Need For Battery Balancing In Series And Parallel Configurations

Specifically, in applications that need the connection of numerous battery cells in series and parallel configuration, battery balancing is a vital factor of BMSs. The inherent differences and discrepancies among individual cells within a battery pack give birth to the need for battery balancing. Production differences, aging, temperature effects, or differing load conditions can cause these inequalities.

Series Configuration

Cells are joined end-to-end, and the same current moves through each cell in a series configuration. An imbalance arises due to any mismatch in the cell’s capacities or SOC. During the charging cycle, this imbalance may result in the overcharging of some cells and undercharging of other cells which causes inefficient use of the battery pack and potentially destroys the cells.

Decreased overall life of the battery pack and even safety issues can be seen with time when these imbalances are highlighted. For instance, a dangerous condition of uncontrollable rise of cell temperature known as thermal runaway can be the result of overcharging a single cell in a series arrangement.

Parallel Configuration

For sharing the load, cells are joined side-by-side in parallel configurations. Here, until equilibrium is attained, a difference in cell voltages can be the reason for the current to run from the greater voltage cell to the lower voltage cell. Imbalances in the SOC among the cells and energy losses can be the results of constant redistribution of current.

As compared to series arrangements, the risk attached to parallel arrangements is usually lower. However, inefficient energy use can still be caused by imbalances and may lead individual cells to wear at diverse rates, reducing the overall life anticipation of the battery pack.

In both setups, achieving equilibrium among cells is crucial to enhancing performance, prolonging lifespan, and upholding safety standards. By enabling the battery pack to work within safe and efficient factors, battery balancing strategies are used to equalize the voltages and the SOC among the cells. Numerous parameters such as the application’s particular needs, budget restrictions, and required efficiency are responsible for selection of ideal balancing techniques. All of these parameters are explained below in this chapter.

Conclusively, in advance battery system, the need for battery balancing in both series and parallel arrangements is imperative. It becomes an important part of modern BMS design by serving a pivotal role in maintaining the battery packs’ health, safety, and performance.

Passive Battery Balancing

Figure 2: Passive balancing

Overview And Operation Principle

Within a battery pack, the method used to equalize the charge state among individual cells is known as Passive Battery Balancing. The simplicity and cost-effectiveness are the key attributes of this technique. Through resistive parameters, passive balancing operates by releasing extra energy in cells with higher State-of-Charge (SOC), placing them in line with other cells having lower SOC.

Implementations

Bleeding Resistor: Passive Battery Balancing is commonly deployed as the bleeding resistor. A resistor is linked in parallel with each cell in this technique, and the cells having greater voltage selectively involves the resistor with the help of a control system. For equalizing the SOC with other cells, the extra energy is drained out as heat via the resistor.

Shunt Capacitor: In shunt capacitor technique, the parallel capacitors are connected with the cells and used to store energy from the greater voltage cells on temporary basis. Just like the bleeding resistor technique, this energy can then be slowly released through a resistor.

Advantages And Disadvantages

Advantages:

Simplicity: Passive balancing need very little extra elements, so it is comparatively easy to design and deploy.

Cost-Effectiveness: As compared to active balancing method, the passive balancing is cost-effective due to its simplicity.

Reliability: Lesser elements mean less failure points which usually result in a stronger system.

Disadvantages:

Energy Loss: The huge amount of energy is released in the form of heat which leads to energy loss, resulting in reduction of overall efficiency.

Heat Management: Specifically in high-power applications, the energy release in the form of heat may need added cooling options.

Limited Speed: As passive balancing depends on the slow energy depletion, it might be slower in addressing major imbalances between cells.

Within a battery pack, passive battery balancing plays an integral part in handling the equilibrium of SOC across the cells. It provides the simplicity and cost-effectiveness in the expense of energy efficiency, and might need extra examination for heat management. Several parameters such as desired balancing speed, energy efficiency inspection, and budget constraints influence its accuracy in a given application. All these parameters are further explained in this chapter.

Active Battery Balancing

Overview and Operation Principle

The charge levels in a multi-cell battery pack are equalized with the assistance of a latest method i.e., Active Battery Balancing. In contrast to passive balancing, where extra energy is simply depleted as heat, active balancing tries to redisperse this extra energy to other cells in the pack that need charging. Therefore, along with contributing to the overall efficiency of battery system, it reduces energy loss.

Implementations

Inductive Balancing: Through a common inductor, the energy from a higher charged cell is transmitted to a lower charged cell in inductive balancing. The energy flow between the cells is handled by controlled switches, and therefore, efficiently balance the charge.

Capacitive Balancing: In capacitive balancing, capacitors are used to store the energy for some time from a higher charged cell and transmitting it back to a lower charged cell. This technique might be more challenging but allows precision control and fast balancing.

DC/DC Conversion: Specialized converters are utilized to do energy transmission between cells in this method of DC/DC conversion. This technique is hugely adaptable and provides the benefit of controlled and isolated energy transmission.

Advantages and Disadvantages

Advantages:

Energy Efficiency: Rather than depleting excess energy, active balancing redisperses it, which increases overall efficiency.

Speed: For equalizing charge imbalances across the cells, active methods are usually quick.

Flexibility: Active balancing methods are easily adaptable to multiple applications and battery chemistries.

Disadvantages:

Complexity: Additional elements and control techniques make active balancing design more complicated.

Cost: In both components and design efforts, the greater complexity results in higher cost.

Potential for Interference: Careful inspection is required in the design as the electrical noise or interference might get introduced by the active elements.

An advanced method of managing an equal SOC across the battery pack’s cell is known as active battery balancing. Instead of dissipating the excess energy, the active balancing redistributes it, resulting in an increased efficiency and performance at the expense of elevated complexity and cost. Particular application requirements and restrictions are responsible for the selection between active and passive strategies (or combination thereof). All these topics will be further explained in the “Selection Criteria and Integration into BMS” subsection of this chapter.

Selection Criteria for Battery Balancing Techniques

The engineers ought to make a crucial selection between diverse balancing methods while developing a BMS requiring balancing. Both active and passive balancing approaches come with different pros and cons, and selecting one of them usually relies on numerous application specific factors. The primary criteria that will assist in selection is listed below:

1. System Efficiency

Passive Balancing: Higher energy loss leads to lower overall efficiency.

Active Balancing: Rather than dissipating it, redistribution of energy offers greater efficiency.

2. Complexity and Cost

Passive Balancing: Implementation is usually simpler and cheaper.

Active Balancing: Due to added elements and control techniques, it becomes more complicated and may result in more costly system.

3. Balancing Speed

Passive Balancing: Especially when the imbalances are crucial, it usually become slower.

Active Balancing: Specifically in large battery packs, it becomes speedier in equalizing the charge levels.

4. Energy Storage Capacity and Type

Passive Balancing: The smaller battery packs or applications where greater efficiency is not a critical aspect, passive balancing is enough.

Active Balancing: It is frequently used for huge systems where efficiency and precision control are imperative.

5. Reliability and Maintenance

Passive Balancing: Although limited elements mean potentially greater dependability, still it need more quicker maintenance due to energy loss.

Active Balancing: Due to complications, it may be prone to failure, but it still provides precision control and efficiency.

6. Environmental Considerations

Passive Balancing: For certain environments, dissipation of heat might not be ideal.

Active Balancing: It is ideal for applications where thermal management is a challenge.

7. Regulatory and Safety Requirements

Specifically in automotive or aerospace industries where strict rules are applied, compliance with safety and regulatory standards might impact the selection.

The application’s specific requirements, restrictions, and objectives must be fulfilled by the battery balancing method. In this decision-making procedure, the factors such as complexity, cost, speed, reliability, efficiency, environmental considerations, and regulatory compliance serve a crucial role.

The engineers can pick the most ideal method for a given application by comprehending these parameters and how they interplay with the features of active and passive balancing techniques. The combination of these balancing methods into a BMS will highlight the significance of this selection process which will be explained in the subsequent section.

Integration of Balancing Techniques into BMS

To ensures the optimal performance, life, and safety of a battery pack, merging of battery balancing techniques into a BMS is a crucial factor. To deliver the required functionality, balancing methods, whether passive or active must be integrated into the BMS. Let’s have a look at how merger takes place:

System Architecture Design

Understanding the Requirements: Specific needs of the application such as cost, size, efficiency, and reliability are the deciding factors to pick the one between passive and active balancing methods.

Designing the Balancing Circuit: It involves the selection of the correct components and layouts that put in order with the chosen balancing method. For instance, inductive, capacitive, or DC/DC conversion techniques are used in active balancing, whereas bleeding resistors or shunt capacitors are used in passive balancing.

Interfacing with Other Components: The other components of the BMS such as voltage and current sensors, microcontrollers, protection mechanisms, and communication modules ought to be perfectly interfaced with the balancing subsystem.

Control Strategies

Developing Control Algorithms: Based on the data collected by the BMS, deploy algorithms that handle the balancing procedure. Among passive and active balancing, the control technique may change significantly.

Real-time Monitoring and Adjustment: To make sure that all cells are managed at a similar SOC, continuously monitoring the status of each cell in the battery pack, and making real-time adjustments are important.

Protection Mechanisms

Implementing Safety Protocols: Incorporating of safety measures for overheating, overcharging, undercharging, and other unprotected conditions. This encompasses both hardware and software solutions that collaborate with the balancing technique.

Testing and Validation: To make sure that the balancing subsystem works as planned under numerous working scenarios, and comply to all safety standards, careful testing is needed.

Diagnostics and Maintenance

Implementing Diagnostic Tools: To identify any flaw or inefficiency in the balancing subsystem, diagnostic capabilities within the BMS needs to be embedded.

Maintenance Protocols: To ensure the extended effectiveness of the balancing subsystem, such as routine examinations, recalibrations, and element replacements if required, maintenance guidelines ought to be developed.

A deep knowledge of both the chosen balancing approach and the overall system structure of the BMS is needed for combining battery balancing techniques into a BMS. It consists of accurate control strategies, careful design, strong safety mechanisms, and complete diagnostics and maintenance methods.

Flawless integration is a must as it ensures that the balancing methods work effectively within the BMS, optimizing the battery pack’s performance, improving protection, and expanding its life. The engineers can make advanced BMSs to fulfil the continuously expanding needs of the cutting-edge battery-powered applications by comprehending the challenges involved in this integration.