Electric Vehicle Battery Pack- Design, Components and Packaging

Lithium-ion batteries are highly efficient and more reliable than other batteries making them a good choice for electric vehicles. Despite the batteries being highly rated, some of the main deterring issues they face include; the thermal stability of Li-Ion batteries and high manufacturing costs. Many players and car manufacturers in the electric vehicle industry are today focused on optimizing battery designs. The main result most of them strive to achieve is to have batteries with increased energy storage that are safe, light in weight, and highly efficient. Most manufacturers aim to produce batteries that have regulated thermal conditions to improve the performance of EV battery packs.

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 Why the sudden change in the EV battery pack manufacturing industry? To understand EV batteries, let's discuss and get detailed information about how the battery pack design, components, and packaging of EV looks like.

Electric Vehicle Battery Pack Design

Electric vehicles' car battery packs have a complex system that consists of various components. Therefore, an efficient battery pack design is crucial for the success of an electronic vehicle. An EV battery pack contains various electro-mechanical systems that communicate with different sub-systems within the car. They also communicate simultaneously with multiple parameters through various interfaces. These interfaces include; mechanical, structural, thermal, electrical, control, and support. 

●Mechanical Communication through the various interfaces influences the reliability and safety of the battery pack, making it safer to drive an EV. It represents all the mechanical design features of an EV. These include damping pads, exhaust valves, cell spacers, and different seals that have been integrated within the battery pack for safety reasons.

●Structural- it is the general containment of the battery pack. It contains structural features such as tie-rods, end-plates, and cross-members that function as protective members in the battery pack. Therefore, a good battery pack has to have a case and a cover to prevent it from external and environmental factors (humidity, dirt, vibrations, and crash effects).

●The thermal interface controls the temperatures within the Lithium-ion battery cell between 25 and 30 degrees Celsius. It also ensures there is uniform thermal distribution within the battery pack to maximize energy capacity. It contains systems such as pumps, heat exchangers, coolants, and fans.

●The electrical interface generates and transmits a certain voltage to meet the power requirements of an EV. Its electrical circuit consists of a bus bar and cables, fuse, contactors, circuit breaks, and relays.

●Control systems monitor and regulate the state of a battery pack. The features are the Battery Management System and sensors used to measure current, voltage, humidity, pressure, and temperature within a battery pack.

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●Support interface is the support the battery pack gets from the vehicles. It is commissioned through mounting brackets and axles to help achieve the required degree of vibration isolation. Other systems include the chassis, floor, and car seats.

Electric Vehicle Battery Pack Components

An electric vehicle needs an enormous amount of power to perform effectively. An EV battery pack may vary slightly depending on the type of electric vehicle. But generally, these vehicles' battery packs contain three components; cells, modules, and a pack. An EV contains countless batteries that are installed in the form of modules and packs. Therefore, a cluster of battery cells does a module; a cluster of modules makes a pack, and hence the word battery pack.

●Cell

A cell is a basic unit that exerts electrical energy by charging and discharging to propel an EV. A cell is made of cathode, anode, separator, binders, and an electrolyte, all encompassed in an aluminum case. The cathode is the positive electrode that typically holds the most valuable recyclable material that is made up of many metals such as cobalt, aluminum, nickel, etc. On the other hand, the anode, which is a negative electrode, is composed mainly of silicon-based components, carbon or graphite.

●Module

A module is an assembly of battery cells put in a frame by combining a fixed number of cells to protect them from external factors like heat, shock, or vibrations. Modules are welded together to complete the electrical current flow path within an EV. These modules can also incorporate temperatures and cooling mechanisms and monitoring of the voltage produced by each battery cell.

●Pack

 A pack is the final shape of an EV battery. It is composed of modules and various control systems, including the Battery Management System, thermal management system, etc.; these control systems are responsible for communications with the vehicle outside the battery pack.

Electric Vehicle Battery Pack Packaging

An EV battery pack should be reliable and address issues that relate to impact resistance, thermal stability, and vibration isolation. While packaging a battery pack, there should be minimized mechanical and thermal interactions between the different units of a battery pack system to reduce the probability of the battery failing. There are critical factors and systems within a battery that have to be considered during packaging. These include the battery cell, gas exhaust nozzles, cell spacer type, insulation coating thickness, and the battery cooling system. These factors are crucial as they are the systems that make an EV operate safely and efficiently.

When it comes to packaging, the battery cell type is significant. Research proves that it is easier to improve the volumetric efficiency of a pack by packaging large quantities of smaller cylindrical cells. Packaging compactness has a positive impact on the thermal performance of a battery pack. The battery cell spacer type is also important in packaging. The battery cells are usually held together in their pre-specified places by rigid spacers. These spacers are friction fit and always depend on the type and shape of cells used. They are meant to be a right fit to restrict the movement of a battery cell or a module undergoing thermal regulation fluctuations. 

The battery pack packaging also includes a thermal management system. A pressure release valve is included in the packaging to minimize the safety risk posed to the EV in case of a battery failure due to high temperatures. 

Conclusion

Electric vehicle battery packs have to follow certain considerations when manufacturing and packaging. Manufacturers have to consider safety, efficiency in terms of mass and volume, serviceability, readiness for harsh conditions operations, cooling system implementation, handling, and operations.