What are the causes of problems with electric vehicle batteries?

Causes of problems in electric vehicle batteries 1.1 Why do you say that caused by the battery itself? We know the working principle of lead-acid batteries. The process of charging and discharging lead-acid batteries is the process of electrochemical reaction. When charging, lead sulfate forms lead oxide and discharges. When the lead oxide is reduced to lead sulfate. Lead sulfate is a substance that is very easy to crystallize. When the concentration of lead sulfate in the electrolytic solution of the battery is too high or the static idle time is too long, it will clump together and form small crystals. These small crystals attract the surrounding sulfuric acid. Lead, like a snowball, forms large inert crystals. The crystallized lead sulfate can no longer be reduced to lead oxide when it is charged, but it also precipitates and adheres to the electrode plate, causing the working area of u200bu200bthe electrode plate to decrease. This phenomenon is called vulcanization. At this time, the battery capacity will gradually decrease until it becomes unusable. When a large amount of lead sulfate is piled up, it will attract lead particles to form lead branches, and the lead branches between the positive and negative plates will cause short circuit of the battery. If there are gaps on the surface of the electrode plate or the sealed plastic case, lead sulfate crystals will accumulate in these gaps, and expansion tension will appear, which will eventually cause the electrode plate to break off or the shell to break, causing irreparable physical damage to the battery. Therefore, an important mechanism leading to lead-acid battery failure and damage is that the battery itself cannot prevent vulcanization. 1.2 Reasons for battery processing In view of the particularity of lead-acid batteries for electric bicycles, various battery manufacturers have adopted a variety of methods. The most typical method is as follows: ①Add the number of plates. The original design of a single grid of 5 pieces and 6 pieces was changed to 6 pieces and 7 pieces, 7 pieces and 8 pieces, or even 8 pieces and 9 pieces. By reducing the thickness of the electrode plates and separators, and increasing the number of electrode plates, the battery capacity can be increased. ②Increase the specific gravity of sulfuric acid in the battery. The sulfuric acid specific gravity of the original floating battery is generally between 1.21 and 1.28, while the sulfuric acid specific gravity of the battery of the electric bicycle is generally between 1.36 and 1.38, which can supply a larger current and increase the initial capacity of the battery. ③The amount and proportion of lead oxide, which is the active material of the new positive plate The addition of lead oxide increases the electrochemical reaction substances involved in the discharge, which also increases the discharge time and the battery capacity. Through these measures, the initial capacity of the battery meets the capacity requirements of the electric bicycle, and in particular, the high-current discharge characteristics of the battery are improved. However, with the addition of the plates, the capacity of sulfuric acid is reduced, and the battery heats up to cause a large amount of water loss. At the same time, the probability of the battery's micro-short circuit and lead bridging has increased. Increasing the sulfuric acid ratio re-increased the initial capacity of the battery, but the vulcanization phenomenon became more serious. One of the most basic principles of sealed batteries is that after oxygen evolution from the positive plate, the oxygen goes directly to the negative plate, where it is absorbed by the negative plate and reduced to water. The parameter for evaluating the technical index of the battery is called the sealing reaction efficiency. This phenomenon is called oxygen circulation. In this way, the battery loses little water, and the maintenance-free is realized, that is, no water is added. For this reason, the capacity of the negative plate is required to be larger than that of the positive plate, which is also called negative transition. The addition of active material on the positive plate will inevitably reduce the transition of the negative electrode, worsen the oxygen cycle, increase the loss of water, and cause vulcanization. Although these measures have increased the initial capacity of the battery, they will cause loss of water and vulcanization, and the loss of water and vulcanization will contribute to each other, and the final result is to sacrifice the life of the battery. Disclaimer: Some pictures and contents of articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous article: What are the corresponding protection measures for lithium batteries?