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Common causes of sulfation of battery plates


Time:

2021-06-07

Excessive discharge causes more lead sulfate to be generated in the deep layer of the electrode plate, which agglomerates and adheres to the deep pores of the active material, so that it is not easy for normal charging to fully act on the inner layer of the plate to reduce it.

1. Excessive discharge of the battery or deep discharge of small current

Excessive discharge causes more lead sulfate to be generated in the deep layer of the electrode plate, which agglomerates and adheres to the deep pores of the active material, so that it is not easy for normal charging to fully act on the inner layer of the plate to reduce it.

2, the battery lacks regular overcharge or often undercharge

When the battery lacks regular overcharge, or is often insufficient, more or less unreduced lead sulfate remains in the active material. Over time, it will be difficult to completely convert this lead sulfate into active material, causing serious vulcanization. .

3, the battery has been in a half-discharged or discharged state for a long time

The battery has been in a half-discharged or discharged state for a long time. For example, when it is in a state of leakage, it has been discharged or is still self-discharged. Therefore, the density of the electrolyte is low, and the small lead sulfate crystals are easily dissolved in the electrolyte. Lead phosphate crystals are not only difficult to dissolve, but are connected to each other and continue to increase (more obvious in the case of large environmental temperature changes).

This different process of change leads to recrystallization, which leads to the formation of many large pieces of lead sulfate on the electrode plate.

4. Lack of electrolyte

The liquid level is too low (the liquid level on the electrode plate is too low), the upper part of the electrode plate cannot work with the electrolyte during charging, and the recovery cannot be obtained for a long time, causing the upper part of the electrode plate to be vulcanized.

5. The amount of electrolyte is too small

The use and maintenance of lead-acid batteries is not good, the electrolyte volume is too small, so that the electrode plate is exposed to the liquid surface, and the lead sulfate on the upper electrode of the electrode plate cannot electrochemically interact with the electrolyte during charging, and the effective material of the electrode plate cannot be fully recovered.

6, the electrolyte specific gravity is too high or the temperature is too high

The specific gravity of lead-acid battery electrolyte is too high or the temperature is too high, and lead sulfate will be deeply formed and difficult to recover.

In addition, with the change of temperature, the dissolution and crystallization of lead sulfate in the electrolyte are alternately carried out, which promotes and facilitates the formation of large grains of lead sulfate; if the temperature is too high, lead sulfate will form deeply and cannot be recovered.

7. Not charging in time after discharging

After the battery is discharged, it is not charged in time (the delay time exceeds 24 hours), etc.

8. The impure impurities in the electrolyte exceed the specified value

The impure sulfuric acid electrolyte of lead batteries not only promotes the self-discharge of the battery, but also is the main cause of irreversible sulfation of the plates.

Because there are some "surface active materials" in the sulfuric acid electrolyte, and these "surface active materials" exist as impurities in the electrolyte, or from separators, electrode active materials, and from contact with the electrolyte. Leached from other materials.

If these "surface active substances" are adsorbed on the surface of lead sulfate, it will slow down the dissolution rate of lead sulfate and limit the cathode reduction of lead ions (Pb++) during charging.

If the "surface active material" is adsorbed on the metallic lead, the energy of lead to form nuclei on the surface of the spongy lead is increased during charging (that is, the precipitation overpotential of lead is increased), so that the charging cannot be performed normally.

Note that the adsorption on the positive electrode can only cause a fairly slight irreversible sulfation. This is due to the anodic polarization when the positive electrode is charged, and the potential value is sufficient to oxidize the "surface active material".

Therefore, it has little effect on the positive plate. The problem of sulfation of the battery plate mainly lies in the negative plate.