電池組需用到大量的電池來組成，但同型號的電池各自還是有著不同的特性如自放率、內阻與溫度等，都會有些許差異而導致電池之間容量或電壓不平均，進而影響電池組充放電的效率不佳，無法有效的利用電池組的電量，為了解決此問題，需要透過電池平衡器來使電池組之間保持平衡。
本文所研製之四組雙向直流轉直流降/升壓轉換器，當容量差異過大時會啟動平衡機制，根據電池狀態，在放電時分配負載功率來延長系統使用時間，充電時分配充電電流使充電結束時各個電池皆達滿電狀態，藉此在充放電過程中皆能完成平衡。然而，平衡係數若採累加制進行運算，容易會有平衡後期平衡速度下降的問題，為了加快平衡速度，本論文對此方法進行改善並透過調整輸出電壓範圍、責任週期變動量範圍和平衡係數的計算方式來使平衡速度加快。
在放電模式下，根據輸出電壓範圍和平衡係數的計算方式不同分為三組平衡實驗和一組無平衡實驗，共四組實驗。輸出電壓範圍不同時，所提技術可節省25.7%時間，加上改善控制法後可節省32%的時間，相較於無平衡實驗放電時間都延長17%左右。在充電模式時，本文考量兩種情境，情境一為低容量情境，總共四組實驗，根據責任週期變動量範圍和平衡係數的計算方式的不同分為三組平衡實驗和一組無平衡實驗。平衡係數的計算方式不同時，所提方法可節省17.8 %的時間，加上調整責任週期變動量範圍技術後可節省29.9 %的時間 情境二為中高容量情境，驗證當其中一顆電池電壓達到4.2 V仍可繼續保持平衡，且充電結束時容量差小於1%。

The battery pack requires a large number of batteries to be assembled. But the batteries of the same model still exhibit slight differences in characteristics such as self-discharge rate, internal resistance, and temperature, differ slightly, resulting in uneven capacity or voltage distribution. This imbalance affects the efficiency of battery charging and discharging, preventing the effective utilization of the battery pack's capacity. To address this issue, a battery balancer is required to maintain balance among the batteries in the pack.
In this study, four sets of bidirectional buck-boost DC-DC converters were developed. When the capacity difference exceeds a certain threshold, the balancing mechanism is activated. Based on the battery states, the load power is distributed during discharge to extend the system's usage time, and the charging current is distributed during charging to ensure that all batteries reach full charge by the end of the charging process. This ensures balance throughout the charging and discharging cycles. However, if the balancing coefficient is calculated using cumulative summation, there is a potential issue of decreasing balance speed in the later stages. To accelerate the balancing process, improvements were made to this method by adjusting the output voltage range, duty cycle variation range, and calculation method of the balancing coefficient.
In the discharge mode, the experiments were divided into three experiments with balancer and one experiment without balancer. The proposed technique saved 25.7 % of the time in different output voltage range scenarios. With the improved control method, the time savings increased to 32%. Compared to the results obtained without balancer, an extension of discharge time by approximately 17% can be achieved. In the charging mode, two scenarios were considered. Scenario 1 involved low-capacity situations, with a total of four experiments. The experiments were also divided into three experiments with balancer and one experiment without balancer The proposed method saved 17.8 % of the time in different balancing coefficient scenarios. With the adjustment of the duty cycle variation range, the time savings increased to 29.9%. Scenario 2 involved medium to high capacity situations, the obtained results verify that the balancing could be maintained even when one battery reached 4.2 V, and the capacity difference at the end of charging was less than 1%.

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