改善电动汽车性能的电池平衡技术。第二部分：主动平衡技术

　　改善电动汽车性能的电池平衡技术。第二部分：主动平衡技术

　　平衡电池单体充放电特性的技术对于延长电动汽车和许多便携式电子产品的使用范围和使用寿命至关重要。事实上，无源电池平衡的讨论在本系列的第一部分已经在使用的大多数今天的混合动力和插电式混合动力车5 kwh-20千瓦时电池管理系统保护部分技术（PHEV）。这些“聪明”的被动平衡系统使用阻抗跟踪、库仑计数和其他状态监测技术（图1）。

　　Figure 1： Battery management plays a critical role in modern EV propulsion systems. （Courtesy of Maxim Integrated Circuits）。

　　Since even these advanced passive balancing systems allow cells with higher capacity to fully charge by repeatedly bleeding off the energy in weaker cells， they can only unlock a portion of a battery’s “stranded” capacity. As a result， there is a lively debate about whether the next generation of pure EVs can tolerate the lost range and lost charge/discharge cycles if their 25-100 kWh batteries are passively balanced.

　　At least in theory， the better alternative is an active cell balancing system which re-distributes the charge from stronger cells to prop up the weaker cells within a battery stack. But， while electronics manufacturers are promoting the virtues of their early active cell balancing technologies， many battery and electric vehicle manufacturers have concerns about whether active systems’ added cost and complexity are worth the extended range and operational lifetime they provide.

　　In this article， we will take a closer look at active cell balancing techniques and where they may play a role in the next generation of electric vehicles and other high-capacity storage applications.