120V DC Lead battery desulfator! Lightbulb and Bridge Rectifier! - diyAudio
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Old 1st May 2009, 05:57 PM   #1
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Default 120V DC Lead battery desulfator! Lightbulb and Bridge Rectifier!

Hello folks. The lightbulb trick for testing amps is great, and familiar around here, but there's also other uses for them, along with a few additional parts....

(See schematic photo for details)

I wanted to share some valuable information with you savvy folks.

Don't throw away your old 12V car batteries!

When a battery is bad, it's because it won't take a charge anymore (AKA battery no longer conducts electricity) so the battery never gets charged. That's because a dead battery has insulating sulfated lead plates - from sitting around dead for too long. or never getting a complete charge.

However, that only applies to a regular 12V charger! A bad battery may only conduct a few mA, or none at all from a typical charger, so the battery voltage rises to 15V+, and the charger falsely detects a full charge, and never charges the battery.

Now if you force 10X the nominal voltage, and give the battery over 120 Volts DC, despite the sulfation, the battery WILL conduct electricity, and start taking a charge.

The bulb will glow when it conducts electricity, and starts flowing current, which makes a great indicator.

Once the battery starts conducting, the voltage will be about 25V for a split second, then drop to below 12V gradually, then start rising again as it charges!

Being the 120V desulfator is really low current, once the battery has been treated, you can put a regular charger on it, and monitor the battery voltage, and check for gassing. Or the best way, if you have the time to kill, is to leave the 120V desulfator on the battery for several days or even weeks depending on battery condition, for the best complete treatment.

Once the battery starts taking a charge again, it has to be left on a slow charge for a long time, then cycled just a few times to bring the battery to good condition.

The constant, unfiltered, nasty pulses from the rectified DC help to break up the sulfur, so the longer the treatment, the better.

A typical 60W bulb will use less than 500mA, and a smaller 25W bulb will use less than 250mA, so you can use a lower power bulb to save electricity for very long treatments, but for quicker results, the more watts, the better. These low currents pose no danger of overcharge or overheating for typical large batteries.
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Old 1st May 2009, 06:10 PM   #2
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Also, I've been collecting "dead" batteries from folks that are happy to dispose of them. One guy gave me a battery that would not start his cars, or accept any charge, it turned out, it was very low on water, and very sulfated. After adding water to all cells, and desulfating, it starts MY car very well!

And I've had 100% success with liquid batteries. The really BAD ones, require a few charge/discharge cycles to get them right. As long as the plates are good, and there's acid or water, they are fine. Most, but not all batteries get to 100% capacity after a while, however, it's still VERY useable, and the capacity increases after a few cycles, which helps to futher desulfate the battery. AGM's not as much luck, but it's now been revealed that when the voltage is too low, add more acid.

Check this thread out where I posted the original 120V DC schematic:
http://www.diygokarts.com/vb/showthr...?t=2276&page=2 Several folks are researching ways to extend the life of old batteries.
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Old 1st May 2009, 07:08 PM   #3
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Looks worth a try! BUT noobies ought to be made aware that this sort of circuitry is exceptionally dangerous! A serious electrocution hazard.
 
Old 1st May 2009, 07:29 PM   #4
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Does this really do anything but charge the battery? I mean point of desulfator is to send short pulses to battery that make sulfat or how do you say to resonate, and break it away from cells...

Eva wrote about this some time back, very great and understanding, what is the point and what is going on...
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Old 1st May 2009, 09:16 PM   #5
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Quote:
Originally posted by Steerpike
Looks worth a try! BUT noobies ought to be made aware that this sort of circuitry is exceptionally dangerous! A serious electrocution hazard.
True, very true.

It's obvious it has a potential for danger, which is why I never posted any warning.

I say keep the n00bs on circuits 30V or less, the big boys can play with high voltage. I recommend unplugging the cord whenever connecting, or disconnecting the leads from the battery to avoid shock. (as I have found out, lol)

Also, this circuit mainly charges the battery, but the high voltage forces current through the sulfur on the plates, which breaks it up.

I also have to add, the desulfator works great to start the charging/desulfating process, but works best in an overcharge state or on a full battery, because the very slow bubbling and gassing helps to chemically desulfate the battery.

Being that it's unfiltered 120V DC (162V peak) the pulses from the rectified DC do the job of desulfating. The battery voltage drops around 12V only when it starts charging again, and the internal resistance drops. A regular desulfator makes high voltage pulses anyway, just at a much higher frequency, but 60HZ line (120hz rectified) has been working just fine for me.

Also the high frequency desulfators don't always bring a battery from a dormant state, but brute-force 120VDC will. Heck, the 120V conducts great, even in plain water, and makes hydrogen bubbles on the clips, so it also will conduct inside a wet battery as well, forcing a charge.

You could try a regular desulfator once a battery is restored with the 120V cord, to even help further desulfate the battery, but in my experience so far, it hasn't been necessary.
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Old 1st May 2009, 09:22 PM   #6
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Quote:
Originally posted by luka
Does this really do anything but charge the battery? I mean point of desulfator is to send short pulses to battery that make sulfat or how do you say to resonate, and break it away from cells...

Eva wrote about this some time back, very great and understanding, what is the point and what is going on...

Luka, The main goal is to make it accept a charge, more than just the desulfation itself. Because a sulfated battery won't charge anyway, but one treated with 120V will.

I also have an unregulated 12V charger, and I find just a few minutes on the 120V DC desulfator cord, will then allow the 12V charger to charge the battery. You just have to charge slow (2A or less) and steady to avoid excess gassing when bringing it back to life. However, it works best if used on the 120V for a few hours or days.

After a few charge/discharge cycles, the battery will gas less, and be very able to take high-amperage charges. One just restored may handle 10A, but after a while of use, I can give 60A charge without too much gassing.
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Old 1st May 2009, 09:28 PM   #7
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seems a bit hard on battry if you ask me. I mean 160Vpk, it is limited, but still...I look on scope, and if it was pretty bad battery, it wouldn't be more then say 30v max... I gues since you have light in series, voltage willl never be higher then id needs to be... I just didn't know [never tested] you could do this with mains..
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Old 1st May 2009, 09:37 PM   #8
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Quote:
Originally posted by luka
seems a bit hard on battery if you ask me. I mean 160Vpk, it is limited, but still...I look on scope, and if it was pretty bad battery, it wouldn't be more then say 30v max... I gues since you have light in series, voltage willl never be higher then id needs to be... I just didn't know [never tested] you could do this with mains..
I didn't know either, or I wouldn't have disposed of 4 bad batteries over a year ago! It was just an experiment to see what would happen, and so far, so good, now I'm collecting as many lead-acid batteries as possible.

You got it. The lightbulb is a convenient series resistor, and if the battery is truly worthless or dry, the bulb won't light at all and you will have 120V at the battery terminals, but it's very rare that happens. The voltage on a workable battery doesn't stay over 20-28V for more than a few seconds at most anyway, before dropping immediately down to below 10-12V, and lighting up the bulb.

It's still only 250-500mA, so it's actually not very hard on the battery. However, charging on a regular charger after a fresh restore is, but IMO it's well worth the risk of possibly damaging a "bad" battery to try to get some use from it.
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Old 1st May 2009, 09:48 PM   #9
luka is offline luka  Slovenia
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If battery if "dead" you can't lose anything, trying doesn't hurt. So I guess if it works for you, it could/will for others too.. good job
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Old 1st May 2009, 09:49 PM   #10
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The battery holds its own terminal voltage pretty constant, and as the mains wave peaks, it just causes higher current to flow - most of the voltage is dropped across the series resistance. It doesn't seem to upset the battery at all.

Rechargeable shavers used to work like this: a 3.6V NiCd battery, charged directly from the mains by nothing more than a series resistance. Now I suspect they use more sophisticated control.

I have only a cheap car battery charger (transformer - rectifier - thermal cutout); even a 'dead' battery always manages to get about 2 to 4 amps from it, but a dead battery never fully charges - even after several days. Hydrometer testing always shows 5 fully charged cells and one flat cell.
 

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