As discussed previously, battery systems, in particular Li-Ion systems, require some form of electronic battery management to ensure safe, reliable, and efficient operation. The basic functions needed are the precise control of charge current and voltage, prevention of abuse conditions, and monitoring the capacity level of the battery. Additionally, “smart” battery systems will communicate important information about  the battery capacity, health, and status to the host system for display to the user. While there are many variations of pack configurations and capacities for different applications, the basic functions of battery management circuitry are roughly the same. However smaller packs generally have simpler circuitry, while larger applications like electric vehicles can have very complex designs owing to the larger packs with many cells and higher load current levels.