The inconsistency of the battery is important in the manufacturing process, due to the technological level of the battery plate thickness, the microporosity rate, the activation degree of the active substances exist slight differences. The inconsistency in the internal structure of the battery will make it impossible for the voltage, capacity and internal resistance of the same type of battery delivered from the same batch to be completely consistent. The influence of single battery inconsistency on the service life of power lithium battery pack is divided into voltage inconsistency, capacity inconsistency and internal resistance inconsistency.

In the process of single battery group, if the voltage inconsistency is large, the low-voltage battery and the normal battery will become the load of the battery group. Because when there is a low voltage battery in two parallel batteries, the phenomenon of mutual charging will occur, and other batteries will charge the battery. This connection mode will increase the capacity of low-voltage battery to a small extent and reduce the capacity of high-voltage battery to a large extent, and the energy loss in mutual charging can not reach the ideal external output.

The inconsistency of initial capacity has been greatly reduced by screening before battery grouping. In the process of use, although the difference of initial capacity of individual batteries can be balanced by charging individual batteries separately. However, the continuous charging and discharging cycle of electric vehicles magnifies this inconsistency to some extent. The capacity decays at different rates along with the cycle. With the increase of battery cycles, the capacity difference will become larger and larger. In this way, the capacity of a single battery deteriorates and degrades the capacity of the whole battery pack.

Due to the inconsistency of the internal resistance, the voltage and current distribution of a single battery in the battery string is uneven, and overvoltage charge or undervoltage discharge occurs in some parts. The inconsistency of internal resistance also causes the heat loss of a single battery in the discharge process. The larger the internal resistance is, the faster the temperature will rise, which may eventually lead to thermal runaway.

Inconsistencies such as voltage, capacity, and internal resistance lead to differences in battery life and battery pack life, which are mainly reflected in differences in temperature, charge-discharge ratio, discharge depth, and available capacity. For example, due to the difference in discharge depth, most of the batteries are in shallow discharge state, while the batteries with low capacity are in deep discharge state.