The study shows that the acceptable charging curve of the battery is shown in figure l if the minimum exhaust rate is taken as the premise during charging. The experimental results show that if the charging current changes according to the curve shown in figure l, the charging time can be greatly shortened, and the capacity and life of the battery are not affected. Therefore, this curve is called the optimal charging curve. As can be seen from figure 1, the initial charging current is very large, but press, I=Ioe investment t decreases rapidly with time. The main reason is the polarization phenomenon of the battery at two poles during charging.
During the charging process of sealed battery, oxygen and hydrogen are generated internally. When oxygen cannot be absorbed in time, it accumulates on the positive plate (positive plate generates oxygen), causing the area of positive plate to shrink relatively, the internal pressure of the battery increases, and the temperature rises, showing the rise of internal resistance, that is, the so-called "polarization" phenomenon occurs. The charge and discharge of the battery is reversible. The chemical reaction formula of its charging and discharging is as follows:
PbO2 + 2 - h2so4 + Pb = PbSO4 + 2 h2o + PbSO4
Obviously, the charging process and the discharge process are mutually reversible, which is essentially a thermodynamic equilibrium process. To ensure that the battery is always charged in a balanced state, the charging current through the battery should be as small as possible. For this reason, the ideal charging mode should be that the external charging voltage equals to the electromotive force of the battery itself. However, practice shows that, due to the differences of various factors such as electrode materials and solution concentration, when the battery is charged, the applied voltage must increase and exceed the equilibrium electromotive force of the battery, which is also the inevitable result of polarization.
