1 Voltage grouping method Voltage grouping method can be divided into static voltage grouping method and dynamic voltage grouping method. The static voltage matching method is also called no-load matching method. With no load, only the battery itself is considered. It measures the self discharge rate of the screened single battery stored in full charge state after being left for tens of days and the open circuit voltage of the battery in different storage periods under full charge state. This method is the simplest but not accurate. The dynamic voltage matching method is not accurate because it does not take into account the load change and other factors.

2 Static capacity matching method: charge and discharge the battery under the set conditions, calculate the capacity according to the discharge current and discharge time, and group the battery according to the capacity. This method is simple and easy to operate, but it can only reflect that the capacity of the battery is the same under specific conditions, and cannot explain the complete working characteristics of the battery, so it has certain limitations.

3 The internal resistance matching method mainly considers the internal resistance of the single battery. This method can achieve rapid measurement, but because the internal resistance of the battery will change with the discharge process, it is difficult to accurately measure the internal resistance.

4 The multi parameter matching method considers the capacity, internal resistance, voltage, self discharge rate and other external conditions to comprehensively evaluate the battery, and can select the battery pack with good consistency. But the premise of this method is that the single parameter sorting should be accurate and time-consuming.

5 Dynamic characteristic matching method Dynamic characteristic matching method is to use the charge discharge characteristic curve of the battery to select the battery for matching. The charge discharge curve can reflect most characteristics of the battery, and the dynamic characteristics matching method can ensure the consistency of various performance indicators of the battery. The dynamic characteristic matching method has many data, which is usually realized by computer program. In addition, this method reduces the utilization rate of the battery pack, which is not conducive to the reduction of the cost of the battery pack. The determination of standard curve or datum curve is also a difficult point in its implementation.