of wire; od 26mm id 15mm t 10mm (12mm), covered in black rubber sleeve; od 23mm id 16mm t 7mm (9mm). Small black toroid od 16mm id 12mm d 7mm (8mm). The numbers in brackets include the diameter if I include the slight curve that budges outwards.

    Are ferrite inductors and choke coils the same thing? And does 6+ A peak mean greater that 6 amps at peak?

    I do not own or have access to an oscilloscope or something that reads reads inductance or frequency, all I have is a standard multimeter which reads dc voltage, ac voltage, amps and resistance. I have seen items like this on ebay: http://cgi.ebay.co.uk/LCR-RCL-INDUC..._Measurement_Equipment_ET&hash=item1c15cac755 is this the sort of thing I really require?

    Would it be worth adding a fuse to protect my desulfator incase I mistakenly hook it up incorrectly?

    What is the part called that you solder to the pcb then slot the 555 into? I have read that they can be very sensitive to heat.

    Thank you once again for your help.
     
  19. SgtWookie

    Expert

    Jul 17, 2007
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    Cost of manufacturing is a major reason. It's very simple to wind a radial or axial inductor compared to a toroid.
    Another reason is board space; toroids tend to take up a fair amount of real estate.
    However, with toroidal inductors, almost all of the field stays in the core, so emissions are very low in comparison to axial or radial inductors; generally no shielding is required.

    Different core materials used that have different permeability & max flux density, different core sizes.

    It affects how rapidly the caps can be charged and discharged without overheating. If the electrolyte boils, they'll pop open. You can use several smaller standard electrolytics in parallel to effectively reduce ESR.

    OK, but you'll need some way to test their inductance. I'm not firing on all cylinders at the moment, so I'll have to come back to this later.

    They are both inductors. Chokes are generally intended to supply current while isolating a power supply from a "noisy" circuit; sort of a sub-classification of "inductor". The 1,000uF inductor could be considered a "choke".

    Yes. Basically, they're trying to avoid saturation of the inductor. See Ronald Dekker's page I linked to before as to what happens when an inductor saturates.

    That would be an easy and inexpensive way to measure your inductors and caps. Getting all that functionality for ~$18USD delivered is quite a bargain.

    Yes. 2A should be adequate protection.

    DIP IC sockets. The machined pin type are far superior to the stamped sockets. You really don't have to use them, unless you wish to be able to remove the 555 timer without a soldering iron.
     
  20. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    They are also handy if you are not sure if the IC will survive your soldering ;)
     
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