Before diving in deep cycle battery corrosion we want to define Corrosion process. Corrosion or the oxidation of the deep cycle battery’s grid (where corrosion mostly happens) occurs when two dissimilar materials in the same electrolyte are connected electronically and reactions occur at each material ,result in causing plate growth and eventually destroys the deep cycle battery’s grid.
In our case we take about positive electrode that consist of active positive material PbO2 , Pb grid material and acid – H2SO4 act as electrolyte.
One of the factors that limit the cycle life of the deep cycle battery is corrosion process that is taking place between the positive grid material and the positive active. Corrosion leads to grid oxidation that support the active positive material result in grid ruin which it either transmit or receive the current from or to grid and it will proceed continuously during ﬂoat charge and shorten the lifetime of the deep cycle battery and then leads to end of the service life to the situation that the current conductor (lead) is almost no longer available , (figure 1).
This phenomenon is also called premature capacity loss; this reaction not only decreases the positive grid conductivity but also consumes the water , and leads to the growth of the positive plates , the grid wires do not have the mechanical force due to the degree of corrosion. Corrosion lead to potential differences of the positive and the negative electrode, result in self-discharge and faint performances of deep cycle battery .
Deep Cycle Battery Corrosion Reasons
1- Continuous operation at high temperatures particularly above 55C may reduce life as a result of an increase in the rate of deep cycle battery’s corrosion
2- Excessive overcharging leads to increasing positive grid corrosion, and this is manifested as ‘‘growth’’ or expansion of the grid.
3-Moisture and dirt on top of and between cells permits stray intercell currents, resulting in corrosion through electrolysis.
4- Denser acid tends to form at the bottom of the deep cycle battery. especially in the space below the plates, this can cause increased corrosion.
5- The repeated charging and discharging of the deep cycle battery shortens the battery life through heat generation and corrosion.
Industrial Esteems to Resist Deep Cycle Battery Corrosion
1-Tubular plate types have a good corrosion resistance.
2- The pure lead provides a high corrosion resistance and an extremely long service life.
3- Use of pure or special alloy lead result in corrosion resistant increasing.
4- A light coating of petroleum jelly is used Intercell to prevent corrosion .
Recommendations to Preserve A deep Cycle Battery
1- Keeping the deep cycle battery clean and dry, particularly top of the battery will minimize corrosion of cell post connectors and steel trays.
2- Keep the batteries from rain water that could cause corrosion on the terminals of the batteries
3- A coating of no-oxide anti-corrosive grease on terminals will usually prevent corrosion.
4-A low charge current is desirable to minimize overcharge, grid corrosion associated with overcharge.
5-It is important to control the charge to maintain the morphology of the electrode, to prevent a rise in the temperature, particularly to a point where deleterious side reactions (corrosion) take place.
6- Overﬁlling must be avoided because the resultant overﬂow of acid electrolyte will cause tray corrosion, ground paths, and loss of cell capacity.