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DIY Cheap battery charger desulfates old lead acid batteries - $12

Discussion in 'Survival (Preps & Homestead)' started by minimus, Mar 31, 2010.



  1. minimus

    minimus Guest

    File this under "Don't try this at home kids" but it works.

    Its a very simple capacitive battery charger from scrap parts but if you have little respect for electricity or batteries its best you go buy a ChinaMart charger ... and more batteries.

    I have restored three batteries to service in the last week with this charger, the first was my ATV battery, took about 4 hours. My regular charger would not wake up a dead cell that refused to take a charge (notice the other cells were bubbling but #3 cell refused). 4 hours later the cell woke up after being stung by 150 volts of buzzing 120 cycle power.

    Second battery was my trolling motor battery, an overnight charge did the trick. Was 9.7 volts all sufated up, looked real bad. The next morning it showed 14.8 volts and all cells bubbling with a hot charge. After taking it off the charge in the morning that afternoon the voltage settled down to 12.8, a good hot battery.

    Third was my lawn tractor battery, took only about 6 hrs.


    Be damn careful, use the charger outside of your garage or shop, always hook up the battery leads BEFORE plugging it in, always unplug the charger BEFORE checking battery leads. This thing can KILL you if you are not careful. Stay away from the battery while charging. Do not charge a battery while wired in the vehicle, unless you want 150 vdc smoking your voltage regulator, alternator and electronics ...

    [​IMG]

    My charger is fused to 5 amps with a neon indicator lamp to show when its hot. Its built in an Army ammo can.

    I use a 50 mfd ac motor run capacitor for a 2 amp current limiter, just enough juice for a slow overnight desulfating charge. I used a 25 amp/400 volt bridge rectifier. This charger will charge any lead acid battery, no matter what the battery voltage is ... 6, 12, 24 volt ... it doesn't matter. My cost to build it was $12.

    The problem with regular voltage limiter chargers is they cannot equalize a battery or desulfate cells. Not enough electrical pressure to bust up the lead sulfate that's insulating the cell plates.

    The power output is limited by capacitor size - 25 mfd per amp output. If you want a 1/2 amp charger use a 12 mfd capacitor, if you want a 6 amp charger use (3) 50 mfd capacitors wired in parallel , ect , ect, ect ...
     
    Last edited by a moderator: Mar 31, 2010
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  2. minimus

    minimus Guest



    This video shows the capacitive charger hooked up, the battery pulls the voltage down while charging, if he unhooked the leads it would show about 150 volts from the charger.
     
    Last edited by a moderator: Dec 26, 2015
  3. johnlvs2run

    johnlvs2run New Member

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  4. minimus

    minimus Guest

    Does that work like one of the aci chargers?



    No, it actually desulfates lead acid batteries, the aci charger is a $3 joke.
     
  5. 7th trump

    7th trump Banned

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    Is the capacitor a polarized capacitor?
     
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  6. jingles

    jingles New Member

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    Thanks for the tip, will have to try this.
     
  7. Fullpower

    Fullpower Seeker Seeker

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    Thank you.
    I will construct a version of this device.
     
  8. Pinguino

    Pinguino New Member

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    Wow I've got to look into this, I've got probubly 2-3 old tractor batteries laying around for just this occasion
     
  9. minimus

    minimus Guest

    Nope, its a motor run capacitor. It can be found in any junkyard air conditioner.
     
  10. johnlvs2run

    johnlvs2run New Member

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    The aci charger has been working great for me for 4 years.

    And it doesn't electrocute me when I use it. What makes you think it's a joke.
     
  11. minimus

    minimus Guest

    It only puts out about 14 volts.

    14 volts charging a dead battery of 10 volts = only 4 volts potential across the sulfated up battery plates.

    The lead sulfate acts like a resistor and eats up the power from the charger acting like a heating element. The battery (and charger) just gets hot, not charged.

    When a good battery takes a charge the voltage rises and the potential difference between the battery and charger decreases (takes less current) and the battery stays cool.

    4 volts is a joke. Its a great battery charger for a good battery but it won't put a bad battery back in service.



    Yes, the capacitive charger can shock the **** out of you if you're not careful, that's why its not on the market.

    Product liability.

    But it charges the hell out of old crappy batteries.




    zap
     
    Last edited by a moderator: Apr 2, 2010
  12. wallew

    wallew Gold Member Gold Chaser

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  13. Pinguino

    Pinguino New Member

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    Wow think I'll go Min's route and buy some Ag with the leftovers!
     
  14. Pinguino

    Pinguino New Member

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    Where do I find a 25 amp/400 volt bridge rectifier? Min you got a picture of your setup?
     
  15. Someone_else

    Someone_else Silver Member Silver Miner

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    Here is one with your desired rating for $3:
    http://www.allelectronics.com/make-a-store/item/FWB-254/25-A-400-PIV-BRIDGE-RECTIFIER/-/1.html
    And here are many others, some with higher current or voltage ratings:
    http://www.allelectronics.com/make-a-store/category/110/Bridge-Rectifiers/1.html

    Here are clips for $2:
    http://www.allelectronics.com/make-...0-AMP-BATTERY-CLIPS-RED-AND-BLACK-PAIR/1.html

    Here is a low value (5uF) motor start capacitor for $1.20
    http://www.allelectronics.com/make-a-store/item/MPC-5/5UF-250V-MOTOR-START/RUN-CAPACITOR/1.html

    Hope this helps.
     
  16. Pinguino

    Pinguino New Member

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    Thanks Someone.
     
  17. minimus

    minimus Guest

    I have modified my desulfator and reduced the run capacitor to 25 mfd to decrease amp output to 1 amp and increase charge time.

    It seems a longer charge time allows the desulfator to do a better job.
     
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  18. Jimfrancisco

    Jimfrancisco Seeker Seeker

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    Unless you have a battery that can be stripped down and the plates scraped, there is no way to "desulphate" a dead battery. It is simple physics and a little chemistry. You might knock a little more life into a soft battery, but you are not desulfating anything.
     
  19. minimus

    minimus Guest

    More links to high frequency high voltage desulfators ...

    http://home.comcast.net/~ddenhardt201263/desulfator/desulf.htm

    Research Forum

    http://leadacidbatterydesulfation.yuku.com/

    Some general hints for desulfating various sorts of lead-acid batteries

    The following will help to get the most out of desulfation efforts:

    * The chemistry of desulfation processes speeds up at higher temperatures. If possible, heat the batteries to 40-50 degrees C for best results.
    * If batteries are heavily sulfated, an initial treatment with EDTA is recommended, followed by pulsing.
    * Although gel cell batteries are apparently sealed, they still dry out with time, and must be refilled to bring them back to life. In order to rehydrate them, they must be carefully opened and distilled water dripped into the vent holes. This procedure will vary depending on battery type. On the batteries I tried (made by CSB), it took about a minute to pry off the plastic lid over the vent holes, and remove the caps. It won't take much to rehydrate the gel material, in any case standing water in the cell will eventually go away. Note Oct 2003: The consensus of opinion from the BBS postings is that these types of batteries are just not generally recoverable, and are not much helped by pulsing, especially if they are at all old.
    * Several cycles of pulsing, charging and discharging are needed to show results. It is recommended to try long periods of trickle charging with the desulfator, and shorter discharge periods to determine progress.
    * It is often the case that one cell is worse than the others. If there is a shorted cell, there is often no way to recover the battery, and charging attempts will usually just heat up the good cells.
    * The fast rise time pulses that the circuits in this web site produce require that short, fairly heavy wire or shielded cable be used to connect to the battery terminals.
    * Multiple batteries can be desulfated in parallel, but the progress will be slower. Results can be seen in some cases in a week, but might take as long as a month for full recovery.
    * Excessive pulse amplitude for a given battery size can cause "shedding", or the driving off of active plate material in relatively large pieces, something to avoid. This is not likely a problem unless a small gel cell battery is used with a large pulser.
    * Connecting other equipment across the battery to be desulfated is not necessarily a problem, but in some cases the loads might shunt away some of the pulser's output. While most unfiltered battery chargers present a high impedance to the current pulses, such things as inverters might not. In such a case, place a choke in series with one of the inverter leads to eliminate the problem. This can be a simple ferrite toroid with one or two turns wrapped around it.

    This page will be updated as more results come in. Let me know, and I can place your data here.
     
  20. Jimfrancisco

    Jimfrancisco Seeker Seeker

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    Any kind of desulfating that could be done inside the battery case means the sulphate falls to the bottom of the case - and with today's batteries being made ever more compact, it wouldn't take long for the lead sulphate to reach the plates, and kill the battery completely.
    Just use your batteries sensibly, keep them on a float charge and topped up with water, and they can last 12-15 years easily (for a quality battery).
    I've been maintaining fire pump batteries (designed to start a big Lamborghini straight six diesel) for years, and if they are looked after properly then they will last that length of time.
    Treating them badly, as in draining them and then recharging, will shorten their lifetime to a year or less depending on the battery. Messing with trying to desulphate batteries is like keeping a brain-dead person alive.
     
  21. wallew

    wallew Gold Member Gold Chaser

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    No offense to anyone. But this is the exact battery charger a buddy of mine uses in his company shop. He works for a transportation company and he has to maintain a fairly large fleet. He's worked there for more than ten years and he can't remember them ever having any other charger. And they abuse it to pieces. Yet it just keeps on working.

    ME? I have military vehicles that are set up for 24v starter. And it's diesel and no electronics. So having the ability to turn over that starter 'heartily' as it were is paramount. And I can't talk about desulfating batteries per se. But I have cooked my fair share with that particular charger in the past few years. Never hurt them and they always have come back to life. But I basically use the Interstate battery the military uses.

    I expect that this charger will probably be the last one I purchase. I don't use it often, but when I need it, it works RIGHT NOW.

    If you break down the cost over say twenty years, it's less than $15 a year. About $1.50 a month. Pretty cheap insurance if you ask me. And yeah, twenty years is how long my last Schumacher lasted. And it wasn't NEARLY as nice as this one is.
     
  22. minimus

    minimus Guest

    Using Epsom Salts to rejuvenate old batteries.


     
    Last edited by a moderator: Dec 26, 2015
  23. Professur

    Professur Gold Member Gold Chaser

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    I'm just going to throw the old warnings here. Charging batteries produces hydrogen. Also, if your dead battery was left out in the cold and froze, it may have swelled and caused damage to the plastic case. If there's any sign of deformity to the case ...DO NOT TRY TO CHARGE IT. I don't care how great a charge you have ... it will not end well.
     
  24. wallew

    wallew Gold Member Gold Chaser

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    ah, grasshopper, for those lesser mortals your warnings are true. for those of us who run military vehicles? the only part of that which is still valid is the 'charging produces nitrogen' - SO YOU BEST DO IT OUTSIDE.

    As we only have a car port, no problema.

    But I HAVE COOKED batteries that have set out in the vehicle during deadly cold winters. HELL, I've been camping ABOVE 9500 ft, IN OVER TWO FEET OF SNOW, IN FEBRUARY and the high for the day was right at 10 degrees. But the sun was out and it felt great. Plus the deuce was always warm and toasty on the inside. As long as you have the rear cover on with both curtains (front and rear) in place, it would warm up well above freezing just by running the dual mantle Coleman lantern I always have with me (2 of them actually). So much so that the two guys that I was with and I had to remove our jackets because we were getting too warm. AND GOD BLESS THE ARMY, with the rear covered, you literally could see NO LIGHT being emitted from the truck at all.

    While the military doesn't believe in creature comforts, they do DEMAND that their stuff hold up to weather and abuse MOST VEHICLES COULD NOT SURVIVE. SO you need a tough charger to handle it.

    For those of you who do NOT run military vehicles, be my guest. Build your own charger. It just won't hold up to MY NEEDS. That's why I finally replaced my old Schumacher with the new S-3000. This baby has everything I need and then some. I can and have jump started a deuce with this particular charger. Turned the big multifuel engine over in a heart beat. It started right up and then the charger in the truck took over the job of managing the electricity.
     
  25. Professur

    Professur Gold Member Gold Chaser

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    If you've a battery that produces nitrogen, feel free to ignore my warnings.
     
  26. GoldWampum

    GoldWampum Midas Member Midas Member

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    Pretty darned slick Minimus, Sort of a super equalizer. Useful information.
     
  27. Jimfrancisco

    Jimfrancisco Seeker Seeker

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    The specs on that charger/booster are nearly identical to mine, and I have a LOT of batteries. Between cars, generators, lights, solar panels and electric fences, it's easy to lose track of what needs charged and when. It is nice just to be able to clamp on the leads to a dead car and have it start like you just put a new battery in it!
    As I said though, any sulphate that falls to the bottom of your battery will end up shorting out the plates - and all of a sudden, rather than having a low 12v battery, you end up having a very low 10v battery, which is no use to anyone. By all means boot them up with as many amps as they need to get them started, but trying to desulphate a LA battery is just asking for trouble. At least with a proper charger you can tell when your battery is going soft, rather than having a sudden short in one cell and a useless battery in the middle of nowhere!
     

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