Sulfation Remedies Demystified
There are more than $60 billion worth of automobile batteries in use in the world today. The lead-acid battery has been an item of commerce for 130 years. Desulfation has been around for most of this time. The developed world operates between 500 and 800 motor vehicles per 1000 population - in other words, there is nearly one lead-acid battery per person. Battery problems are claimed in desulfation advertisements to be the number-one cause of automobile breakdowns and 85% of battery failures are claimed to be caused by sulfation. Therefore, if sulfation can be reliably treated, there would be a desulfation treatment service center on the main street of every auto parts-and-service retail area in every city. Where are they?
The traditional explanation of sulfation is that battery plates become covered with a hard layer of lead sulfate that prevents the battery from delivering power. Removing this hard layer, it is claimed, restores the battery's ability to deliver power. There is an underlying problem with this theory that traditionalists seem to have been overlooking.
We reasoned that if we wanted to understand desulfation, we needed to run proper tests, start from the beginning, keep an eye on what happens. We kept sets of automotive lead-acid battery positive plates and negative plates from four different manufacturers loosely packed in a covered polyethylene plastic bucket of 1.285 SG sulfuric battery acid for five years. They were arranged to stand vertically and were free to move. The plates had all previously been formed and cycled between three and five times. There were two sizes, when new measured: Small - 9 A-h; Large - 15 A-h.
After five years, some plates were buckled, some were not. The plates made with expanded diamond mesh grids were the least buckled. All the plates made with cast grids were severely buckled away from the pasted side. The active material is more compressed on the pasted side. The thicker the over-pasting, the more buckled the plates. The active material inside the plates had expanded, causing the plates to buckle.
Sulfation in the positives is reversible by charging. Sulfation in the negatives tends to persist and can be difficult to impossible to reverse. Testing should therefore focus on the negative plates. Our researchers built test cells in glass jars using newly formed positives and proven sulfated negatives, buckled as well as unbuckled, from the bucket. Our researchers had a 100% unobstructed view of the battery plates from the beginning to the end of every experiment. (We believe running investigative tests on full sized batteries in opaque containers is like wearing a blindfold and earmuffs to the movies.)
A first test cell was built and put on charge. Within minutes its voltage climbed beyond gassing potential and kept climbing. The potential finally settled at 2.95V at 130mA. The cell was left on charge for two days, then discharge tested. The sulfated negative plate delivered less than 10% of its original capacity. The test was repeated twice. The capacity did not rise. A few grams of cadmium sulfate was then introduced into the electrolyte and stirred. About an hour later, the cell began to slowly draw more current, its voltage fell. It was now accepting charge. The cell was cycled three more times. By the last cycle, the capacity of the negative had risen to 20% of its original capacity. Additional cycling over a period of several days did not improve this figure.
A total of three negative plates were tested with cadmium sulfate. The amounts of cadmium sulfate were varied. It was immediately apparent that very little should be used to avoid severe dendrite growth of cadmium on the negatives. All three negative plates provided essentially the same 20% Ah results.
A fourth and fifth test cell were built and put on a preliminary charge. Again, the voltage of each climbed to 2.95V. The cells were then connected in series to an industrial pulse charger and charged with 10%-on, 90%-off pulsing, at an average of 2.7A. An oscilloscope showed the peak voltage directly across each cell was 3.2V. After 8 hours the peak cell voltages had dropped to 3.05V. Thereafter the cell capacity tested at 10%. Two repeat charge-discharge cycles failed to raise this figure.
Our researchers were able to visually monitor the changes by the color of the negative plates. It was clear there was only partial recovery. The color of the bulk of sulfate crystals inside the plates is charcoal, not white. The conversion to lead metal crystals in the negative plates was evident by the appearance of matte metallic patches. A significant amount of the lead sulfate in the plates, however, remained unchanged. Please note: The lead sulfate inside the plates are crystals and appear nearly black because they do not reflect light. The lead sulfate precipitate that builds up around the plates is amorphous and white and reflects light. There are many different types of lead and basic lead sulfates. People attach far too much importance to the white precipitate. The real problem is deep inside the plates, not on their surfaces!
A best-fit explanation for all of this is most likely to be as follows. Sulfation of the positive plates is easily reversible. Sulfation of the negative plates is not. Lead-acid battery negative plates are made with a paste that is comparable, physically, to cement mortar. The paste consists of finely ground lead oxides mixed with dilute sulfuric acid. This is half pressed, half rubbed into the grids on a conveyor belt in a process called pasting and the plates are then cured. Cured plates are very porous at a microscopic level. The negative plates then undergo a process called formation - prolonged charging - to turn the hardened paste into lead metal crystals.
Then, when a battery is discharged, the lead crystals nearest the outside of the porous material are turned into lead sulfate crystals. The deeply underlying lead, amounting to roughly half of the total, is not changed. It provides millions of tenuous interconnected electrical conduction paths that are needed for the battery to work. Recharging the battery converts all the lead sulfate crystals on the surface back into lead metal crystals. This process can be repeated many times.
However, if a battery is for any reason not fully recharged, the deeply underlying lead conductive paths themselves start to become sulfated. Lead sulfate is not a good conductor of electricity. This leaves the lead crystals on the outside in a precarious situation. The electrical conduction needed to charge the lead crystals nearest the outside is no longer sufficient and the lead crystals are turned into lead sulfate crystals more or less permanently. The underlying lead sulfate takes up more space than lead. The plates buckle. This seems to be by far the simplest, the most likely correct explanation that traditionalists seem to have overlooked.
This is not a theory. Battery manufacturers have begun including high purity conductive graphite in the negative active material of their batteries. They have found that this type of carbon helps to maintain the essential active material conductivity that helps to control sulfation.
When cadmium sulfate is put into a sulfated battery, it goes to work on the underlying sulfated areas that are meant to provide conduction, slowly improving their conductivity, which in turn reactivates the surface crystals. Cadmium sulfate offers the advantage of providing an enhanced visual picture of what is happening. The makers of desulfation remedies and pulsing equipment insist, however, it is the enlargement of the sulfate crystals and the sulfate deposits that cover the plates with an impermeable insulating layer, that are the cause of the problems. They look bad, therefore, they are saying they must be bad. We are convinced these are opinions, oversimplifications and incorrect.
Cadmium sulfate can be seen to electroplate out as spindly, conductive cadmium metal dendrites from the metal of the negative grids when the cell voltage is driven well above its gassing potential. Cadmium on the negatives has the effect of temporarily increasing the electrochemical potential of a lead negative plate from -0.1262V to the electrochemical potential of cadmium at -0.4030V. The effect is to artificially raise the fully charged open circuit voltage of a 12 volt auto battery from about 12.75V to over 14.2V - but the benefit lasts only for a few hours, (cadmium easily redissolves). The electroplated cadmium overflows slightly into the underlying sulfated active material, making it sufficiently conductive to be converted into lead crystals. Repeated overcharging up to 16V and partial discharging causes conduction due to the cadmium to migrate into the sulfated active material, which helps to progressively convert it into conductive lead metal crystals. Cadmium sulfate treatment takes at least three weeks.
Pulsing provides a high voltage that can assist in overcoming the poor conductivity of the underlying material, in much the same way, helping to convert some of the lead sulfate back into lead metal crystals. Battery engineers explain that it takes more energy to desulfate a battery than it takes to simply charge a battery. That is why pulse units that are claimed to use power from the battery itself are far more likely to be doing something else altogether inside the battery. Fully sulfated batteries are impossible to desulfate by pulsing alone. Batteries that are only mildly sulfated respond well to pulsing.
We tried aluminum sulfate, magnesium sulfate, sodium sulfate and zinc sulfate. They appeared to do no harm, provided no benefit - charging with or without was equally effective. EDTA damages the battery.
A combination of pulse charging and cadmium sulfate treatment is commonly used by commercial lead-acid battery reconditioning specialists. Their "feedstock" consists of worn out and neglected batteries. It takes a week and is known to provide a 30% recovery rate on reclaimed scrap batteries. Reclaimed batteries are known statistically to include about 10% undamaged, functioning batteries. Reconditioned auto batteries usually sell between $29.95 and $39.95, on a trade-in basis.
Sulfation is a problem but it is a minor problem, affecting mainly automobile-type batteries. It has long been promoted as a universal lead-acid problem by venturers who seek to profit from selling desulfation products. This attracts many newcomers, who scramble to get into what they believe to be a very easy line of business - only to find it is next to impossible to make money.
If Tom wants to sell a desulfation kit and Dick is willing to pay the asking price, that's free enterprise at work and no one has any right to stand in the way of the transaction. If Harry believes that desulfation kits do not work and says so without naming sellers and buyers, that's freedom of expression.
- The battery community's understanding of how lead-acid works comes from long experience, scientific investigation, extensive testing, hard data and facts -
- but what the battery community knows about lead-acid when it is put to work by the user is based on recollections, interpretations, opinions, anecdotes and beliefs.
If, as is claimed, desulfation removes a layer of white sulfate that forms over the battery plates, why haven't the makers of desulfation products provided proper evidence that is easily understood and that can be believed - a one-shot, continuous time lapse movie showing a fully sulfated battery in a transparent case undergoing desulfation and showing restoration of capacity?
The problem with studies run by universities on behalf of corporations is that they can tailor their evaluation protocols to provide information in a way that can support or dispute claims made about commercial products. Beware of customer testimonials. Try looking at the situation from the testimonial writer's perspective. The writer appears to be accepting responsibility for latent defects in a manufacturer's product. Who would take this kind of risk?
Sulfation is a term that came into use during the early days of the lead-acid battery. The meaning of the word has expanded to imply authority to include and justify every conceivable reason for the eventual performance deterioration and failure of lead-acid batteries. However..........
- Lead-acid batteries that receive the best possible care, are brought to full state-of-charge regularly, consistently last the longest --- eventually wear out as result of the effects of positive grid corrosion.
- Lead-acid batteries that, for a large variety of different reasons, are consistently undercharged, are not brought to full state-of-charge regularly --- fail prematurely as result of the effects of sulfation.
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In the early 1980s there were 6.5 million doctors in the world - all convinced that stomach ulcers were caused by stress. Two unknown doctors, Barry Marshall and Robin Warren from Perth, Australia discovered that stomach ulcers were caused by a bacterium called Helicobacter pylori. No more major operations and no more lifelong disability. A course of antibiotics would cure the problem. Simple. They were ignored by the medical profession for 10 years. Eventually it was accepted they were right and that 6.5 million doctors had been wrong all along. The two received the Nobel Prize in medicine in 2005 for their discovery.
This was not the first time all the doctors in the world have been wrong and there was one who argued against a common misconception and was right. It took ages and untold unnecessary deaths before doctors would accept that germs cause disease. It sounds crazy today but it is perfectly true. The moral of this story is that if someone tells you that a long-held belief is wrong and explains in great detail why it is wrong - yet you ignore the advice because you want to believe that it is the majority that is always right, you are making the same mistake.
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