Lead acid desulfator circuit

This is the place for any magazine-related discussions that don't fit in any of the column discussion boards below.
User avatar
MrAl
Posts: 3862
Joined: Fri Jan 11, 2002 1:01 am
Location: NewJersey
Contact:

Re: Lead acid desulfator circuit

Post by MrAl »

Hi again,


The energy going into the battery is quite small, so i doubt you will have a problem with that.
Of course some ventilation while running is always a good idea anyway.

From the waveform i can tell that since last night the internal resistance has dropped again,
which is a good sign. Whether or not it drops enough to make a difference remains to be
seen through some more extensive testing.
LEDs vs Bulbs, LEDs are winning.
User avatar
MrAl
Posts: 3862
Joined: Fri Jan 11, 2002 1:01 am
Location: NewJersey
Contact:

Re: Lead acid desulfator circuit

Post by MrAl »

Hello again,


Little update...


I had increased the pulse width to 14us and the frequency to 500Hz in an attempt to get
the process moving faster. The circuit still does the same thing more or less, just faster,
but because of the larger duty cycle now the battery also charges as well as 'desulfates'
(if i can call it that yet). This causes a problem because once the battery gets up to
a high enough voltage the circuit has to be disconnected or risk overcharging the battery.
Because of this i think i will go back to 10 or 11us and reduce the frequency again to
200Hz and try that. If that doesnt work, i'll have to go back to 100Hz.

What i am going to do first however is try the cell out now that it is both desulfated
(supposedly) and charged. I am going to connect it to a load i normally use with this
battery and see how long it runs before dipping below 5.90v or something like that.

Interesting, already i seem to see some positive results in that after i took this battery
off of the 'desulfator' circuit and connected it up to its usual load, the voltage stayed
above 6.2v, which is much better than before when it would drop almost immediately
to below 6v. This seems to indicate that the desulfation process works, at least to
some degree more or less. I wont get my hopes up just yet however, i'll wait until
i do some timed load tests and see what happens.

For the 'record', 10us and 100Hz looks like it works ok, and 14us and 500Hz seems
like it charges the battery too much as the process goes on so it is probably not
a good idea to go that high with the duty cycle. If the duty cycle is kept very
low the desulfation process can continue for a longer time before the battery
becomes charged. Would it help to discharge and then use the higher duty cycle
again? I dont know yet. I suspect that the time frame would end up being the
same so it would not serve a useful purpose to do that.
LEDs vs Bulbs, LEDs are winning.
User avatar
Bob Scott
Posts: 1192
Joined: Wed Nov 20, 2002 1:01 am
Location: Vancouver, BC
Contact:

Re: Lead acid desulfator circuit

Post by Bob Scott »

MrAl,

Do you think it might be helpful to separate the charge and desuphation processes? You could insert a capacitor in between the circuit and the battery so that the oscillations only provide AC to the battery, and have a separately controlled current to supply the DC charging current.

From the articles I've read, the authors talk about a battery's "resonant frequency". And I've seen different figures like 40KHz and 1 MHz. Are these real, or might these "resonances" be caused by stray reactances in the authors' circuitry?
-=VA7KOR=- My solar system includes Pluto.
User avatar
MrAl
Posts: 3862
Joined: Fri Jan 11, 2002 1:01 am
Location: NewJersey
Contact:

Re: Lead acid desulfator circuit

Post by MrAl »

Hi Bob,


The cap coupling idea sounds interesting, i'll have to give that some thought.
In the mean time, i set the pulse width back to 10us and freq to 200Hz and
now it isnt charging. Apparently before i had an average of 70ma flowing
into the battery so it was charging.

I would not doubt it if the 'resonances' were due to stray reactances as it
is hard to believe that the mass of the lead plates could vibrate that fast.
I did however hear a tone coming from the battery when i was trying 500Hz.
It's hard to say what was causing this tone however. It's very faint.
If anything, it was vibrating at 500Hz no where near the frequencies quoted
on the web in some places.
I thought about making the frequency variable but im not sure if i will look
into that or not yet.

The battery i was working with tested to be only around 1/4 of its brand new
capacity. I dont know if leaving it connected to the circuit will help anymore
or not.

Also, we really are still hurting for the correct theory behind all of this, if
there is any. We dont know what really works and what doesnt due to the
many different sources that all seem to be quoting a different idea and even
a different circuit concept. One site even says that simply raising the voltage
above 2.4v per cell for some hours will desulfate it, so who knows.

The only thing i can think of at this point is to cut the side of the battery off
and replace it with a clear plexiglass panel so i can see inside to try to determine
if the cells really are sulfated or not, and if so, if 'desulfating' really breaks down
the crystals or not.
I also have to wonder if pulse charging would do the same thing, with the pulses
being able to reach through the crystals.
LEDs vs Bulbs, LEDs are winning.
Robert Reed
Posts: 2277
Joined: Wed Nov 24, 2004 1:01 am
Location: ASHTABULA,OHIO
Contact:

Re: Lead acid desulfator circuit

Post by Robert Reed »

"I would not doubt it if the 'resonances' were due to stray reactances as it
is hard to believe that the mass of the lead plates could vibrate that fast"

I have to agree with that. Lead plates suspended in an electrolyte, boy I envision about a 20 Hz mechanical resonance at best. Or could it be something other than that such as an electrical phenomina that cause the plates to abruptly bend or repel somehow to produce a shaking effect?
User avatar
kheston
Posts: 354
Joined: Wed Dec 03, 2003 1:01 am
Location: CA
Contact:

Re: Lead acid desulfator circuit

Post by kheston »

Some food for thought.

This one seems to infer that it's not rapid fire but instead is more of a shock-treatment methodology that gets the job done:

http://www.diy-electronic-projects.com/ ... -batteries
Kurt - SF Bay
Bigglez
Posts: 1282
Joined: Mon Oct 15, 2007 7:39 pm
Contact:

Re: Lead acid desulfator circuit

Post by Bigglez »

kheston wrote: This one seems to infer that it's not rapid fire but instead is more of a shock-treatment methodology that gets the job done
There are at least three prevailing theories:

(1) Resonance of the mechanical structure. Pulses 'kick'
the cells, and the rest period between pulses sets the
resonance frequency. Pulses dislodge detris bylithotripsy.

(2) High frequency ringing (in the one ot ten megahertz
range), triggered by the rapid transient of the
pulser, which causes the electrolyte liquid to resonant.

(3) Pulse charging with 100 to 5,000 times the average
charge current, for periods of 500 nanoseconds to fifty
milliseconds. As described in US patent 3,963,976

These methods refer to liquid electrolyte lead acid cells.
User avatar
dacflyer
Posts: 4748
Joined: Fri Feb 08, 2002 1:01 am
Location: USA / North Carolina / Fayetteville
Contact:

Re: Lead acid desulfator circuit

Post by dacflyer »

interesting, i never heard of sealed FLA batteries. i have seen some that are non-serviceable like car batteries, but they do have some sort of venting i am sure... or ??
Robert Reed
Posts: 2277
Joined: Wed Nov 24, 2004 1:01 am
Location: ASHTABULA,OHIO
Contact:

Re: Lead acid desulfator circuit

Post by Robert Reed »

Hmmm
Its almost beginning to sound like ultrasonic cleaning in which the electrolyte would be the tank fluid and the plates are the object to be cleaned. Wonder if it would be possible to immerse an ultrasonic transducer directly into the electrolyte?
User avatar
MrAl
Posts: 3862
Joined: Fri Jan 11, 2002 1:01 am
Location: NewJersey
Contact:

Re: Lead acid desulfator circuit

Post by MrAl »

Hi Robert,

Well ok then we have another theory now to add to the pile :smile:
LEDs vs Bulbs, LEDs are winning.
User avatar
MicroRem
Posts: 208
Joined: Tue Dec 04, 2001 1:01 am
Location: Vancouver, WA USA
Contact:

Re: Lead acid desulfator circuit

Post by MicroRem »

Hmmm
Its almost beginning to sound like ultrasonic cleaning in which the electrolyte would be the tank fluid and the plates are the object to be cleaned. Wonder if it would be possible to immerse an ultrasonic transducer directly into the electrolyte?

Why not put the transducer in a water batch and partially submerge the battery, that would keep the acid off the transducer and the water should-maybe-oughta transfer the ultarsonic energy to the battery?

best to all


Tom
User avatar
Joseph
Posts: 681
Joined: Mon Dec 10, 2001 1:01 am
Location: USA,World
Contact:

Re: Lead acid desulfator circuit

Post by Joseph »

Hi all,

Keep in mind, I think, anyway, that the sulfation irreversibly consumes the plate lead.
User avatar
MrAl
Posts: 3862
Joined: Fri Jan 11, 2002 1:01 am
Location: NewJersey
Contact:

Re: Lead acid desulfator circuit

Post by MrAl »

MicroRem wrote:Hmmm
Its almost beginning to sound like ultrasonic cleaning in which the electrolyte would be the tank fluid and the plates are the object to be cleaned. Wonder if it would be possible to immerse an ultrasonic transducer directly into the electrolyte?

Why not put the transducer in a water batch and partially submerge the battery, that would keep the acid off the transducer and the water should-maybe-oughta transfer the ultarsonic energy to the battery?

best to all


Tom

Hi again,

I dont know yet what *really* works and what doesnt. We dont know for sure yet that physical motion
is responsible for desulfating or even part of the process of desulfating a battery. It could be purely
electrochemical.
LEDs vs Bulbs, LEDs are winning.
User avatar
kheston
Posts: 354
Joined: Wed Dec 03, 2003 1:01 am
Location: CA
Contact:

Re: Lead acid desulfator circuit

Post by kheston »

How's the waveform looking, any changes? I wonder whether the changes you were seeing in the battery's internal resistance will reflect a profound change in capacity when load testing.

The ~$14 load testers you were talking about sit right next to the ~$50 one I mentioned in an earlier post. For $14 you get a fixed load, $50 gets you a variable (and larger) load. Not sure what I'm going to buy yet.

My low tech way to test will involve a load and a stopwatch, I think. One could then type the values into a spreadsheet and track performance over time. It would be more fun, however, to set up an automated tester with a solenoid contactor and an ADC that auto-populated a spreadsheet (or other datastore).
Kurt - SF Bay
User avatar
MrAl
Posts: 3862
Joined: Fri Jan 11, 2002 1:01 am
Location: NewJersey
Contact:

Re: Lead acid desulfator circuit

Post by MrAl »

kheston wrote:How's the waveform looking, any changes? I wonder whether the changes you were seeing in the battery's internal resistance will reflect a profound change in capacity when load testing.

The ~$14 load testers you were talking about sit right next to the ~$50 one I mentioned in an earlier post. For $14 you get a fixed load, $50 gets you a variable (and larger) load. Not sure what I'm going to buy yet.

My low tech way to test will involve a load and a stopwatch, I think. One could then type the values into a spreadsheet and track performance over time. It would be more fun, however, to set up an automated tester with a solenoid contactor and an ADC that auto-populated a spreadsheet (or other datastore).

The waveform changed a bit by way of its amplitude. The amplitude came down which tells me the internal R
decreased. Any changes after that have been hard to notice, maybe a little less but not much more.
I am wondering how long it would take to get it very very low now.

I didnt mind a fixed load so i went with the cheaper unit. A variable load could be good for other things too i bet.
My main use was for the car battery so i didnt mind much.
I intended to design an automated tester too, which would test the battery every time the car would start,
but i havent gotten around to do that yet as i am doing other things right now.
I'd just like to mention that the best time to test a car battery is when the car is started, because a good load
is applied right then and there, and it's the exact load the battery has to work with. It can be very informative
to measure the characteristics at that time and compare to the same tests later on in the battery's life.

I'll be getting back to the desulfator shortly too, as i decided to built up a small more permanent PC board for
it...right now it's just a plug board and a soldered MOSFET. This new board is also going to be a test for the
Dremel Workstation to see if i can drill around 25 holes without breaking a bit. I think i can do it but on the
other hand it may take too long because it takes a lot of care to drill with that thing, so im not sure yet
how it will go. I hope i dont break one doing this :smile:
LEDs vs Bulbs, LEDs are winning.
Post Reply

Who is online

Users browsing this forum: No registered users and 10 guests