The battery internal resistance variation characteristics
In the daily maintenance and the use process, want to know the capacity of the battery, or the battery charged online running state, can push know battery capacity through battery internal resistance change. ( l） The composition of battery internal resistance of battery internal resistance roughly divided into the ohmic resistance and the polarization resistance. Ohm internal resistance is mainly composed of polar plate, a column, the resistance of the electrolyte, separator; The polarization resistance is a chemical polarization and concentration polarization resistance. When lithium battery fully electric resistance minimum at this moment, internal resistance increases with increasing discharge, use of the properties, determination of battery internal resistance can understand the battery charged. (1) the diaphragm resistance lead acid lithium batteries have the diaphragm, diaphragm has resistance, such as lithium valve-control sealed lead-acid battery there are generally two types: the superfine glass fiber mat ( AGM) For the diaphragm, the other is colloid electrolyte used PE or other plastic plate. AGM as lithium valve-control sealed lead-acid battery diaphragm, internal resistance affected by assembly of the compression ratio, generally valve-control sealed lead acid lithium battery is lower than ordinary battery internal resistance. In the composition of AGM separator resistance affected by the following factors. The electrolyte saturation when the suction fluid saturation of 80% - in the AGM 100%, its lowest battery internal resistance. As the saturation to reduce 60% 80 im, battery internal resistance obviously increases, when the saturation below 60%, battery internal resistance to further increase. AGM in electrolyte of saturation due to the depth of discharge, one-way valve set pressure, seal leakage, etc. Such as open the valve set pressure is too low, easy open valves, valve 'frequent, discharge depth is very big, there are some seal leakage, etc. , this will accelerate water loss, AGM in desaturation, diaphragm resistance is increased. b。 The height of AGM when the battery is too big, due to the core in the AGM absorption effect, dilute the thick on electrolyte distribution appears phenomenon, namely concentration layer phenomenon. In addition, discharge cause uneven distribution of the electrolyte. c。 AGM thickness can be changed after the AGM thickness and porosity, but the total surface area will increase, therefore the resistance smaller. After all, in the process of charging and discharging, AGM compression ratio will change, there are differences between the pressure of the condition of a AGM, resistance is not evenly distributed, the battery internal resistance will also change. (2) battery assembly process of the assembly, a group of welding, a column of material and cross section, a column and the welding quality of busbar can affect battery internal resistance, so you must determine the assembly process is in place, so as to reduce the contact resistance of the battery, Ohmic resistance) 。 (3) working current in the discharge process, the plate active substances by electrical conductivity good PbO2 and Pb will generate electrical conductivity poor PbSO4, make active material resistance increases. Since PbSO4 layer porosity of active material decreases, H + in the sulfuric acid electrolyte decreases and the SO 42 - Spear plate internal diffusion velocity, thus increasing the concentration polarization; Layer and reduce the active material and sulfuric acid reaction area, thus increasing the electrochemical polarization. Because of the concentration polarization and electrochemical polarization results form the polarization resistance. And sulfuric acid concentration is more and more thin, with the increase of the depth of discharge make battery ohm resistance increases. When the discharge current increases, the poles in the battery PbSO4 layer thickening rapidly, battery internal resistance increases significantly. After discharge the battery resistance high 2 - than when fully charged Three times that of valve-control sealed battery internal resistance is lower than ordinary rich liquid type of battery internal resistance.