Understanding Lithium-Ion Batteries in the EV Domain - part 3

This is the third part of a three-part series on lithium-ion batteries and their use in the EV domain. 

Electrical engineering students can get a glimpse into the popular batteries used in electronic gadgets and vehicles. The article exhibits the connection between series and parallel batteries and how they help in propulsion of the electric vehicles. 

The article also discusses the importance of a drive cycle of an electric circuit and its objectives of integration within it. Finally, it concludes on the dichotomy between batteries and DC sources. 

 

Battery World

Those looking for a fulfilling career in the battery domain of electrical engineering, must learn the process of translating cells into modules and finally into usable battery packages. 

An ideal battery is composed of one or more separate cells. Factors such as current, resistance, voltage, and time determine the storage capacity of these cells. 

Furthermore, different cell combinations result in developing various characteristics of a particular battery. Moreover, each cell requires a feasible formula to undergo an appropriate conversion to be commercially available in the future. 

In other words, the electrochemical process converts a small coin type cell into a massive 20kg heavy battery. The automotive industry necessitates this conversion in order to facilitate the smooth propulsion of its electric vehicles. 

 

Cells can be primarily classified into two types:

1. Cylindrical Cells

• Hard case cells

2. Prismatic Cells

• Hard case cells
• Pouch cells

 

Usually, mobile phones use pouch type cells in their technological fabrication. Next, a battery is an advanced composed of one or multiple cells. The different parts of a cell are: 

• Tab
• Housing
• Pressure valve
• Anode
• Cathode
• Separator

 

The Significance of Battery Management System in a Lithium-Ion Battery Package 

 

 

Li-ion batteries require a proper Battery Management System (BMS) for various reasons. Some of these reasons are listed below:

• Protection
• State of Charge
• Balancing
• Communication

 

Protection

• It is unsafe to charge and discharge Li-ion cells beyond and below their recommended limits.
• In this, the battery needs to be protected from overcurrents and short circuits.
• Additionally, temperature conditions must be kept under control during the charging and discharging of lithium-ion batteries.

 

State of Charge

• There must be an equilibrium between the current passing through the lithium-ion batteries and their voltages.
• This is because high voltage may lead to electrodes damage in the Li-ion battery.
• This may eventually result in the plating of lithium on the metallic anode tube and which may lead to poor battery performance.

 

Balancing

• The cells connected in series and parallel may engender different charge and discharge behaviours.
• Series connections require high voltage as compared to parallel connections.
• The high voltage batteries have cells divided into modules. In case of failure of a single cell, only the affected module needs to be replaced and not the entire cell.

 

Communication

• The Li-ion battery packs have the ability to communicate with other systems such as chargers, motor drives, etc.
• It also indulges in multiple kinds of serial and wireless communications with third party technological systems.
• Lithium-ion batteries operating at low voltages do not have the facility of internal communications.

 

The Conversion of a Cell into a Battery Pack

 

 

The conversion of a cell into a battery pack takes places through the following steps:

• Every battery comprises of two half cells (oxidation and reduction).
• These cells combine together to form a battery.
• The combination of these cells entails essential components of conversion.
• An ideal battery storage system comprises monitoring and control systems to help with the conversion procedure.
• This storage system also incorporates a storage device, SC switches, an AC Breaker, and an AC transformer for its proper functioning.
• A temperature control system regulates the entire battery storage.

 

The Drive Cycle of an Electric Circuit

The drive cycle of an electric circuit denotes the pattern of propulsion of an electric vehicle. Measurements of velocity per hour determine this drive cycle in electric vehicles. 

An electric vehicle requires a drive cycle for the following purposes:

• To examine the performance
• To interpret the battery state and consumption of energy
• To stimulate the model prior to scrutinizing its actual performance

 

State of Charge: The Remaining Capacity of a Battery

To determine the level of charge left in a battery circuit, electrical engineers need to study the well-rested voltage of the cell. 

For this, the voltage of a cell undergoes an accurate and a basic range modeling for its Statearge. In addition, if the battery lowers down the minimum level, it may suffer extreme damage. 

 

Block Parameters for HV Batteries

Some of the parameters for a Li-ion HV battery are listed below:

• Nominal voltage
• Internal resistance
• Battery charge capacity
• Self-discharge
• Ampere-per hour reading
• Temperature measurements

This is the process of translation of a lithium-ion cell into a proper battery. Also, there exists a distinction between batteries and DC sources -  batteries offer a limited capacity, while DC sources constitute an infinite capacity to propel electric vehicles. 

 

Conclusion

These series of blogs would have helped you, an electrical engineering student with the applications of Li-ion batteries for electric vehicles. It sums up the different features, uses, and aspects of a typical Li-ion battery in the automotive industry. 

If you are interested in entering the electrical engineering field, learning the dynamics of the different components of a lithium-ion battery is critical. Students must also know how their distinctive battery management system works to advance the optimal productivity of the vehicle. 

For more intensive knowledge on lithium-ion batteries, enrol yourself in a battery-technology course at Skill-Lync today.