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Lead Acid Battery Desulfator

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by wasrana, Aug 21, 2008.

  1. wasrana

    wasrana New Member

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    Hi,

    I'm looking to built this desulfator.


    Is is worth making?

    Secondly i can't find the inductors mentioned from the local market, is there any alternate name for it or something like that coz most of the shopkeepers don't tend to understand what it is and me also don't know much as i'm just a hobbyist.


    Thanks,
    Waseem
     
  2. Pommie

    Pommie Well-Known Member Most Helpful Member

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  3. HarveyH42

    HarveyH42 Banned

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    http://leadacidbatterydesulfation.yuku.com/directory

    A whole forum dedicated to the subject, also kits, and assembled units based on the circuit in your PDF.

    http://www.vdcelectronics.com/batteryminder_12117.htm

    I bought this one for $49 a couple months ago from Northern Tools. Seems to work, recovered two 6 volt SLA, and one small 12 volt. Been trying to get it to do some 12 volt 15 Ah, but only got one up to 9 volts, the othe two won't hold a charge at all. They state that you need 11 volts to get it to start the process, I just put a good battery in parallel. Guess if you catch the battery just as it starts going bad, you might save it. If it's been sitting around for years, probably not...
     
  4. dave

    Dave New Member

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  5. Boncuk

    Boncuk New Member

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    Battery desulfator

    The cheapest and easiest desulfator is you.

    Connect the battery under charge reversely for a very short moment from time to time (max 5% of the entire charging period), one reverse connection not longer than 250ms.

    WARNING: Using a DMM in 10A range it will fry immediately because of the high inverted current flow of 100A+ the moment the charger is reversed. (Generally only the 200mA range is fused.)

    That's the same brute force desulfator circuits apply.

    Boncuk
     
  6. kchriste

    kchriste New Member Forum Supporter

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    Don't forget to wear your safety goggles! :eek:
     
  7. Boncuk

    Boncuk New Member

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    ... and a chain vest.
     
  8. Hero999

    Hero999 Banned

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    Only cheap DVMs aren't fused on the 10A range, most are fitted with a 10A to 13A fast blow fuse.
     
  9. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi Hans,

    I must be missing a point here.

    IIUC, the way you describe it: I reverse the charger leads to the battery.?

    If I use a current meter, it will fry.
    If I dont use a current meter, then where does the 100+ A current flow, surely not back thru the charger.?

    To force reverse charge the battery, dont I need to apply at least a negative voltage greater than the battery potential.?
     
  10. Pommie

    Pommie Well-Known Member Most Helpful Member

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    Hi eric,

    As I understand it "reverse charging" would be the opposite of charging and that is normally called discharging. :confused:

    Mike.
     
  11. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi Mike,
    I would think the same.:)

    To 'force reverse charge' I would expect a reverse voltage to be applied that would be greater than the battery voltage.

    Just swopping the charging leads would take out the rectifiers in the charger.?
     
  12. jpanhalt

    jpanhalt Well-Known Member Most Helpful Member

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    Another thread pointed out that lead-acid batteries are symmetrical when uncharged and can be charged with either polarity. However, I am with those who suggest safety glasses and a chain vest for reverse charging a battery that has become sulfated. You might add a rubber suit too. We had a commercial boat years ago and some worker connected a battery in reverse polarity to an existing battery. It almost killed him.

    $100 for a new battery is cheaper than the risk of reverse charging on the chance the battery might be returned to service.

    John
     
  13. Boncuk

    Boncuk New Member

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    Battery desulfator

    Hi John, hi Eric,

    the idea of reverse charging (which is indeed connecting the charging device the other way round (+ to - and - to +)) isn't new at all.

    Reverse pulsing is also used to manufacture double sided PCBs. Applying steady DC vias and through holes normally become considerably small on both sides of the PCB. Applying reverse pulsing the vias become as smooth as the plain surfaces.

    Having this in mind I made an experiment with a very tired motorbyce battery. I could observe what happened inside the battery because its container was made of transparent material. One electrode in a battery turns into pure lead with a ligh grey surface. Both electrodes were almost black when I first charged the battery.

    Charging of that 6.5Ah battery was terminated manually at 7.2V battery voltage. After five hours the battery voltage was again down to 4.5V. So I tried the above described method. The analog Ammeter of the 25A max charger clicks very loud when polarity is changed reaching the end of the scale, so I assume the reverse current is somewhere in the 100A range.

    Anyway, after 6 full charge and discharge cycles the battery is almost like new. 24 hours after a charge cycle the battery voltage is stable at 6.5V.

    I'm a very cautious person, and that's the reason why I don't use protective clothing or goggles.

    Attachment: PCB with and without reverse pulsing.

    Regards

    Hans
     

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  14. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi Hans,
    I appreciate that reverse charging a 'low discharged battery' is old technology.

    Its the way your earlier post reads that concerns me.

    It appears to say " while charging a battery, its OK to occasionaly reverse connect the charger to the battery for 250mS during the charge cycle"

    If you reversed connected a charged battery to a charger it would either blow the dc fuse or the rectifiers.

    Its a procedure I would NOT recommend to any novice.

    I dont see the connection between battery charging and copper deposition in pcb production.
     
  15. Boncuk

    Boncuk New Member

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    Hello Eric,

    I guess you'll agree that both of them are electrogalvanic or electrolytic processes.

    Hans
     
  16. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi Hans,
    I agree the electro technology is the same.:)

    My concern is a Newbie is going to try this desulphate idea and finish up blinded and/or disfigured if the battery explodes.

    The problem is, which I am sure you are aware, a current of 100A could easily weld the 'temporary' contact in place so that it couldn't be disconnected before the battery blew.:eek:

    BTW, I have seen the 'weld' take place, when a guy used a pair of car jump leads the wrong way around.
    He couldnt get them off and the jumps leads melted.!
     
    Last edited: Aug 24, 2008
  17. Sceadwian

    Sceadwian Banned

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    Is it just me or does it seem kind of silly to try to come up with a completely electrical method to desulfinate batteries? Aren't there chemical methods to desulfinate lead acid cells?
     
  18. Boncuk

    Boncuk New Member

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    I only know of mechanical methods to do that - completely remove the affected electrodes and replace by new ones.

    I watched this at a Turkish battery shop where they also make customer specified batteries. Got my glow plug battery (model engines) made there: 2V/75Ah - lasted one year without charging. :D

    In the "modern" world batteries are "ex & hopp" items.

    Hans
     
  19. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    There used to be a chemical on sale for adding to the battery acid, I suspect it was another scam.
    I havn't seen it advertised for some time, perhaps others have.
     
  20. mvs sarma

    mvs sarma Well-Known Member

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    The best way to take out a battery from sulphation is to add distilled water and charge it at 1/20th of the original rating and for longer time, say 2 days.
    as the recovery starts and cells get warmer, better reduce the current still to 1/30 or so. We were able to recover cells in this process.

    But , one check is needed whether lot of SHEDDING had already taken place, and if so the positive plates may not sustain.
     
  21. Sceadwian

    Sceadwian Banned

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    Hence I ask, what physical material difference is there in a truly new battery vs an old one, over time the back and forth electrolytic response does result in buildup of material, mainly from impurities in added water. I have NEVER seen true distilled water used in the recharging of a large lead-acid cell. The best I've seen is a refill from a long term water bottle sitting idle, which becomes slightly acidic over time from atmospheric carbon.
     

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