After the battery is put into use, it must be charged and discharged regularly. The purpose of charging is to restore the storage capacity of battery in time to meet the needs of electrical equipment. The purpose of discharge is to test the battery capacity parameters in time and promote the activation reaction of electrode active substances. The charging and discharging conditions of the battery will directly affect the electrical performance and service life of the battery. At present, there are many ways to charge the battery. Choosing a scientific and reasonable charging method will greatly improve the maintenance effect of the battery.
1. Constant current charging method
In the process of charging, the charging current always remains the same, which is called constant current charging method, or constant current charging method for short. In the charging process, as the battery voltage increases gradually, the charging current decreases gradually. In order to keep the charging current from decreasing as the battery terminal voltage increases, the power supply voltage must be increased gradually in the charging process, so as to maintain the charging current unchanged all the time. This requires a high degree of automation of the charging equipment, and the general simple charging equipment cannot meet the requirements of constant current charging. Constant current charging method, in the case of the maximum allowed charging current of the battery, the greater the charging current, the shorter the charging time. If time is taken into consideration, it is advantageous to adopt this method. However, if the charging current is still the same in the later stage of charging, at this time, because most of the current is used in electrolytic water, the electrolyte bubbles are too much and appear boiling, which not only consumes electric energy, but also easily causes a large number of active substances on the plate to fall off, the temperature rise is too high, resulting in plate bending, rapid capacity decline and early scrapping. Therefore, this charging method is rarely used.
2. Constant voltage charging method
In the process of charging, the charging voltage remains constant all the time, which is called constant voltage charging method, or constant voltage charging method for short. Since the constant voltage charging starts to the later stage, the power supply voltage is always kept constant, so the charging current at the beginning of charging is quite large, which greatly exceeds the normal charging current value. However, with the charging process, the battery terminal voltage increases and the charging current decreases. When the battery terminal voltage and the charging voltage are equal, the charging current is reduced to the minimum or even zero. It can be seen that the advantage of constant voltage charging method is that it can avoid the loss of active materials and electric energy caused by excessive charging current in the later stage of charging. But its disadvantage is that at the beginning of charging, the charging current is too large, the volume of the active material changes and shrinks too fast, which affects the mechanical strength of the active material and causes it to fall off. In the later stage of charging, the charging current is too small, so that the active substances in the deep of the plate can not get the charging reaction, forming a long-term charge shortage, which affects the service life of the battery. Therefore, this charging method is generally only suitable for the special occasions without distribution equipment or simple charging equipment, such as the charging of batteries on the car, and the charging of small batteries of No. 1 to No. 5 dry cell type adopts the equal voltage charging method. When the constant voltage charging method is used to charge the battery, the required power supply voltage is about 2.4-2.8v for each single cell of the acid battery and about 1.6-2.0v for each single cell of the alkaline battery.
3. Constant voltage charging with fixed resistance
A method used to remedy the shortcomings of constant voltage charging. That is, a resistor is connected in series between the charging power supply and the battery, so that the current at the initial stage of charging can be adjusted. But sometimes the maximum charging current is limited, so with the charging process, the battery voltage gradually rises, but the current almost becomes a linear attenuation. Sometimes two resistance values are used, at about 2.4V, to change from low resistance to high resistance to reduce outgassing.
4. Stage equal current charging method
Combined with the characteristics of constant current and constant voltage charging method, the battery uses a large current at the initial stage of charging. After a period of time, it uses a smaller current, and then it uses a smaller current at the later stage of charging. That is to say, the method of constant current charging with different current in different stages is called stage constant current charging method. The stage constant current charging method can be generally divided into two stages or multiple stages. The stage constant current charging method needs short charging time and good charging effect. In the later stage of charging, a smaller current is used to charge, which reduces the flushing of the active material on the plate by bubbles and reduces the falling off of the active material. This kind of charging method can prolong the service life of battery, save electric energy, and charge thoroughly, so it is a commonly used charging method at present. Generally, the first stage of the battery is charged with a current of 10h, and the second stage is charged with a current of 20h. The charging time of each stage is right or wrong, and the specific requirements and standards of various batteries are different.
5. Floating charge method
The intermittent battery or the battery only used in case of AC power failure shall be charged by floating charge. Floating charging method is generally used to charge the fixed battery in some special occasions. The advantage of floating charge method is that it can reduce the outgassing rate of the battery and prevent overcharge. At the same time, because the battery is powered in parallel with DC power supply, when the electric equipment is powered by large current, the battery outputs large current instantaneously, which is helpful to calm the voltage of the power supply system and use the electric equipment normally. The disadvantage of floating charge method is that the charge of individual battery is unbalanced and under charged, so it needs to be charged regularly.