Hi MikeML thanx for your honest reply.But i have seen in come cases even vibrating(very less frequency as conpared to pulse charging) the battery before discharging leads to increased capacity and im talking of newly formed battery that is not subjected to any electrolyte straticification.Is pulse charging really that great??

Pulse charging dates back to the 60s, the Dutch called it electrophoor. Originally for extending the life of zinc/carbon cells, it borrows from an electroplating technique of periodically reversing the current flow to get smooth even plating - just raw DC would plate some of the zinc back on the casing, but it was rough and granular. Putting a resistor in parallel with the half wave rectifier put a small reverse flow between each pulse of raw DC current.

The same method applies to nickel chemistry, especially Ni-Cd. Years ago I experimented with this, but found the results with 50Hz unimprssive. In the end I used a capacitor coupling with a selected combination of fast silicon and Shottky-barrier rectifiers on the transformer output of a surplus SMPSU.

The circuit was the basic capacitor input voltage doubling rectifier, the forward pass rectifier was the basic fast silicon so the Trr produced the required reverse spikes. The clamp rectifier was SB to limit the amplitude of the reverse excursions. The arrangement worked brilliantly with Ni-Cd cells, but the results with Ni-Mh were less impressive.

Most of the so called "intelligent" chargers have a pulse charging mode, that applies to both nickel & lead chemistries - so far I've not bothered taking any measurements.

 

Punkdunk
I used to post under the name of "tucsonshooter" on the lead acid battery desulfator forum and am the designer of the "direct drive" and "voltage doubler" designs. The ringing that people see using a pulse charger is from the inductance of the battery leads, and the battery. I have a good friend that is a PhD chemist here in Tucson who owns his own company. I asked him about the possibility of sulfates having a resonant frequency. The short answer was "NO".

One big problem with pulse chargers/desulfators is that there is a lot of bad information out there. The "resonant frequency" myth really needs to go away.

 

Punkdunk
I used to post under the name of "tucsonshooter" on the lead acid battery desulfator forum and am the designer of the "direct drive" and "voltage doubler" designs. The ringing that people see using a pulse charger is from the inductance of the battery leads, and the battery. I have a good friend that is a PhD chemist here in Tucson who owns his own company. I asked him about the possibility of sulfates having a resonant frequency. The short answer was "NO".

One big problem with pulse chargers/desulfators is that there is a lot of bad information out there. The "resonant frequency" myth really needs to go away.

Thankx for your reply Lestarveled

 

Punkdunk
I used to post under the name of "tucsonshooter" on the lead acid battery desulfator forum and am the designer of the "direct drive" and "voltage doubler" designs. The ringing that people see using a pulse charger is from the inductance of the battery leads, and the battery. I have a good friend that is a PhD chemist here in Tucson who owns his own company. I asked him about the possibility of sulfates having a resonant frequency. The short answer was "NO".

One big problem with pulse chargers/desulfators is that there is a lot of bad information out there. The "resonant frequency" myth really needs to go away.

The "resonant frequency" thing is probably a fairy tale, but AIUI: the pulse chargers for lead-acid, supply current limited pulses at just under 30V to break through the sulphation. In general; if the sulphation is mild enough for that to fix it - all good and well. In the past I've devised chargers that could shift sulphation that "intelligent" chargers couldn't, but the battery by that point was way past recovering a worthwhile % of capacity.

Its not exactly clear why pulsed current limited charging is any better than steady current limited DC, I think the microprocessor samples the terminal voltage between pulses and calculates some conclusion about battery status - besides; "pulse charging" looks good on the adverts.

 

..."pulse charging" looks good on the adverts.

You broke the code...

 

"Pulse charging" is a very poor description because there is very little charging is going on . "Pulse conditioning" is a far better term for what is being done to the battery. Too many people think of a lead acid battery as a big capacitor, in that all you have to do is replace the energy you used plus some extra. They don't realize that a battery has to be charged is a specific way in order to maximize the conversion of sulfates back into sulfuric acid. Failure to charge a battery correctly leads to sulfates building up and hardening on the plates and thus, early battery failure.

Pulsed desulfation, where a battery is pulsed with high amperage pulses (>100 amps) will often bring a battery to a higher state of health. The success rate varies based on battery size and construction, amount and age of sulfation, and power of the desulfator. A battery that has sat in a shed to two years is a waste of time. A $19 motorcycle battery from X-Mart is a waste of time.

There are a huge number of desulfator circuits out there that are grossly under powered, producing less than 5 amps of pulse current. These bogus circuits have done more to sully desulfator usage than to desulfate batteries. It takes a lot of energy to convince sulfates to reform into sulfuric acid.

Go BIG or go home. The little inductive kickback circuits out there are a waste of time.

If you are interested in desulfator designs that actually work, go to the "lead Acid desulfator forum", ( http://leadacidbatterydesulfation.yuku.com/ ) under the "pulse charging and desulfation" section. Look for "Direct drive" and "voltage doubler". There is a mountain of designs, information, personal experience, and success stories there, from around the world.

I have kind of moved on from desulfators and have focused on how not to let a battery sulfate, as in, better battery chargers.

 

"Pulse charging" is a very poor description because there is very little charging is going on . "Pulse conditioning" is a far better term for what is being done to the battery. Too many people think of a lead acid battery as a big capacitor,.

A sulphated battery *IS* a capacitor, the white crystalised sulphate is pretty much an insulator - and not exactly a terrible dielectric. If you just stick DC across the terminals, very little is going to happen.

Most of my pulse charging experiments were with Ni-Cd - which is an entirely different reason for using pulses.

What little of these experiments I extended to lead acid batteries was pretty much a "while I was bored" sort of thing. The results were pretty much a dead loss - in most cases I'd simply hooked up by soldering leads to the lead terminal posts - I've since learned that tin contamination can migrate through a solid bulk of lead and poison the plate at each end of the battery.

Maybe someday I might revive the lead acid experiments, but for now; if the Optimate can't revive it, it gets scrapped.

 

.......A sulphated battery *IS* a capacitor, the white crystalised sulphate is pretty much an insulator - and not exactly a terrible dielectric. If you just stick DC across the terminals, very little is going to happen.........

If you view a lead acid battery in a high speed pulse domain (AC), I agree, it looks like a capacitor. The plates in a battery are the same topology as any capacitor. This is one reason why pulsed desulfation is advantageous, the plates in the battery form a capacitor, and the "capacitive divider" effect forces the same amount of energy to be imposed on each cell regardless of the "state of charge" of each cell. In other words, when you pulse a battery with a fast enough rise time, you are guaranteed to hit each cell with the same amount of energy. In my experience, most batteries fail because one cell is weaker than the rest of the cells in the battery. DC chargers exacerbate this condition because the healthier cells will accept charge and rise to a higher voltage compared to a weaker (troublesome) cell which will remain under charged. Again, in other words, using a dc charger, on a troubled battery, healthier cells will be over charged and weaker cells will be under charged. Pulse desulfation minimizes this undesirable effect.

 

If you view a lead acid battery in a high speed pulse domain (AC), I agree, it looks like a capacitor. The plates in a battery are the same topology as any capacitor. This is one reason why pulsed desulfation is advantageous, the plates in the battery form a capacitor, and the "capacitive divider" effect forces the same amount of energy to be imposed on each cell regardless of the "state of charge" of each cell. In other words, when you pulse a battery with a fast enough rise time, you are guaranteed to hit each cell with the same amount of energy. .

Someone once brought me a sulphated motorcycle battery - it defied all my "brute force and ingnorance" desulphators, so I hooked it up to the AC on the secondary of a half-bridge SMPSU.

The end result held a charge long enough for them to sell the bike anyway.