What are the balancing technologies for lithium batteries?

The important issue in the production of lithium batteries is the use of batteries in groups. In order to deal with battery consistency issues, the industry generally uses equalization techniques. At present, the industry divides mainstream battery equalization techniques into passive equalization, active equalization, and internal equalization. 1. Commonly used equalization methods include active equalization method and passive equalization method realized by circuit. The passive equalization method is to discharge a single battery with a high voltage through a circuit through a load resistor, and judge whether its voltage is the same as the voltage of other single batteries through a comparison circuit, and stop discharging if it is the same, and passively balance The disadvantage of the method is that the energy of the single battery is consumed, heat is generated, and the equilibrium time is long. The characteristic of the passive equalization method is that the principle is simple and easy to implement. When the equalization current is small, the cost of the device is relatively low, but there are two major problems: ①Resistor can consume discharge, waste energy, and generate heat; ②It is impossible to choose the discharge resistance Too small, at the end of the charge, the voltage of the small-capacity battery is often higher according to the battery characteristics. In the static equilibrium, the power of the small-capacity battery is discharged, which increases the mutual difference between the batteries. 2. The active equalization method means that the energy of the battery with higher voltage is not consumed through the resistance during charging and discharging, but the energy is transferred to the battery with lower voltage, so as to realize the balanced charging and discharging of the lithium battery pack; active equalization circuit It is complicated, cannot balance all batteries at the same time, and reliability needs to be improved. The key features of the active equalization method are the use of DC/CD bidirectional active equalization circuit, high equalization efficiency, equalization during charging, discharging and static process, large balance current, faster equalization speed, but there are two major problems: ①Technology Complex, high cost, and difficult to implement; ② Frequent switching of equalization circuits can cause great damage to the battery and affect the life of the battery. 3. The internal equalization method uses BMS to adjust the charging current and control the topological algorithm of the charging voltage in the process of charging the battery in series, so that the charge of each single battery in the battery pack is basically the same. The characteristics of internal equalization technology are simple algorithm, no energy loss, no additional charge and discharge process, no impact on battery life, no new hardware equipment, but if the battery charge varies greatly, it will take a longer time to balanced. The inconsistency of the battery comes from the internal resistance, capacity and SOC of the battery, and the traditional consistency evaluation method and the voltage consistency other than the equalization method are used as the control target, which does not effectively increase the available capacity of the battery pack, so it cannot improve the consistency of the battery pack. The problem has an adverse effect on the use of battery packs. Since the DC internal resistance, polarization voltage, and maximum usable capacity are specific parameters of the battery, there is basically no change during one or several successive charging and discharging processes, so the balance of the battery pack must be achieved by adjusting the SOC of each single battery. . After research, the SOC is used as the reference object of balance, the balance object is relatively fixed, the balance time is fully utilized, the balance utilization rate is improved, and the balance current capacity is reduced. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous: Issues affecting the life of lead-acid batteries and solutions