(1) Principle of charging and discharging of lead-acid battery when charging and discharging lead-acid battery, positive and negative active substances and electrolyte participate in chemical reaction at the same time. The principle equation of charging and discharging chemical reaction of lead-acid battery is as follows.
Positive electrode: PbO2 + H2SO – → PbSO + H2O
Negative electrode: Pb + H2SO → PbSO + H2
Total reaction: PbO2 + 2h2so4 + Pb = = 2 pbso2 + 2H2O
It can be seen from the above chemical reaction equation that when the lead-acid battery is discharged, the active material lead dioxide of the positive electrode and the active material metal lead of the negative electrode react with the sulfuric acid electrolyte to form lead sulfate. Electrochemically, this reaction is called “bisulfate reaction”. At the end of the battery discharge, the lead sulfate converted from the positive and negative active substances is a substance with loose structure and fine crystal, and the degree of activity is very high. In the process of battery charging, the loose and fine lead sulfate on the positive and negative electrodes will become lead dioxide and metal lead again under the action of external charging current, and the lead-acid battery is fully charged. It can be seen that the above reaction is reversible. It is this reversible electrochemical reaction that enables the battery to store and release electric energy. In daily use, people usually use the discharge function of the battery and take the charging stage as the maintenance of the battery. The lead-acid battery can maintain the activity of chemical substances in the battery for a long time when it is fully charged. After the battery is discharged, if it is not fully charged in time, the active substances in the battery will soon lose activity, resulting in irreversible chemical reaction in the battery. Therefore, whether solar battery or lead-acid battery for other purposes, the battery should be fully charged and stored, and the battery should be supplemented regularly. Want to know more about battery charging? click here to open。
(2) Management during charging
① After the battery temperature is charged, touch the shell of the battery with your hand immediately, which means that the temperature will rise during charging. However, if the temperature (electrolyte temperature) rises too high, the service life of the battery will be significantly shortened. This is because the temperature of the battery increases, the active substances on the cathode and anode plates will deteriorate, the anode lattice will be corroded, and the service life of the battery will be shortened. The temperature of the battery should not be too low. If the temperature is too low, the capacity of the battery will be reduced, it is easy to discharge excessively, and the service life of the battery will be shortened. Generally, the electrolyte temperature of the battery shall be maintained at
The ideal use state of 15 ~ 55 ℃ can not exceed 15 ~ 55 ℃ during discharge and charging under special circumstances
0 ~ 60 ℃. At the end of discharge, it is best to maintain the electrolyte temperature below 40 ℃.
② The ratio of charging capacity to discharge capacity of the battery shall not be too high. If it is too high, it is easy to decompose water, produce gas and significantly reduce the electrolyte, which will increase the temperature during charging and shorten the service life of the battery. When the ratio of charge to discharge is 120%, the service life of the battery is 4 years; When the charge to discharge ratio of the battery reaches 150%, the service life of the battery is only 3.2 years. In addition, insufficient charging and repeated discharge will seriously affect the service life of the battery.
③ The gas charging place must be well ventilated and away from the fire source to avoid electric shock. The gas produced during charging is oxygen and hydrogen. Hydrogen is flammable and explosive. If the hydrogen content in the air reaches more than 3.8% and is close to the fire source, explosion will occur.
(3) Management during discharge: the internal impedance of the battery will increase when discharging. If it is doubled when fully charged, it will increase by 2 ~ 3 times when fully discharged. It is forbidden to continue discharging when reaching the rated voltage, because the deeper the discharge, the higher the temperature in the battery, the more serious the deterioration of active substances, and thus shorten the service life of the battery. Therefore, if the battery voltage has reached the maximum voltage specified by the manufacturer, it should be stopped and charged immediately. When charging and discharging repeatedly every day for use, the battery life will be affected by the depth of discharge.
The electrolyte density of the battery is almost proportional to the discharge. Therefore, the discharge capacity of the battery can be calculated according to the density when the battery is fully discharged and the density when 10% of the battery is discharged. The electrolyte density of lead-acid battery is almost proportional to the discharge. Therefore, the density of electrolyte after the battery is used should be measured regularly to avoid excessive discharge. While measuring the density, also measure the temperature of the electrolyte. The density converted by 20 ℃ shall prevail. Do not reduce it to less than 80% of the discharge.
① Discharge state and internal impedance the internal impedance will increase due to the increase of discharge capacity, especially at the end of discharge, the impedance is the largest, which is mainly due to the decrease of the density of lead sulfate and electrolyte, the bad conductor generating current in the electrode plate, resulting in the increase of internal impedance. Therefore, after discharge, be sure to charge immediately. If it is allowed to discharge continuously, After lead sulfate forms a stable white crystal (i.e. the vulcanization phenomenon mentioned in the literature), even if it is charged, the active material of the electrode plate cannot be restored to its original state, and the service life of the battery will be shortened.
② Temperature during discharge when the battery is over discharged, the internal impedance increases significantly, and the battery temperature will soon lose its activity, resulting in irreversible chemical reaction inside the battery. Therefore, whether solar battery or lead-acid battery for other purposes, the battery should be fully charged and stored, and the battery should be supplemented regularly.
(2) Management during charging
① After the battery temperature is charged, touch the shell of the battery with your hand immediately, which means that the temperature will rise during charging. However, if the temperature (electrolyte temperature) rises too high, the service life of the battery will be significantly shortened. This is because the temperature of the battery increases, the active substances on the cathode and anode plates will deteriorate, the anode lattice will be corroded, and the service life of the battery will be shortened. The temperature of the battery should not be too low. If the temperature is too low, the capacity of the battery will be reduced, it is easy to discharge excessively, and the service life of the battery will be shortened. Generally, the electrolyte temperature of the battery shall be maintained at
The ideal use state of 15 ~ 55 ℃ can not exceed the range of 15 ~ 55 ℃ during discharge and 0 ~ 60 ℃ during charging under special circumstances. At the end of discharge, it is best to maintain the electrolyte temperature below 40 ℃.
② The ratio of charging capacity to discharge capacity of the battery shall not be too high. If it is too high, it is easy to decompose water, produce gas and significantly reduce the electrolyte, which will increase the temperature during charging and shorten the service life of the battery. When the ratio of charge to discharge is 120%, the service life of the battery is 4 years; When the charge to discharge ratio of the battery reaches 150%, the service life of the battery is only 3.2 years. In addition, insufficient charging and repeated discharge will seriously affect the service life of the battery.
③ The gas charging place must be well ventilated and away from the fire source to avoid electric shock. The gas produced during charging is oxygen and hydrogen. Hydrogen is flammable and explosive. If the hydrogen content in the air reaches more than 3.8% and is close to the fire source, explosion will occur.
(3) Management during discharge: the internal impedance of the battery will increase when discharging. If it is doubled when fully charged, it will increase by 2 ~ 3 times when fully discharged. It is forbidden to continue discharging when reaching the rated voltage, because the deeper the discharge, the higher the temperature in the battery, the more serious the deterioration of active substances, and thus shorten the service life of the battery. Therefore, if the battery voltage has reached the maximum voltage specified by the manufacturer, it should be stopped and charged immediately. When charging and discharging repeatedly every day for use, the battery life will be affected by the depth of discharge.
The electrolyte density of the battery is almost proportional to the discharge. Therefore, the discharge capacity of the battery can be calculated according to the density when the battery is fully discharged and the density when 10% of the battery is discharged. The electrolyte density of lead-acid battery is almost proportional to the discharge. Therefore, the density of electrolyte after the battery is used should be measured regularly to avoid excessive discharge. While measuring the density, also measure the temperature of the electrolyte. The density converted by 20 ℃ shall prevail. Do not reduce it to less than 80% of the discharge.
① Discharge state and internal impedance the internal impedance will increase due to the increase of discharge capacity, especially at the end of discharge, the impedance is the largest, which is mainly due to the decrease of the density of lead sulfate and electrolyte, the bad conductor generating current in the electrode plate, resulting in the increase of internal impedance. Therefore, after discharge, be sure to charge immediately. If it is allowed to discharge continuously, After lead sulfate forms a stable white crystal (i.e. the vulcanization phenomenon mentioned in the literature), even if it is charged, the active material of the electrode plate cannot be restored to its original state, and the service life of the battery will be shortened.
② Temperature during discharge when the battery is over discharged, the internal impedance increases significantly and the battery temperature will also rise. Therefore, it is best to control the temperature below 40 ℃ at the end of discharge.
a. Oxygen overflows from the positive electrode, and the oxygen generated by the positive electrode is easy to be reduced at the negative electrode, that is:
Pb+O+H:SO.— H.0+PbSO。
It is easy to promote the autolysis of lead in the negative electrode.
b. There are metal impurities on the surface of the negative electrode. If the hydrogen Superpotential value (hydrogen precipitation Superpotential) of these impurities (lead, ladder and silver) is low, they can form an energy storage micro battery with the active material at the negative electrode, so as to accelerate the autolysis rate of lead.
c. The influence of impurities in electrolyte and micro battery produced by negative active material also promote the autolysis of negative lead. When the battery generates PbSO4 in the discharge state, some of it will sink and become irreducible PbSO4 (only when PbSO4 can be successfully reduced to Pb and PbO2 during charging, the service life of the battery will be long), which shortens the service life of the battery. In addition, PbSO. The sinking of the battery will often cause a short circuit inside the battery.
(4) Self discharge of storage battery during open circuit storage, its capacity will gradually decrease, which is called self discharge.
① The self discharge generated by the positive electrode mainly includes the following aspects.
a. Oxidation of metal ladder, metal lead and metal silver in positive grid.
Pb+Sb+2H2SO2——PbO2+SbO2+2SO2+2H2O
PbO2 + Pb (grid) + 2h2so4 — 2pbso4 + 2H2O
PbO2+2Ag+2 H2SO4——PbSO4+Ag2SO4+2H2O
b. The concentration difference caused by the concentration difference between the pore depth of the plate and the sulfuric acid concentration on the outer surface of the plate will cause self discharge, which gradually decreases with the shelf time after charging.
c. Effect of hydrogen produced by negative electrode:
PbO2+H2+H2SO4——PbSO4+2H2O
d. Influence of impurities in separator electrolyte: if there are impurities easy to be oxidized in separator or electrolyte, it will cause the reduction of positive active material and produce self discharge.
e. Influence of iron ions in the positive active material: if there are divalent iron ions in the positive active material, they will be oxidized to trivalent iron ions, resulting in the reduction of the positive active material.
PbO2+3H++HSO4-+2Fe2+——PbSO4+2H2O+2Fe3+
② Self discharge generated by the negative electrode because the negative active material lead is an active metal powder electrode. In sulfuric acid solution, the electrode potential is negative than that of hydrogen, and the reaction of replacing hydrogen can occur. This phenomenon is usually called lead autolysis. In principle, the reaction is as follows: Pb + H2SO4 → PbSO4 + H2.
There are the following aspects affecting the autolysis rate.
a. The rate of lead autolysis increased with the increase of sulfuric acid concentration and electrolyte temperature.
b. Influence of metal impurities on the negative surface of the battery there are various metal impurities on the negative surface. When the hydrogen Superpotential value (hydrogen precipitation Superpotential) of a metal impurity is low, it can form a corrosive micro battery with the negative active material, so as to accelerate the autolysis rate of lead. For example, the presence of ladder, iron, silver and other metals, especially iron, has a great impact.
At the negative electrode: Pb+HSO4—+2Fe3+======PbSO4+H++2Fe2++ 2fe3 +
At the positive electrode: PbO2 + 3H + + hso-4 + 2fe2 + = = PbSO4 + 2H2O + 2fe3+
c. Influence of oxygen precipitated from the positive electrode the oxygen precipitated from the positive pboz reaction is easy to be reduced and absorbed at the negative electrode, that is:
Pb+1/2O2+H2SO4——PbSO4+H2O
So as to promote the autolysis of negative lead.
d. The influence of impurities in the separator and electrolyte the micro battery produced by the metal impurities contained in the separator and electrolyte and the negative active material promotes the autolysis of negative lead.
Read more: What is the composition and function of a solar array?
