Lithium battery capacity, measurable capacity, is the maximum amount of electricity that can be charged and discharged within a reasonable maximum and minimum voltage range of the battery. Before being mounted on the vehicle, the capacity of the unit can be measured by charging and discharging. Once in the car, the battery capacity can only be estimated by algorithms. In the battery management system BMS, accurately estimating the battery state of charge SOC is an important indicator of its design level.

　The current well-known practice is to integrate the loop current ampere-hour integration under dynamic working conditions, and to check the battery power with the battery open circuit voltage in the non-working state. Although there are many other methods, they are either poorly stable or overly computationally intensive, and are rarely used in batches.

　　The capacity of the monomer is obviously affected by the degree of aging. Everyone knows that when the capacity decays to a limit value when the battery is eliminated, it can be seen that the two have an absolute correlation. Secondly, the capacity is also affected by temperature. At low temperatures, the activity of the active material decreases and the number of ions that can be provided decreases, and the capacity will inevitably decrease.