I found the following two articles on the Net when looking for some concise information to give to my customers and came up with these two articles:
Quoted content from a blog on batteryuniversity.com
Sulfation is an unavoidable effect of battery cycling. Lead-Sulfate crystals are chemically formed by the discharge process as electrons are depleted from the negative plate. Where do they come from? from the electrolyte (sulfuric acid) that as the battery discharges the acid concentration decreases. IF the battery is sitting too long at either a discharge stage or a partial recharge stage, then those crystals can become well fixed on the surface of the negative plate and can never be brought back into solution. This is the reason we recommend a correct recharge and depending on the type of battery, a boost or a certain amount of overcharge to assure not just fully charged plates but crystal dissolution back into the electrolyte. Is this all your battery needs? no. Sulfation is one of the failure modes that is a direct consequence of user ignorance on battery processes. it will naturally occur in the battery and it is engineered to be a determinant cause of failure typically at a point around the warranty time.
More quoted content:
Simple question complicated answer.
I will try to answer as succinctly as possible. Sulphate crystal build-up has been known about since the Lead Acid battery was first invented, and this build-up leads to over 70% of premature failure of lead-acid batteries. However, all batteries wear out over time and no device can stop that happening.
Over the last, 30 years or so battery manufacturers have made great strides in combatting sulphate build-up and improving the life span of their batteries, by introducing changes to the construction of the battery plates, and in ideal circumstances, proper maintenance and correct charging, sulfation should not be a problem. However, we do not live in a perfect world and sulphate build-up remains the major cause of battery failure.It has been found that a controlled overcharge of the battery will break down the crystals, and if used correctly will keep the batteries in good clean condition, and extend the useful life of the battery. This method is not recommended to be used on sealed lead-acid batteries (also known as AGM or VRLA batteries)
Around 20 years ago a simple device that created high voltage pulse sent to the battery was developed, called a pulse generator or desulfator. This, in practice, created the same effect as the controlled overcharge except it was not regulated, so over time, these high voltage pulses damaged the battery plates. This negated the positive effect. The circuit board diagrams for this type of device are freely available on the internet and many of the low-cost devices available today are built using these designs. The short-term solution, long-term damage.
An alternative solution was considered and experimentation showed that if a frequency pulse was sent to the battery it could break down the sulphate build up if the correct frequency could be achieved, however, different frequencies were required for different sizes of crystal that built up on the plates. So the devices using the single frequency method were and still are, hit and miss, some work some worthless. What was needed was a device that would work over a range of frequencies, voltages and size of the battery. Until the last few years of building, this type of device was very expensive (in excess of $1,000) and large (the size of an old-style video player). As no guarantee could be given to the end-user that sulfation was the problem with their battery no companies were prepared to develop them.
Dramatic drops in the size and cost of components have allowed companies to produce small reasonable prices products able to clean the plates of batteries of various capacities and voltages. A small number of manufacturers around the world now produce products that can clean the plates of old batteries and stop the sulphate build-up on new batteries, so recovering them or keeping new batteries clear of the build-up. In effect recovering many old batteries and extend the life of any battery that is not charged or maintained in the correct way. This is ALL they do and is the only thing responsible manufactures claim that their desulfators can do, they cannot recover batteries with any internal damage, shorted cells or AGM batteries that have dried out.
As it is not possible for suppliers to determine the condition or faults of the batteries customers intend to use the device on you should look for suppliers, who give clear information of how to test for faults within the battery or offer a telephone or email service to help with any problems you may have with using a desulfator or with your specific battery setup.
In conclusion, modern multi-frequency desulfators are not a magic bullet that will repair all faulty batteries, but they can significantly extend the life of your lead-acid batteries, and recover a large proportion of batteries that are sulphated and would otherwise be scrapped. This would greatly reduce your replacement battery costs, which is not insignificant on applications like solar storage batteries, ride on golf carts, fork trucks, large boats and motor homes.
This answer is by Dan Hornby product development manager at Battery Extra Ltd. A leading manufacturer of battery management products. The Battery Extra desulfator range covers lead-acid batteries and battery banks from 12 to 120 volts and up to 3,000Ah in capacity. All carry a 60 day 100% refund guarantee and a 3-year warranty. This allows a user sufficient time to try our product and if it does not work for them to return it to us with no financial penalty. More information can be found on the Battery Extra website