Lithium-ion battery charger charging technology
3.1 Status and development trend
In practical applications, selecting different charger charging modes according to battery capacity limits is an inevitable choice to extend battery life. Lithium-ion battery chargers have more charging methods, the simplest is the constant voltage charger charging method. Lithium-ion battery packs generally consist of a large number of monomers connected in series. Due to the difference in manufacturing process of each monomer, there are inconsistencies in internal resistance, voltage, capacity and temperature, which may cause imbalance in the process of charging and discharging, that is, large-capacity singles. The body is shallow and the small capacity unit is over-discharged, which will cause serious damage to the battery pack. Solving the problem of unbalanced charging and discharging is the research focus of lithium-ion battery packs.
The requirements for electric vehicle charging technology for battery chargers include:
(1) The charger charging process is fast. The low power ratio of the power battery leads to a short cruising range of the one-time charger, which has been an important factor limiting the development of electric vehicles. As long as the battery is charged faster and more efficiently, it can indirectly compensate for the weakness of the short range of electric vehicles.
(2) The charging device of the charger is generalized. In order to pursue relevant academic frontiers and optimize their products to gain as much market share as possible, various new types of batteries have emerged in an endless stream and coexist in this market. In the case where batteries of different types and different voltage levels coexist, the charging device of the charger in the public place needs to have wider adaptability. On the one hand, the charger of the charger needs to be applied to as many batteries as possible, and on the other hand, for different batteries. Voltage level, charger chargers need to meet customer requirements.
(3) The charger charging strategy is intelligent. In order to realize the charging of the non-destructive charger of the battery as much as possible, monitor its charging and discharging state, avoid over-discharging, achieve the purpose of energy saving and delay aging, and need a smarter charging strategy of the charger. That is, different charger charging strategies are provided for different batteries to match the battery charger charging curve.
(4) Efficient power conversion. The energy loss of electric vehicles is closely related to the operating cost. In order to further promote electric vehicles, it is necessary to balance their cost performance and reduce energy consumption.
(5) The charger charging system is integrated. With the requirements of system miniaturization and multi-functionality, as well as the improvement of battery reliability and stability requirements, the charger charging system will be integrated with the electric vehicle energy management system as a whole, integrating current detection and reverse discharge protection. A smaller, more integrated charger charging solution can be realized without external components, saving space for the rest of the electric vehicle, greatly reducing system cost, optimizing charger charging and extending battery life.
3.2 smart charger charging technology
Based on the above analysis of the current status of charging lithium-ion battery packs and their chargers, this paper summarizes an intelligent charger based on electric vehicle BMS for the imbalance and safety problems in the charging process of lithium-ion battery pack chargers. Charging mode
During the charging process of the charger, the BMS system mainly monitors the voltage and current signals of the lithium-ion battery pack, and detects the temperature and connection status. The intelligent management system in the charger of the charger is for the output mode of the charging device of the charger. Real-time monitoring. The BMS system and the charging device charging device intelligent management system realize intelligent communication, perform real-time mode comparison between the battery pack and the charging device charging device state, and select an optimal charging mode for the battery pack.
During the initial charging process of the charger, the BMS allows the maximum charge of the lithium ion battery pack to be estimated, that is, the SOC of the entire battery pack is evaluated, and the maximum chargeable capacity of the battery pack is measured. Combined with the preset safety factor of the charging capacity of the charger, the maximum allowable charging capacity of the battery pack is calculated.
During the charging process of the charger, the lithium ion battery pack is charged by the charger according to the maximum allowable charger charging amount. Make full use of the BMS energy management module to perform charge equalization control on the battery pack unit to ensure the consistency of the single parameters. At the same time, during the charging process of the charger, it is necessary to periodically check the SOC value (the detection period is determined according to the increasing gradient of the battery charge).
Utilize the state estimation function of the BMS system, combined with safety management, to minimize the charging of the battery pack's overcharger. After reaching the maximum charge of the battery pack, both the BMS and the charger charging device intelligent management system can intelligently control the charger charging controller to end the charging process of the charger. At the same time, the BMS disconnects communication with the charger's intelligent monitoring system.
The charging method of the intelligent charger can not only solve the problem of unbalanced charging of the lithium ion battery pack charger, but also ensure the charging safety of the battery pack charger to the utmost extent, prolong the service life of the lithium ion battery pack, and ensure the safety of use thereof.