Plate sulfidation
Deep discharge will lead to aggravated plate sulfidation of Lead-Acid Batteries. During the discharge process, the active substances on the plates will gradually convert into lead sulfate. When deeply discharged, a large amount of lead sulfate will form coarse, hard and difficult to dissolve crystals on the surface of the plates. These crystals will block the pores of the plates, hindering the full contact between the electrolyte and the active substances inside the plates, thereby reducing the effective reaction area of the plates. As the degree of sulfidation increases, the internal resistance of the battery increases, the battery has difficulty receiving electrical energy during charging, and the battery capacity gradually decreases, eventually leading to a significant reduction in battery performance or even failure.
Plate damage
Deep discharge may also cause physical damage to the plates. Due to excessive discharge, the active substances on the plates may undergo irreversible structural changes, such as plate deformation and active substance shedding. Plate deformation will make the spacing between the plates uneven, increasing the risk of internal short circuits in the battery. The shedding of active substances will lead to a reduction in the effective active substances on the plates, further reducing the capacity and performance of the battery. In severe cases, plate damage may prevent the battery from being charged and discharged normally, and it can only be scrapped.
Electrolyte loss
During deep discharge, the chemical reaction inside the battery consumes a large amount of electrolyte. When the sulfuric acid in the electrolyte is over-consumed, its concentration will decrease, resulting in poor conductivity of the electrolyte. This will not only affect the charging and discharging efficiency of the battery, but may also prevent the battery from reaching a fully charged state during charging, resulting in a false labeling of the battery capacity. The electrolyte loss caused by long-term deep discharge may also expose the plates to the air, accelerate the oxidation and corrosion of the plates, and further shorten the battery life.
Shortened battery life
Combining the above hazards, deep discharge will significantly shorten the service life of Lead-Acid Batteries. Under normal use, the capacity of Lead-Acid Batteries will gradually decrease after multiple charge and discharge cycles, but deep discharge will accelerate the rate of capacity decay. Generally speaking, the life of Lead-Acid Batteries that are frequently deeply discharged may be only half of the life of normal batteries or even shorter. This means that users need to replace batteries more frequently, increasing usage costs and waste of resources. Therefore, when using Lead-Acid Batteries, deep discharge should be avoided as much as possible to extend the battery life and ensure its stable and reliable performance.
