120V DC Lead battery desulfator! Lightbulb and Bridge Rectifier!

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theAnonymous1

theAnonymous1

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Joined 2004
Steerpike, thank you very much for the explanation!

The test resistors were placed after the bridge rectifier.......

mains AC -> capacitor -> rectifier -> resistor

I measured the DC current after the rectifier, not the AC current before it.

My meter is a Fluke 111 and the motor run cap measures 7.45uF with it. AC line voltage is ~119.
 
star882

star882

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Joined 2007
Steerpike said:


Certainly the capacitor wastes no energy. But safety isolation would require a transformer, and if you are putting in a transformer I think you can do better than a simple resistance charger (which is what the capacitor effectively is, as seen by the battery)

Nickel-cadmium and Nickel-metal-hydride like constant current.
Lead-acid batteries like to be charged with constant voltage; constant current charging them over a long time period shortens their life.

Constant voltage can be achieved very efficiently by means of a switched mode power supply - several ICs exist to do this with minimal support components.

An old AT computer power supply should work - with a small modification to set the voltage.
Click to expand...
An AT power supply will not put out enough power for a fast charge. That and modifying it for enough voltage is not something most EV builders would do for the first build, let alone try to build a switcher from scratch. (A typical EV pack ranges from 72v for a compact to over 250v for a large truck, at a few dozen to few hundred Ah.)

Most EV systems are isolated from the chassis to avoid a wire grounding out causing a short circuit. Many cheaper EV chargers are nonisolated switchers as isolation is not required. Just a circuit to verify isolation of the pack from the chassis.

Note that pulse chargers for lead acid batteries are basically current sources that are electronically switched on and off. The idea is to start with a constant current charge until a threshold voltage is reached, at which point the current is modulated as a form of slow PWM. It actually works better than traditional CC/CV charging if implemented correctly.
http://www.duoregen.com/images/PDFs/Ak_Uni_Charging.pdf
 
star882

star882

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Joined 2007
Steerpike said:
Oh, like a toyota prius? Or is that different & classed as a hybrid? They hardly exist here in Africa!
(We still have leaded gasoline)
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Most hybrids, including the Prius, are a form of EV. (Note that some hybrids, such as the hydraulic hybrid and the "Amy Aldrich" gas/water hybrid, are not EVs.)

What I had in mind are homemade EVs, such as this one:
http://jerryrig.com/convert/
 
E

EWorkshop1708

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Joined 2004
MJL21193 said:
Sorry to go back on topic...:)

I tried it with a dead (I mean DEAD :dead: ) sealed 12V, 7AH battery. Left it going overnight and presto! It charges now! Load tested it with an 8 ohm dummy and it seems as good as new.

Thanks EWorkshop1708 :up:
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Sweet!!! Your very Welcome!

Did you use a capacitor, or a light bulb?

It's nice to get some use out of dead batteries.

I see how you folks are trying different methods of the high voltage charging. I'm in the process of designing a new one too, that should be safer from error, and runs cooler.

I'm also considering a plan for making a high-current version, with a powerful transformer. I found you can also desulfate an old 12V car battery if you use 3 car batteries in series (36V, hundreds of amps) to charge it with for about 1 minute, until you hear loud bubbling, then it also takes a charge from the charger again.
 
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EWorkshop1708

Member
Joined 2004
Update on the 120V desulfator charger.....

I built a new one out of different parts, and put it on some batteries.

This new one uses a 4.7uf capacitor on the AC side of the bridge rectifier. I also added a large 4.7ohm wirewound resistor for reverse-battery protection, and a 0.22ohm metal-film resistor on the AC side to act as a fuse under any faults.

I love the new capacitor desulfator. NO wasted heat!!!! No excessive power usage either!

I notice, the capacitor charger has a higher peak current than a lightbulb charger. When you put the clips to the batteries, I get a pop, like a small arc! I guess that's the capacitor charging, and that may help on stubborn batteries. I wonder if the peak pulses from the Capacitor on 60Hz, may desulfate a battery better than a series lightbulb that soaks up most of the energy.

I tried this new desulfator/charger on my lead batteries, but I even fully charged a small Ni-Cd with it. This seems like a rather safe charger, being there's no heat, and it charges with such a low current.

Now this one can be left on for hours and days, without energy waste.
 

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Praudio

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Joined 2002
Few days ago my car don't start; after usual test my battery was culprit .
Voltage was about 12.75v with 2 hours charge and 10.75v 2 days later.
Start test with lightbulb method: battery was at 12.2v(and bulb on ) and 8 hours later it is 10.85v. It's normal or I do something wrong?
Today will built second version with capacitor ,resistors.
This battery is 5 years old and first time in trouble.:confused:
 
Steerpike

Steerpike

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Joined 2006
web.eject.co.za/s8nspawn/hifi/ak/index.htm
Praudio said:
and 8 hours later it is 10.85v. It's normal or I do something wrong? Today will built second version with capacitor ,resistors.
This battery is 5 years old and first time in trouble.:confused:
Click to expand...

The battery could have a single short-circuited cell. If so, no amount of charging will fix it, because no charge voltage can ever appear across the dead cell.
 
Pano

Pano

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Very cool idea, thanks!

Sure wish I had known about this years ago. Have killed more than my fair share of batteries. Also wish I had known about it when I lived in Honolulu. Very hard/expensive to get rid of old batteries there, so they are everywhere on the curbs and vacant lots. Always thought that if only someone could make money by picking them up......
 
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Praudio

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Joined 2002
Just built desulfator second version with capacitor and resistors; use it on an other(not used for 8 months) battery: start at 11.2 v and 2hours later it is 12.25. This time seem to work ! But now what next ::: I wait until voltage reach 15/16 v or ?
 
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star882

star882

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Joined 2007
xplod1236 said:
I have built the light bulb/rectifier version; When I connect it to a lawn mower battery (12v), I get ~112v dc at the battery terminals and no current through the bulb. I have tried this on 2 different batteries (both dead lawn mower batteries), and I get the same result with both. What am I doing wrong?
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Check the liquid levels. Add distilled water up to just above the plates if needed. Then leave the circuit running for a long time.
 
T

tomtriglav

Member
Joined 2009
24 Microfarad capacitor per amp

Hi
This is a great idea. If you want the maximum voltage and at least 1 amp of current flow you can use a 24 microfarad capacitor per amp. If you connect them in parallel you can increase your amperage. Just be careful as you are dealing with live 120volts. Please enclose in a metal box with a fan with a cut out door switch. Sounds like an old microwave to me. You can also use the timing controls on it.
Take care
Tom
I assume no liability for anyone trying to build this product. Build at your own risk. Remember when charging batteries explosive gasses are released! Always wear safety glasses to protect your eyes from sulfuric acid.
 
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