Introduction:
Last weekend, I embarked on an exciting road trip with my Solterra electric vehicle (EV). Throughout the journey, I kept a close eye on the charging process and collected valuable data to better understand the charging characteristics of my EV. In this blog post, I'll share my observations and present a charging curve chart that represents the estimated charging behavior of my Solterra. Additionally, I'll discuss some limitations I encountered during the constant voltage phase and my hypothesis of "cool gating." Let's delve into the details!
Understanding the Charging Curve:
To analyze the charging behavior of my Solterra, I constructed a charging curve chart based on my road trip data. The chart showcases the relationship between the state of charge (SoC) and battery charging power (y-axis). The orange line represents the charging curve under ideal conditions, assuming an optimal temperature range and a charging station capable of supplying the required current.
Ideal Charging Curve:
According to the ideal charging curve, the charging process follows three primary phases. Initially, the constant current (CC) phase allows for rapid charging, maintaining a steady charging current until reaching approximately 17% SoC. Subsequently, the constant voltage (CV) phase begins, during which the charging voltage remains constant, and the charging current gradually declines. This phase continues until approximately 47% SoC. Finally, the taper charging phase initiates, where the charging rate significantly slows down as the battery nears its maximum capacity.
Yellow Line: Cool Gating:
During my first charges of the day, I noticed a limitation in the charging process, specifically during the constant voltage phase. To represent this limitation on the chart, I plotted a yellow line, suggesting the occurrence of "cool gating." Although further data is needed to confirm this hypothesis, I suspect that battery temperature might be a contributing factor. "Cool gating" appears to restrict the charging speed during the constant voltage phase, potentially as a protective measure for the battery. I plan to gather more data to gain a deeper understanding of this phenomenon.
Gray Line: Two-per-Day DC Fast Charge Limit:
On my road trip, I encountered a charging limit twice, indicated by the gray line on the chart. This limitation seemed to come into effect when the state of charge was above 40%. However, it's important to note that Toyota is actively addressing this limitation. In a recent software release that is currently being distributed, Toyota plans to increase the two-per-day DC fast charge limit to approximately four per day. This update will provide Solterra owners with greater flexibility and convenience during their charging sessions.
Future Blog Posts:
In the coming blog posts, I will share detailed charging session data, overlaying the actual charging sessions onto the charging curve chart. By doing so, I hope to present a comprehensive analysis of my Solterra's charging behavior and shed light on the real-world charging experiences encountered during my road trip.
Contributing to the Knowledge Base:
For fellow Solterra or bZ4X owners interested in collecting charging data with Torque Pro, I am offering instructions and the necessary PIDs (parameter IDs) to aid in building a collective knowledge base for this family of vehicles. By collaboratively collecting and analyzing charging data, we can enhance our understanding of the Solterra's charging characteristics and help optimize the EV ownership experience.
Conclusion:
My recent road trip with the Solterra provided valuable insights into the charging characteristics of my EV. By plotting a charging curve chart and identifying limitations such as "cool gating" and the two-per-day DC fast charge limit, I am gaining a deeper understanding of how my Solterra charges under different conditions.
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