EV Battery Testing from Cell to Module to Pack

Though the power source in a hybrid or electric vehicle is commonly referred to simply as “a battery,” this piece of technology actually comprises dozens or even hundreds of individual battery cells. To function safely and efficiently, the individual battery cells are arranged into units called battery modules, and multiple battery modules are assembled into an even larger unit called a battery pack.

What is a battery cell?

A battery cell is the most basic unit of a lithium-ion battery, consisting of a cathode, anode, separator, and electrolyte inside a case. A battery cell by itself is typically between one and six volts and functions by converting chemical energy into electricity.

What is a battery module?

A battery module is an arrangement of multiple battery cells. It consists of many cells mounted into a frame that links them together, holds them in place and helps to protect them from external stressors like shock and vibration. As there is no standard number of cells required for a battery module, manufacturers design modules with different numbers of cells depending on the cells’ performance and the requirements of the final product design.

What is a battery pack?

A battery pack consists of multiple battery modules, mechanical packaging, and several additional pieces of technology meant to support and control battery function, such as a cooling system and a battery management system. The size, shape, and overall design of an EV battery pack is heavily influenced by the general design of the vehicle.

Testing battery cells vs. modules and packs

Battery cells, modules, and packs each require unique types of battery testing. Because battery cells function through chemical reactions, cell-level tests measure electrochemical performance in varying conditions. Stress, cycling, and environmental tests investigate the cells’ overall output and efficiency in addition to the safety of internal chemical reactions. Test sequences could include measurements of current, voltage, resistance, stability, and the rates of chemical reactions at different temperatures or in different environments. Battery cell testing occurs early in the overall design and manufacturing process of a battery-powered device.

The chemical functionality of battery cells is tested and verified before they are used in a pack application, so battery pack testing focuses on the engineering of the system overall. The testing regimen may include tests for durability, performance in specific use cases, application-specific safety, failure risks, and system-level interactions.

Modules and packs must undergo sub-system and system validation to verify that their engineering is sound and will meet all design specifications. By this stage of testing, the battery itself may be a secondary focus as the majority of tests will focus on the integrity of surrounding components.

Comprehensively testing hybrid and EV battery designs

When electric vehicles are being designed, it is never enough to know how an individual cell or module will perform independently. The manufacturer must know how the planned configuration of multiple cells and multiple packs together in a vehicle will impact performance, longevity, and the vehicle’s ability to operate safely. Electric vehicles are also a relatively new technology, compared to the internal combustion engine, and manufacturers still frequently encounter new questions and new variables related to battery performance because of this novelty.

To effectively address as many variables as possible, battery assemblies must go through thorough testing at the cell, module, pack, and full vehicle assembly stages. It is crucial that manufacturers include battery testing in the early phases of research and development to ensure the vehicle’s design and its expected performance are compatible with the proposed configuration of cells, modules, and packs. Precisely how these components are assembled can impact factors including the battery’s performance, heat distribution, and vulnerability to environmental conditions.

Specialized battery testing parameters

Element has reinforced our commitment to the future of automotive testing with several recent expansions and acquisitions.  Our acquisitions of Energy Assurance and Trialon have enhanced our battery testing capabilities, and our Detroit automotive lab is in the process of expanding its footprint to 60,000 square feet. With a decades-long history of providing testing and consultancy services to major automotive manufacturers, Element is the ideal partner to support you from research and development all the way through to full vehicle testing.

Our facilities are equipped to handle almost any type of battery test requirement, including custom test parameters, with the capacity to run multiple large and complex programs simultaneously. Element has the expertise to test even the most complex EV battery assemblies under real-world conditions, design custom testing standards for new product designs and provide expert guidance on unique testing procedures. To learn more, visit our hybrid and EV battery testing page or contact us directly.