時間常數比對之電池健康狀態判定系統

Abstract

在電動車系統當中，瞭解電池的State-of-Health(SOH)是很重要的一件事。本論文提出以時間常數比對之電池SOH判定系統，以電池時間常數作為老化指標，選用此參數作為老化指標是因為電池的時間常數代表著的是電池充放電時的電池端電壓反應速度以及電池內部化學反應的變化，且經由實驗的結果證明老化效應確實會造成電池時間常數的上升，而本論文採用的電池SOH判定法是以老化電池與新電池時間常數的比例關係建立SOH預測線，藉此免除對不同電池需要建立不同模型的限制，並且以此判定法解決傳統SOH判定法所存在的問題，而目前最廣泛使用的SOH判定法主要有兩種，第一種判定法是利用電池滿電位電量(Full-Charge-Capacity, FCC)做為電池SOH的判定基準，此方法的判定指標FCC值需要經過長時間的充放電測試，因此無法對電池做一個快速檢測；第二種判定法是利用量測電池的內阻抗值決定電池SOH，但是此方法會受到環境阻抗的影響而造成SOH判定上很大的誤差。本論文所提出的時間常數比對之電池SOH判定系統，藉由電池時間常數此不同於傳統SOH判定法的嶄新老化指標，只需要對電池做短時間的充電測試，就能夠達到不受環境阻抗影響且能夠快速檢測電池SOH的系統，量測時間為以1C充放電測試下FCC判定法的0.14%，且利用一個新電池以及一個老化過後電池做基準所實作的成果可以達到平均誤差在1%以下、最大誤差在2%以下的準確度。

The SOH of batteries is critical information for electric vehicle (EV) and hybrid electric vehicle (HEV) systems. This thesis proposes an SOH estimation system based on time-constant-ratio measurement. The reasons of using time-constant as a criterion of aging effect is because that time-constant not only represents the response speed of terminal voltage during charging and discharging but also represents the change of internal chemical reactions. The experimental results show that aging effect will increase time-constant. Furthermore, the use of time-constant-ratio for estimating SOH can build the SOH predicting line by the time-constant-ratio of new cell and aged cell in which does not need to rebuild model for different kind of batteries. The proposed estimation is thus able to resolve the issues of traditional SOH estimations. There are two widely used battery SOH estimations. The first one is using the battery’s full-charge-capacity (FCC) as standard of battery SOH. Unfortunately, to access FCC information need to take a long-term charging and discharging test. Therefore, FCC estimation fails to be a fast SOH estimation. The second estimation is using the battery impedance as standard of SOH. However, this SOH estimation may cause large error due to the effect of environmental impedance. For improving the above issues on different SOH estimations, this thesis proposes an SOH estimation system based on time-constant-ratio measurement. The time-constant-ratio is a novel criterion for testing aging effect. The use of this novel criterion for SOH estimation helps to achieve the purpose of an environmental-impedance-free and fast SOH estimation. The proposed estimation is 0.14% the measured time of FCC estimation based on 1C charging and discharging. The measured results have average error below 1% and maximum error below 2% by using a new battery and an aging battery to build the predicting line of SOH.