Well written and worth the read, thanks again to HKtech @ Ioniq5 forum
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High-voltage (HV) DC packs are the heart of electric vehicles (EVs), storing the electrical energy that powers the motor. However, a key challenge in maximizing an HV DC pack's performance is internal resistance. Here's a breakdown of how internal resistance affects efficiency.
Internal Resistance:
All electrical conductors, including the cells within an HV DC pack, exhibit some degree of internal resistance (Rint). This resistance opposes the flow of current through the pack.
Impact on Efficiency:
During discharge (powering the motor), internal resistance creates a voltage drop (ΔV) across the pack, following Ohm's Law (ΔV = Rint * I, where I is the discharge current). This voltage drop represents lost energy, dissipated as heat within the pack.
Higher internal resistance leads to a greater voltage drop and consequently, lower efficiency. The pack delivers less usable energy to the motor, reducing the vehicle's driving range.
During charging, internal resistance also causes a voltage drop, leading to increased energy losses and longer charging times.
Factors Affecting Internal Resistance:
Cell Chemistry: Different battery cell chemistries have varying inherent resistances. Lithium-ion (Li-ion) cells commonly used in EVs typically have lower internal resistance compared to older technologies.
Cell Temperature: Internal resistance generally increases with higher cell temperatures. Thermal management systems are crucial for maintaining optimal cell temperature and minimizing resistance.
Cell Age and Degradation: Over time, battery cells can experience degradation, leading to increased internal resistance. This can contribute to reduced pack capacity and efficiency as the vehicle ages.
Strategies to Mitigate Internal Resistance:
Cell Selection: Choosing battery cells with inherently low internal resistance is a primary strategy. Advancements in cell technology are continuously pushing the boundaries of lower resistance.
Pack Design: Optimizing the pack design, including cell arrangement and current collectors, can minimize internal resistance. Techniques like parallel connections can reduce the overall effective resistance of the pack.
Battery Management System (BMS): A sophisticated BMS continuously monitors cell voltages and temperatures. By adjusting charging and discharge currents, the BMS can help mitigate the effects of internal resistance and optimize overall pack health.
Conclusion:
Internal resistance is an inevitable factor in HV DC packs. However, by understanding its impact on efficiency and employing strategies like cell selection, pack design optimization, and effective BMS management, engineers can minimize its effects and ensure the optimal performance of EVs.
:High-voltage (HV) DC packs are the heart of electric vehicles (EVs), storing the electrical energy that powers the motor. However, a key challenge in maximizing an HV DC pack's performance is internal resistance. Here's a breakdown of how internal resistance affects efficiency.
Internal Resistance:
All electrical conductors, including the cells within an HV DC pack, exhibit some degree of internal resistance (Rint). This resistance opposes the flow of current through the pack.
Impact on Efficiency:
During discharge (powering the motor), internal resistance creates a voltage drop (ΔV) across the pack, following Ohm's Law (ΔV = Rint * I, where I is the discharge current). This voltage drop represents lost energy, dissipated as heat within the pack.
Higher internal resistance leads to a greater voltage drop and consequently, lower efficiency. The pack delivers less usable energy to the motor, reducing the vehicle's driving range.
During charging, internal resistance also causes a voltage drop, leading to increased energy losses and longer charging times.
Factors Affecting Internal Resistance:
Cell Chemistry: Different battery cell chemistries have varying inherent resistances. Lithium-ion (Li-ion) cells commonly used in EVs typically have lower internal resistance compared to older technologies.
Cell Temperature: Internal resistance generally increases with higher cell temperatures. Thermal management systems are crucial for maintaining optimal cell temperature and minimizing resistance.
Cell Age and Degradation: Over time, battery cells can experience degradation, leading to increased internal resistance. This can contribute to reduced pack capacity and efficiency as the vehicle ages.
Strategies to Mitigate Internal Resistance:
Cell Selection: Choosing battery cells with inherently low internal resistance is a primary strategy. Advancements in cell technology are continuously pushing the boundaries of lower resistance.
Pack Design: Optimizing the pack design, including cell arrangement and current collectors, can minimize internal resistance. Techniques like parallel connections can reduce the overall effective resistance of the pack.
Battery Management System (BMS): A sophisticated BMS continuously monitors cell voltages and temperatures. By adjusting charging and discharge currents, the BMS can help mitigate the effects of internal resistance and optimize overall pack health.
Conclusion:
Internal resistance is an inevitable factor in HV DC packs. However, by understanding its impact on efficiency and employing strategies like cell selection, pack design optimization, and effective BMS management, engineers can minimize its effects and ensure the optimal performance of EVs.