(1) The chemical reaction process of lead-acid batteries is
PbO2+2H2SO4+Pb[discharge (primary battery)] ⇌[charge (electrolytic cell)] 2PbSO4+2H2O
Among them, PbO2 is the anode, Pb is the cathode, and H2SO4 is the electrolyte, which constitutes the battery as shown in Figure 1(a). Due to the high potential of PbO2, the potential difference between the two poles can ionize the H2SO4 between the poles into positively charged hydrogen ions and negatively charged sulfate ions, respectively, to synthesize lead sulfate with the two polarizations, generating an open circuit voltage, such as an external load resistance, then The flow of electrons flows from the negative electrode to the positive electrode, and the battery discharges. At this time, it is a DC energy source. During the discharge process, the concentration of sulfuric acid decreases and the open circuit voltage is reduced. Therefore, water and sulfuric acid are often added. If the externally connected two-stage is not a load resistance but a DC power supply higher than the open circuit voltage, the current reverse chemical reaction proceeds in the reverse direction, and the positively charged hydrogen ions and the negatively charged sulfate ions are polymerized and reduced to PbO2 and Pb. Hydrogen and water vapor are to be precipitated, so the charging current cannot be too large especially in the later stage of charging. The currently used sealed maintenance-free valve-controlled high-efficiency lead-acid battery is to change the electrode and diaphragm materials and the sealing valve control to solve the loss of water and the escape of hydrogen, as shown in Figure 1(b), in order to achieve the purpose of maintenance-free.
(2) The basic characteristics of lead-acid batteries. The basic characteristic of lead-acid batteries is to produce a certain value of open circuit voltage at the two poles, and its value is related to the electrolyte concentration, as shown in Figure 2(a). When the DC load is connected to work, see Figure 2(b). The battery is in a discharged state, and the voltage drops rapidly at the beginning of the work (AB), and then enters a stable working period, the voltage drops slowly (BC), and the voltage starts after a certain period of time. Rapid decline (CD), at this time should stop working to charge. The charging curve is shown in Figure 2(c). The voltage rises faster in the initial charging stage, then slows down, and the voltage rises faster in the final stage. When charging, use 0.1C high current fast charge (not greater than 0.2C, such as 100A·h battery not greater than 20A), after a certain period of time, use low current and constant voltage to slowly charge for about 6 hours, and then float to a lower current with a smaller current in the later stage of charging. high voltage. Try not to use high current fast charge, and use small current float charge in the constant voltage section to improve battery life. When using lead-acid batteries, do not wait until the power is exhausted before charging. Replenishing the battery at any time can extend its service life. Continuously floating the lead-acid batteries with on-board solar batteries will not only save energy, but also prolong the service life of the batteries.
(3) The chemical reaction and structure of lead-acid batteries. The charge and discharge process of lead-acid batteries is an electrochemical process, and its basic principles and chemical reactions are shown in Figure 3(a). In the discharging state, the main components of the positive and negative electrodes are lead sulfate. It is necessary to add water frequently and exhaust gas when used. The safety is poor and the maintenance amount is large. After nearly 150 years of development, lead-acid batteries have made considerable progress and development in all aspects. The structure of valve-regulated sealed maintenance-free lead-acid batteries used in solar batteries is shown in Figure 3(b). Due to its own structural advantages, sealed valve control, chemical reaction self-circulation, safe and environmentally friendly use, long life, no maintenance, The consumption of electrolyte is very small, and there is basically no need to supplement distilled water during the service life.
(4) The operating characteristics of the battery. The main operating parameters of a battery are open circuit voltage and capacity. Generally, multiple storage units are connected in series and parallel to form a component battery body, and the voltage and capacity are marked on the body. For example, 12-120 means a 12V-120A·h battery. These two parameters will change during use, and the changes of various types of batteries will be different, which is called operating characteristics. The operating characteristics of a certain battery are shown in Figure 4. It can be seen from the figure that the larger the storage capacity of the battery, the higher the output voltage; the greater the depth of discharge, the shorter the life, so the solar car can be charged as it is used, and maintaining a small depth of discharge will greatly increase the battery life; The higher the temperature, the more the capacity will be reduced. Pay attention to cooling down during use.
