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Common Problem


Common faults of battery 2023-06-01 10:11:58.154

Battery vulcanization: A layer of large white hard crystals is formed on the surface of the negative plate inside the battery, which cannot be peeled off after charging, nor can it be converted into lead sulfate as an active material. This is called irreversible sulfation, or "vulcanization" for short.

Reasons for vulcanization: 1. The battery is under-charged for a long time or not charged in time after being discharged. 2. Long-term excessive discharge or low current deep discharge. 3. Because the battery loses water or the electrolyte concentration is too high, the composition is not pure. 4. The external temperature changes sharply. The performance is: the battery runs out after being fully charged.

The external faults mainly include shell cracks, pole corrosion, pole looseness, and dry cracking of the sealant; while internal faults mainly include pole plate vulcanization, active material shedding, pole plate grid corrosion, pole plate short circuit, self-discharge, and pole plate arching.

One, plate vulcanization

The phenomenon that a layer of white coarse-grained PbSO4 formed on the battery plate cannot be converted into PbO2 and Pb during normal charging is called "lead sulfate hardening", that is, "vulcanization". This kind of coarse-grained lead sulfate has poor conductivity and is difficult to restore under normal charging. The coarse grains and large volume block the pores of active materials, hinder the penetration of electrolyte, and increase the internal resistance of the battery.

1, failure phenomenon

① The battery capacity drops rapidly during discharging, and the single cell voltage drops rapidly when tested with a high-rate discharge meter;

② The density of the electrolyte drops below the specified normal value;

③ The voltage of the battery is too high at the beginning of charging and when the charging is completed, which can reach more than 2.7V;

④ When the battery is charging, the electrolyte temperature rises too fast, easily exceeding 45 ℃; at the same time, bubbles are generated prematurely, even at the beginning of charging;

⑤ Hard, insoluble large white particles are formed on the plate.

2, the cause of the failure

① The battery is under-charged for a long time or is not charged in time after discharge, causing a part of the lead sulfate on the electrode plate to dissolve in the electrolyte. The higher the ambient temperature, the greater the solubility. When the ambient temperature decreases, the solubility decreases, and the dissolved lead sulfate will re-precipitate and crystallize again on the plate.

② The accumulator is often over-discharged or low-current deep-discharge, resulting in the formation of lead sulfate in the inner layer of the small pores of the electrode plate, and it is not easy to recover from charging.

③ If the electrolyte level is too low, the active material on the upper part of the electrode plate is exposed to the air to be oxidized. The fluctuation of the electrolyte when the car is running makes it contact with the oxidized active material, producing coarse-grained lead sulfate.

④ If the initial charge is not complete or regular supplementary charge is not performed, so that it can be used for a long time in a semi-charged state, the discharge product lead sulfate on the electrode plate will exist for a long time, and it will also form coarse particles through recrystallization.

⑤ If the electrolyte density is too high or impure, the battery will discharge by itself, and lead sulfate will be produced, which will provide the material basis for the recrystallization of lead sulfate.

3. Measures

① Slightly vulcanized, can be charged with a low current of 2-3A for a long time, that is, overcharge; or use full discharge and full charge to reduce the active material; it can also be eliminated by desulfurization charging

②When the vulcanization is serious, it should be scrapped and replaced;

③ Keep the battery always in a fully charged state:

A, the battery on the car is regularly sent to the charging room to be fully charged;

B. The discharged battery shall be charged in the charging room within 24h.

④The height of the electrolyte should meet the regulations.

2. Self-discharge

The phenomenon that the battery automatically disappears when there is no load is called self-discharge.

1, fault characteristics

Ordinary batteries will have a certain degree of self-discharge due to their own structure. However, if the capacity self-discharge per day and night does not exceed 2% C20, it belongs to normal self-discharge; if the self-discharge volume per day and night exceeds 2% C20, it belongs to faulty self-discharge.

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.

The faults in the use of lead-acid batteries can be divided into external faults and internal faults according to the location.

1) External failure: shell crack, pole pile corrosion, pole pile looseness and sealant dry crack.

2) Internal failures: plate vulcanization, self-discharge, plate short circuit, active material shedding, plate grid frame corrosion and plate arching.

Common internal failures of lead-acid batteries:

1. Plate vulcanization

Failure phenomenon:

1) The battery capacity is reduced, and the single-cell voltage drops rapidly.

2) The density of the electrolyte drops below the specified normal value.

3) The voltage of the battery is too high at the beginning and the end of the charge, which can reach more than 2.7v.

4) The battery generates bubbles prematurely during charging, and even has bubbles at the beginning of charging.

5) The electrolyte temperature rises too fast when charging the battery, easily exceeding 45°C.

6) The voltage drops too fast when the battery is discharged (discharge with a low discharge rate), and it drops to the end voltage prematurely.

7) Generate hard, insoluble, large white particles on the plate.

cause of issue:

1) The battery is placed in the discharged and half-discharged state for a long time. Because the lead sulfate has a large temperature difference between day and night, the two opposite processes of dissolution and crystallization in the electrolyte continue to occur alternately, resulting in recrystallization. When crystallized, coarse and insoluble lead sulfate crystal grains are formed on the electrode plate.

2) The accumulator is often over-discharged or deeply discharged with a small current, so that lead sulfate is generated in the inner layer of the small pores of the electrode plate, and it is not easy to recover from charging.

3) The electrolyte level is too low, and the active material on the upper part of the electrode plate is exposed to the air to be oxidized. When the car is running, the fluctuation of the electrolyte makes it contact with the oxidized active material, producing coarse-grained lead sulfate.

4) The initial charging is not complete or regular supplementary charging is not performed. The initial charge of the battery is not complete or the regular supplementary charge is not performed during use, so that it can be used for a long time in a semi-charged state. The discharge product lead sulfate on the electrode plate will exist for a long time, and it will also form coarse particles through recrystallization.

5) The battery self-discharge due to impure electrolyte or other reasons will produce lead sulfate, thereby providing a material basis for the recrystallization of lead sulfate.

troubleshooting:

If the battery has a mild vulcanization failure, it can be charged with a low current of 2~3A for a long time, that is, overcharge; or use a full discharge and full charge cycle method to reduce the active material; it can also be eliminated by desulfurization charging. Severely vulcanized batteries should be scrapped.

How does temperature affect voltage?

The temperature rises, the voltage drops; the temperature drops, the voltage rises.

Can the battery be used up before charging it?

Hurry up and power it is recommended to charge the battery when the battery power is lower than 80% of the rated power storage capacity.

How does temperature affect the specific gravity of the electrolyte?

The temperature rises, the electrolyte volume expands; the temperature decreases, the electrolyte volume shrinks. Therefore, the temperature reading must be corrected when measuring the specific gravity.

What is the maximum temperature limit for charging?

Lead-acid battery charging temperature cannot exceed 120 degrees Fahrenheit (48.9 degrees Celsius). When the temperature reaches this degree, the battery should be cooled to continue charging.

Will the battery be discharged when not in use?

All batteries, regardless of their chemical characteristics, will have self-discharge. The self-discharge rate depends on the battery type and the temperature of the battery storage location. TROJAN batteries have a weekly self-discharge rate of about 4% at 80 degrees Fahrenheit.

Will the battery freeze?

The battery is in a partially discharged state, and the electrolyte will freeze. The battery will freeze when the self-discharge is above 40% and the temperature is lower than 6 degrees Fahrenheit; the freezing temperature of a fully charged battery is -92 degrees Fahrenheit.

How does temperature affect the performance of the battery?

Higher temperature (above 77 degrees Fahrenheit, or 25 degrees Celsius), the battery's storage capacity increases, but it will shorten the battery life. Higher temperature will also increase self-discharge at the same time, lower battery temperature (below 25 degrees Celsius) will reduce the battery's storage capacity but at the same time extend the battery life. Lower temperature will also reduce self-discharge. Therefore, use the battery at about 25 degrees Celsius to obtain the best battery performance and life.

What are the most common mistakes made by battery users?

Lead-acid battery is undercharged: usually after using the battery, the battery cannot be fully charged. Continued under-charging or not storing the battery fully charged can cause sulfates to accumulate on the plates-usually called salinization. This will reduce the performance of the battery and cause permanent damage to the battery, as well as the "stratification" phenomenon.

Overcharge: Continuous charging will accelerate the corrosion of the positive plate and the consumption of water.

Insufficient moisture: In long-term use, the moisture in the battery will be lost during the charging process. If the electrolyte level is lower than the top of the electrode plate, irreparable damage will occur. The liquid level should be checked frequently.

Too much water: Adding too much water will cause electrolyte overflow and affect battery performance. At the same time, adding water before charging will also cause electrolyte overflow