Batteries are the heartbeat of electric vehicles (EVs), especially in the heavy-duty commercial sector. They power everything from delivery trucks to port equipment, enduring extreme conditions while maintaining safety and performance. To meet these challenges, Proterra batteries undergo a rigorous series of tests that evaluate everything from their protective enclosures to the cells inside. This comprehensive testing approach ensures that our batteries can handle the demands of real-world applications, providing the reliability and longevity that commercial vehicles and industrial equipment require. 

Ingress Protection Testing 

Ingress protection is crucial for defending the battery against external elements like dust, moisture, and water. In most applications, batteries are often exposed to challenging conditions, such as torrential rain, rough terrain, dusty construction sites, and muddy off-road environments. Ensuring that our batteries are shielded from these elements is vital for their performance. 

The enclosure is the protective outer shell of our battery pack. It serves not only as a cover but also as a defensive shield for the internal components and providing structural support. This can be thought of as the protective armor for our battery’s critical internals. A well-designed enclosure can mean the difference between a battery that lasts and one that fails prematurely. Given the diverse environments commercial vehicles operate in, our enclosures must be able to withstand the harshest of environments. 

To verify our premium battery packs’ resilience, we conduct several rigorous tests, including immersion and spray testing. 

• Immersion Testing: Battery pack enclosures are submerged in saltwater solutions to simulate prolonged exposure to harsh environments. This test ensures that our batteries remain impervious to water, even under extreme conditions such as flooding or heavy rain. 

• Spray Testing: This test subjects the battery enclosures to high-velocity water sprays and high-temperature steam. It simulates real-world scenarios, such as driving through heavy rain or puddles, ensuring that the enclosures can withstand these conditions without compromising performance. 

Additionally, our batteries are equipped with sensors that monitor items such as temperature, humidity, and voltage. These sensors detect any anomalies that could indicate a compromise in the battery’s safety, triggering our safety protocols to take appropriate action, ensuring continuous protection. 

Mechanical Reliability Testing 

Our battery pack is designed like a fortified structure. The enclosure acts as the foundation, walls, and roof, while the modules inside function as supportive beams. This robust design ensures that the battery can endure various stresses, from shock loads and vibrations to extreme weather, providing unmatched durability and strength. 

The synergy between the enclosure and the modules minimizes torsion, protecting the battery’s internal components from damage. This collaboration ensures the battery performs reliably, even under harsh conditions that commercial vehicles and industrial equipment frequently encounter. 

To ensure reliability, we run a series of mechanical tests, including vibration, impact, and crush testing, to verify the resilience of our batteries: 

• Vibration Testing: Battery packs in commercial applications experience constant vibrational stress from road conditions. We use a vibration table to simulate these stresses, representing up to a million miles of road wear, ensuring the battery can handle these vibrations without performance degradation. 

• Impact Testing: This test simulates extreme scenarios, such as hitting a manhole cover or a tow hitch. We fire projectiles at the battery enclosure at specific angles and speeds to test its resilience against such impacts. 

• Crush Testing: To further validate the enclosure’s integrity, we perform crush tests on all six sides of the battery using a hydraulic fixture that applies over 100 kN of force. This ensures the battery can withstand the forces of a vehicle crash, protecting the internal cells from damage. 

Characterization Testing 

Characterization testing involves a comprehensive analysis of the battery’s performance and behavior. This series of tests is crucial for understanding the battery pack’s capabilities and ensuring it meets the high standards of safety and reliability required for commercial applications. 

At Proterra, our design team uses characterization testing to validate whether the battery system meets performance, safety, and reliability requirements. The data from these tests helps refine the design and ensure the battery can handle the diverse conditions it will face. 

We conduct several types of characterization tests, including: 

• Capacity Testing: This measures the energy storage capability of the battery pack under specific conditions, ensuring it can deliver the required power over time. 

• Cycle Life Testing: Assesses the number of charge-discharge cycles the battery pack can undergo before performance degrades, crucial for understanding the battery pack’s longevity. 

• Thermal Performance Testing: Evaluates how well the battery pack can regulate temperature to prevent overheating, which is essential for safety and performance. 

• Abuse Testing: The battery pack is subjected to extreme conditions like short circuits, forced discharge, and overcharging to ensure it can handle potential real-world failures without catastrophic results. 

Cell Testing and Modeling 

The performance of our batteries begins at the cell level. Cell testing provides us with comprehensive data on the performance characteristics of the cells we use, ensuring that the entire battery pack meets our stringent performance standards. 

We use several methods to test the cells, including: 

• Calendar Testing: Evaluates cell degradation when batteries are idle, providing insights into their lifespan. 

• Cycle Aging Testing: Assesses how cells degrade over thousands of charge and discharge cycles, helping predict long-term performance. 

• Fast Charge Testing: Determines the most efficient methods for rapid charging, critical for minimizing downtime in commercial applications. 

• Temperature Testing: Examines charging performance under different temperature conditions, ensuring reliability across diverse environments. 

The data collected from cell testing is used to build accurate models that predict battery performance over time. This real-world data helps us refine our designs and ensure that our batteries will meet the demands of commercial vehicle applications throughout their lifecycle. 

Cell modeling involves analyzing the behaviors, traits, and capabilities of the battery cells. It allows us to predict how cells will perform under various conditions, helping us validate the performance and reliability of our battery systems before they are deployed in vehicles. 

At Proterra, we employ two types of cell modeling: 

• Electrochemical Modeling: This method relies on the physical principles governing cell behavior to predict performance, efficiency, and degradation. 

• Machine Learning Modeling: Using the extensive data we collect from cell testing, we extract valuable insights to enhance our understanding and predictions of cell performance. 

Through this comprehensive testing and modeling approach, we ensure that our batteries deliver optimal performance and reliability, supporting the demanding needs of commercial electric vehicles throughout their operational life. 

At Proterra, safety is our guiding principle. We back this with our state-of-the-art testing facility in our technology center in Burlingame, CA.