Why does the battery capacity of electric vehicles drop?

Many users will feel that the capacity of the battery seems to be getting less and less and the riding distance is getting shorter and shorter during the use of the battery of the electric vehicle. What is the reason for the decrease in battery capacity of electric vehicles? In addition to the factors of the battery itself, it is also related to your daily usage habits and the working environment of electric vehicle batteries. The following author will carefully explain the reasons for the decrease in battery capacity of electric vehicles.　　1. Sulfation 　　In the use of electric vehicle batteries, over-discharge or untimely charging after discharge will cause lead sulfate to recrystallize. The recrystallized lead sulfate is dense and coarse. If it is not charged, it will be difficult to completely reduce it. This incompletely reduced lead sulfate crystallization will reduce the discharge capacity, making it easier for electric vehicle batteries to over-discharge, thereby producing more denser and coarser recrystallizations. Such cycles will cause premature aging of electric vehicle battery capacity. 2. Passivation Passivation is mainly manifested on the positive electrode. The float voltage after deep discharge is too low or the overcharge is more than 120% after multiple cycles will increase the thickness of the barrier layer, increase the resistance of the barrier layer, and finally appear constant. The voltage charging current is small, and the voltage at the constant current charging terminal rises quickly, and it cannot be fully charged under normal conditions. The terminal voltage drops rapidly during discharge, making the discharge capacity much lower than the design capacity value, and premature battery capacity deterioration occurs. 3. The formation of the barrier layer. The battery works in a deep cycle charge and discharge environment for a long time. If the grid alloy and the active material are not well combined, the expansion of the active material in each cycle will shrink the electric vehicle battery, which will cause the grid to interact with each other. The bonding surface of the active material forms a corrosive layer during floating charging. This corrosive layer can be a conductor or a poor conductor depending on the alloy composition used. If it is a poor conductor, it will quickly deteriorate the charge and discharge performance of the battery and cause premature deterioration of the electric vehicle battery capacity.　　To sum up, there are many reasons for the decrease in battery capacity of electric vehicles. We must take corrective measures to extend the life of the battery. Previous: Precautions for maintenance of electric vehicle batteries in winter