改善電動汽車性能的電池平衡技術。第二部分：主動平衡技術

　　平衡電池單體充放電特性的技術對于延長電動汽車和許多便攜式電子產品的使用范圍和使用壽命至關重要。事實上，無源電池平衡的討論在本系列的第一部分已經在使用的大多數今天的混合動力和插電式混合動力車5 kwh-20千瓦時電池管理系統保護部分技術（PHEV）。這些“聰明”的被動平衡系統使用阻抗跟蹤、庫侖計數和其他狀態監測技術（圖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.