Consistency issues with lithium batteries

Consistency issues with lithium batteries

Lithium batteries cannot be made into a large one, so we have to organize numerous small cells together. With everyone working together and sincere cooperation, we can also take electric vehicles flying. At this point, we need to face a problem of consistency.

Our daily experience is that when two dry batteries are connected with their positive and negative electrodes, a flashlight can emit light. Who cares if it is consistent or not. However, the large-scale application of lithium batteries is not so simple.

The inconsistency of lithium battery parameters mainly refers to the inconsistency of capacity, internal resistance, and open circuit voltage. Using inconsistent battery cell strings together can result in the following issues.

1) Capacity loss occurs when individual cells form a battery pack, and the capacity follows the “bucket principle”. The capacity of the worst cell determines the overall capacity of the battery pack.

In order to prevent overcharging and overdischarging of the battery, the logic of the battery management system is set as follows: during discharge, when the lowest cell voltage reaches the discharge cut-off voltage, the entire battery pack stops discharging; When charging, stop charging when the highest cell voltage reaches the charging cut-off voltage.