The measuring methods for lithium ion battery capacity are basically the same as those for battery discharge performance, including constant current discharge, constant resistance discharge, constant voltage discharge, constant voltage discharge, constant current discharge, continuous discharge and intermittent discharge.

Constant current method circuit: The advantage of this method is that the current is stable during discharge, so its capacity can be easily calculated. The discharge capacity of the constant current method has a great relationship with the discharge current, and the discharge system, charging system, shelving time, etc. will affect the capacity. Under the same discharge system, different charging systems have different charging efficiency for the battery, so the discharge capacity of the battery will also be different.

In the discharge process of measuring capacity by constant resistance method, the discharge current is not a fixed value, the discharge current is large at the beginning and then gradually decreases, and the larger the discharge electric shock is, the smaller the discharge current is, the smaller the voltage drop appears, the working voltage drops slowly, the discharge curve is flat, and the discharge capacity is larger.

Batteries of different types and with different degrees of freshness cannot be mixed to avoid over charging and over discharging due to mismatched battery capacity. In the battery pack, its overall performance is generally determined by the battery with the worst performance. As for the primary battery, the capacity test is destructive, so the product consistency can only be maintained through strict production control.

With the further expansion of the electric vehicle market and the continuous improvement of the requirements for the endurance mileage, vehicle companies have put forward higher requirements for power lithium batteries in terms of energy density, manufacturing cost, cycle life and additional attributes of products. On the premise of no great breakthrough in the field of raw materials, appropriately increasing the volume of the battery to obtain more battery capacity will become a direction that can be explored.