An auto battery is designed for a large short period of current. In which the lost charge is immediately starts to be replaced when engine starts. So there is little chance for Lead sulfate to crystallize.

Deep cycle batteries discharged will have a solution that is saturated with lead sulfate which then if left in this state the lead sulfate will crystallize. It tends to crystallize on the plates acting as a insulator. It does not dissolve in water readily. The strength of the acid is loss in the process.

The plates of both types of batteries are design to be porous. A paste is pressed into the pores. This is done to increase surface area which increases its current abilities. As the battery charges and discharges the plates swell and contract. It forces the paste out. In the deep cycle battery the effect is more damaging.

Even with my limited knowledge of lead acid batteries, it is easy to see that you do not have much of an idea about what you are talking about. Here are a few true and verifiable facts for you (go and search around on the internet for better infos than you already have....):-

Car batteries are designed to give short bursts of very heavy amps and then get recharged. Deep discharging a car battery damages it quite quickly and severely. Even a new battery if fully discharged a few times will not recover. They have a relatively high self discharge rate and a short total life, but are very cheap to buy.

Leisure batteries can be safely completely discharged with little or no damage to them, though it should be stressed that the life will be improved, if not deeply discharged too often. They also have a lower self discharge rate, a longer working life and are more expensive. They cannot supply the so called "cranking amps" that a car battery can, unless the leisure battery is sized far, far bigger than the required normal car battery, which would make it even more expensive......

Can you be more explicit as to what kind of corrosion you are referring to?

One type of corrosion that is common in taxicab, ambulance and some police patrol cars is positive power post corrosion.

This takes place when the excess charge is conducted directly between the positive and negative posts through the electrolyte. It ocurs when the vehicle is idled for long periods of time and he alternator puts out the maximum voltage even though the battery is already fully charged.

As you probably already know when you immerse two electrodes in an electrolyte and then pass a current between them, the positive electrode loses mas and the negative electrode gains some.

It has been noted that the above mentioned kinds of vehicles often suffer premature battery failure and investigators found this common failure mode. The positive post corroded . Other types of damage to batteries have been described as "corrosion" but is in fact something else.

Automotive start batteries have much thinner plates than true deep cycle batteries. As a consequence, these will exhibit plate damage sooner if not cycled properly. Plate fracturing from excess lead sulfate crystalization and plate shedding from use will also be described as "corrosion" due to its similar appearance ( superficially) to plate steel coroding from iron oxide build up, While the surface appearance may look similar the chemical process is very different, and the mechanical action that causes plate deterioation is also different from an iron plate rusting ( corroding).

Generally speaking, thicker plates have more mass and the same extent of sulfation or actual stray current corrosion will not show damage as quickly as it will on thinner plates..

Thanks for the information. I was referring to the internal corrosion that you covered. Other than an external type of electrical device to remove the lead sulfate, is there any other type of additive that will stop or reverse the lead sulfate formation?

BK

Yes and no. First off, you cannot stop lead sulfate formation. This is how you get the electrons out of the battery. Lead sulfate is the natural result of generating electricity in an lead acid cell.

I have heard of several chemical additives that claimed to work in removing crystalized lead sulfate. You have to understand the nature of the electro-chemical activity in a battery. Freshly formed lead sulfate is reversible by charging. But lead suflate crystalizes over time and when crystalized, it is much harder to reverse, sometimes impossible. The desulfator products all claim to act on the sulfate to make it easier to reverse the process during charging.

I was sent samples of a product called BAt cure from India that did seem to work - for a few cycles - but caused plate damage in the longer run. A post mortem disassembly of the battery revealed severe plate erosion in patches. The manufacturer claimed the product "dissolved" the lead sulfate rather than simply softened it, in preparation for reversal back to lead and lead oxide during the next charge cycle.

The conclusion to the test was that the plates used in the so called "deep cycle" battery simply was not thick enough to stand up to the chemical action. True deep cycle batteries have very thick plates. Many batteries sold to consumers claim to be "deep cycle" but in fact are a compromise. the plates are thicker than a starting battery but are not 6 mm or 0.250 inch thick. Used on the right battery it probably would be more effective.

I have had the most sucess with the electronic desulfators. The chemical additives is a one shot thing and if you get it wrong the battery is totally ruined. I would also question how adding a chemical through the fill hole ensures an even and thorough spread throughout all the cell volume of liquid in the absence of stirring.

I wouldn't worry about stiring solutions in a liquid battery. Just watch the gas action when charging.

I appreciate your in depth knowledge and your willingness to help.

BK

Re: "...when you immerse two electrodes in an electrolyte and then pass a current between them, the positive electrode loses mas and the negative electrode gains some."

Apologies, but: sheesh...! or, should I say, "Rubbish!"

First and foremost, you won't "pass a current" unless you have a (metallic) electrical path between those 2 electrodes. With your surrounding electrolyte, then, you now have what is defined by NACE (National Association of Corrosion Engineers, International) as a "Corrosion Cell".

Secondly, electrons in said cell will travel FROM the more electronegative electrode TO the more electropositive electrode via the metallic path. The electrical circuit will be completed by the "holes" provided by the positive ions in the electrolyte (hydrogen ions, in acids)... The electronegative electrode (the anode) will LOSE mass, as it gives-up electrons, subsequently shedding ions into the electrolyte. The electropositive electrode (the cathode) will gain mass (so negligible, though, you'll never actually measure it).

Now where's the [Start-Over] button for this thread........?!

---------------------------------------------------------------

When these are connected to a charging source, the reaction is reversed from your description.

I was not describing a galvanic cell but the effects when the battery is connected to a source of current like a charger.