The future of electric vehicles (EVs) holds significant importance for both consumers and manufacturers in the transportation industry. With a focus on reducing carbon emissions and addressing climate change, there is a growing emphasis and regulatory pressure on the production of EVs by automakers, aviation companies, and energy storage manufacturers.
In this context, major players in the automotive sector are engaged in a race to develop affordable electric cars that offer extended travel ranges on a single charge. The key to achieving this goal lies in the advancement of battery testing technology and batteries that last longer and charge faster than current formats. Encouragingly, researchers have made significant progress in designing lighter and more efficient batteries, thereby improving EV performance.
Here’s an overview of the types of batteries found in electric vehicles, their strengths and weaknesses, and the importance of battery testing in creating a greener future.
Types of Batteries in Electric Vehicles
While lithium-ion batteries have become the most prevalent in EVs, several varieties are powering tomorrow's technology, including nickel-metal hydride and lead-acid batteries. Let’s consider each of them.
Lithium-Ion Batteries
Easily the most popular batteries used in EVs today, lithium-ion batteries are ubiquitous due to their power-to-weight ratio. In other words, they are lighter and more energy dense than other types of batteries, enabling EVs powered by lithium-ion batteries to travel further on a single charge, relieving so-called “range anxiety.”
There are several different types of lithium-ion chemical combinations used in EV batteries:
Lithium cobalt oxide (LCO) batteries are relatively stable, but have lower capacities than other lithium alternatives. They’re also more vulnerable to thermal runaway when encountering severe abuse, such as high temperatures or overcharging. Furthermore, LCO batteries tend to have a shorter life span. Due to this, they are becoming less commonly used in EVs.
Lithium manganese oxide (LMO) batteries take advantage of their three-dimensional structure to enhance ion flow, improve current handling, and reduce internal resistance as they increase thermal stability and battery safety. This lowered internal resistance facilitates faster charging and high-current discharge.
Lithium nickel manganese cobalt oxide (NMC) combines the strengths of all three primary elements, creating an EV battery with a stable chemistry and high specific energy. Arguably one of the most innovative lithium-ion battery types, NMC has the disadvantage of being expensive due to the limited availability of cobalt.
Lithium iron phosphate (LFP) batteries have an iron-based cathode, rather than nickel, which helps reduce their cost of production. EVs powered by LFP can typically be charged 10,000 times and have the additional sustainability advantage of being recyclable. LFP batteries can accommodate faster charger rates and are less prone to catching fire when compared to their nickel counterparts.
While the iron components make LFP batteries less expensive, it also means they’re heavier than other alternatives, making range capacity a challenge. Given iron’s greater durability, drivers can also charge LFP batteries at a higher percentage.
Lithium nickel cobalt aluminum oxide (NCA) batteries offer high energy and a reasonably long life span. The inclusion of aluminum helps to stabilize the thermal and charge transfer resistance. Utilized on the cathode (positive pole of the battery), NCA has a capacity significantly higher than lithium cobalt oxide (LCO) and lithium iron phosphate (LFP). Their high energy density is made possible by NCA’s high voltage.
While they have exceptionally fast-charging capabilities, NCA batteries are expensive due to the rarity of cobalt and nickel.
Lithium titanate (LTO) batteries substitute the graphite in the anode with lithium titanate, creating an EV battery that charges faster than any other alternative on the market. Extremely safe, LTO batteries have excellent low-temperature discharge characteristics. Their thermal stability under high temperatures is superior to other lithium alternatives, but they're incredibly expensive.
Lithium-sulfur (Li-S) batteries tend to be less expensive than some of their counterparts because they rely on sulfur, which is highly available, rather than cobalt. However, due to their polysulfide effect, active material can gradually leak from the cathode, undermining the number of recharge cycles.
Nickel-Metal Hydride Batteries
These rechargeable batteries rely on nickel oxide hydroxide for a chemical reaction at the positive electrode. Their bipolar design helps them avoid short-circuiting. While they continue to be employed in numerous hybrid vehicles, nickel metal hydride batteries have predominantly been overtaken by lithium-ion batteries due to their superior attributes of reduced weight and higher energy density.
Lead-Acid Batteries
The oldest type of rechargeable batteries still used in EVs, lead-acid batteries were invented in 1859. Although lead-acid batteries are incapable of fast charging rates, their inexpensive nature means they remain surprisingly common today.
However, their low-energy density makes them less popular among car manufacturers seeking longer-range vehicles, and their high lead content means they are one of the least environmentally friendly battery options out there. Lead-acid batteries are what you’ll commonly find in gasoline-powered vehicles. They are becoming used less and less in electric vehicles as lithium-ion batteries have proven to be more energy efficient.
The Future: Solid-State Batteries
Solid-state batteries are an emerging technology that offers a promising solution for enhancing the capacity and performance of EV batteries. Unlike conventional lithium-ion batteries found in smartphones, power tools, and current EVs, which employ a liquid electrolyte solution, solid-state batteries utilize a solid electrolyte.
This fundamental difference brings several advantages.
Solid-state batteries eliminate the risks associated with flammable liquid electrolytes, resulting in improved safety and reduced fire hazards. Secondly, solid electrolytes enable the use of lithium metal anodes, which possess higher energy density than nickel metal hydride batteries.
This allows for increased battery capacity, providing EVs with extended driving ranges and improved overall performance. Additionally, solid-state batteries exhibit enhanced stability and durability, enabling them to withstand a greater number of charge-discharge cycles.
While still under development, the advancements in solid-state battery technology hold great potential for revolutionizing the EV industry by offering higher energy density, improved safety, and increased range—accelerating the transition to sustainable transportation.
However, some challenges remain, such as scaling up the production of large and affordable solid-state batteries, ensuring their longevity and reliability under various conditions, and testing their performance on the road.
Some examples of solid electrolyte materials that have been proposed or tested include ceramics (e.g., oxides, sulfides, phosphates), glass (e.g., lithium phosphorus oxynitride), and polymers (e.g., polyethylene oxide).
EV Battery Formats
Batteries have different features and characteristics depending on their shape or format. Here are some pros and cons of each kind:
Cylindrical batteries are the most common. They have electrodes and separators that are rolled up and placed inside a tube, enabling them to handle high pressure well because of their round shape. They are frequently used in power tools, e-bikes, and medical devices.
Prismatic batteries are similar to cylindrical, but are flat and square, with hard plastic or metal cases. They use space more efficiently than cylindrical ones, but have worse heat management. They also tend to be more expensive and prone to swelling. In addition to EVs, prismatic cells are also used in laptops, smartphones, and UPS systems.
Pouch batteries have soft foil cases that can bend and fit into various shapes. They are lighter and more flexible than the other types. They can also swell up to 10% after 500 cycles, but have extra space to accommodate the swelling. Unfortunately, they can be damaged by sharp objects.
Pack batteries are a group of individual cells connected together to provide power for EVs and come in different shapes and sizes depending on the type of cells used and design of the vehicle. This makes them heavier than other formats, hence many companies are shifting toward prismatic and pouch formats.
Why Testing EV Batteries Is Important
Battery testing is the cornerstone of guaranteeing batteries' reliability, durability, and security prior to their integration into the vehicles, devices, and energy storage systems that consumers rely on daily. Through the rigorous process of battery testing, manufacturers ensure their products perform precisely as intended.
Yet, the significance of battery testing extends far beyond its immediate application. It serves as a catalyst for pioneering research and the development of cutting-edge technologies. By subjecting batteries to various tests, engineers condition them to attain peak performance levels. Furthermore, every commercial industry, regardless of its nature, must undertake some form of testing to ensure the safety of its products for the welfare of consumers and end users alike.
The pivotal role of battery testing becomes even more pronounced in the realm of electric vehicles. Batteries represent the heart and soul of a vehicle's powertrain, serving as the reservoir and provider of energy to the electric motor. Consequently, battery testing profoundly influences the range, acceleration, and overall performance of EVs. Moreover, it is paramount in safeguarding the well-being of drivers, passengers, and other road users.
Now, let us contemplate for a moment the expanding EV market, encompassing not only sedans but also SUVs, trucks, buses, and an array of other vehicle types. Such diversification necessitates accounting for a wide spectrum of environmental conditions an EV may encounter in a single day's journey.
Whether traversing the arid heat of a desert, braving the corrosive coastal air, or enduring the chilling embrace of frigid mountain passes, an EV must bear the weight of its occupants while confronting the jolts and jounces of uneven roads. Consequently, companies must not only accommodate these varied circumstances but also the demands of city and highway driving.
In essence, battery testing is the bedrock upon which engineers establish the reliability, performance, and safety of batteries that power our daily lives. Through rigorous testing, companies ensure their products meet the exacting standards expected of them. The future of transportation, driven by electric vehicles, demands nothing short of meticulous battery testing to fulfill the promise of a sustainable and electrifying tomorrow.
Battery Testing Using Test Chambers
Battery test chambers can simulate different real-world environmental conditions and measure the effects on batteries. They are used for testing the safety and performance of batteries in various applications, such as electric vehicles, renewable energy storage, consumer electronics, and more.
Batteries are complex and sensitive systems that can be affected by factors such as temperature, humidity, altitude, vibration, and more. These factors can influence the battery’s capacity, life span, efficiency, and reliability. Moreover, some batteries, such as lithium-ion batteries, can pose significant safety risks due to their potential for a battery thermal event (BTE), fire, or explosion.
Battery testing involves exposing batteries to various environmental conditions and measuring their responses, such as voltage, current, capacity, temperature, and degradation. This crucial process can help identify potential hazards, optimize design parameters, evaluate quality and durability, and comply with industry standards and regulations.
While test chambers are designed to simulate different environmental conditions and measure various parameters of batteries, they can vary in size and capacity depending on the battery format and application. For instance, some battery test chambers can test small or medium-sized batteries in a reach-in chamber, while others can test large format prismatic cell batteries, or a larger amount of cells, in a walk-in or drive-in chamber.
Battery test chambers are also equipped with safety features that conform to the safety standards of different industries and applications. For example, some battery test chambers have gas detection sensors, pressure relief vents, fire suppression systems, purging systems with inert gas, electric door locks, intrinsic barriers, and more. These safety features are designed to prevent or mitigate any hazards that may occur during battery testing.
Testing Large Format Batteries for EVs
Before electric vehicles with large format batteries can be released to the market, rigorous testing is necessary to ensure their safety and performance. The purpose of battery testing is to push the batteries to their limits, identify potential failure points, and develop appropriate safety measures. Through this testing process, engineers aim to gain a comprehensive understanding of the batteries' true performance, set consumer expectations, and refine the battery design if necessary.
Testing large format batteries can be challenging and time-consuming due to the volatile nature of the materials involved. The risk of a BTE is a constant concern, and even a single defect can disrupt the entire product and could even damage the testing chamber. However, the ability to test a significant number of battery cells simultaneously brings manufacturers closer to delivering electric vehicles with improved performance.
Associated Environmental Systems (AES) offers industry-leading battery testing solutions to facilitate this testing process. One such solution is ATPHEAVY, designed for high-amperage testing of up to 1000 amps.
For added versatility, ATPHEAVY ADAPTABLE has universal terminals that can easily switch between different battery types and sizes. These systems can be integrated with AES's SC-512-SAFE, a benchtop chamber specifically designed for safe and efficient battery testing.
The environmental test chamber and battery cycler can be operated from a single control panel, allowing for synchronous operational activity, and temperature and cycling data can be collected in one location. Additionally, remote monitoring of the battery test chamber is available, enabling users to monitor the testing process from anywhere in the world.
By leveraging AES's advanced battery test chambers and different battery testing solutions, manufacturers can conduct efficient and thorough testing of large format batteries, bringing us closer to the widespread adoption of electric vehicles with enhanced performance and safety.
As a leader in designing and manufacturing temperature and humidity test chambers for some of the most innovative products you hold in your hand, drive down the road, and other things we can’t divulge, Associated Environmental Systems gets it. Reach out today to learn more about which battery testing solution is right for your lab.
