Electronic devices and systems rely heavily on batteries and other energy storage systems for their power needs. These batteries are designed to provide power over some time, but as they discharge, they may not discharge evenly across all of their cells. This can lead to imbalances in the system, which can cause performance issues, safety concerns, and even premature failure. In addition, temperature differences between cells can also lead to such problems, which are often a result of a poorly designed thermal system for the battery pack.
Cell balancing is a critical aspect of battery management systems that maintains the uniformity of voltages across individual cells in a battery pack. This is essential to ensure the longevity, safety, and performance of the battery and to prevent the risk of overcharging or undercharging. There are two main cell balancing techniques- active and passive balancing.
But for that, first, let’s understand the importance of cell balancing.
The Importance of Cell Balancing in Electronic Devices
Cell balancing plays a critical role in maintaining the health and performance of electronic devices that rely on rechargeable batteries. When batteries are charged and discharged, the individual cells can become imbalanced, leading to reduced capacity, shorter runtime, and even premature failure.
Cell balancing technology ensures that the charge and discharge levels are distributed evenly among the cells, preventing imbalances that can compromise the performance and lifespan of the battery. This technology is crucial for devices that rely on high-capacity batteries, such as electric vehicles, laptops, and smartphones.
The Risks of Not Implementing Balancing
Failing to implement cell balancing in electronic devices and systems can result in severe risks. Apart from optimizing battery performance, cell balancing can also improve safety. When cells become imbalanced, there is an increased likelihood of overcharging, resulting in overheating, fires, or explosions. Cell balancing technology helps reduce this risk by ensuring each cell operates within a safe range, preventing overcharging and other hazardous situations.
Cell balancing is a critical component of battery management in electronic devices. Maintaining balanced charge levels and preventing hazardous conditions guarantees optimal performance and safety for a wide range of devices. Imbalanced batteries or energy storage systems can lead to reduced power output, shorter battery life, and potential damage to other system components, resulting in additional performance issues or safety hazards.
What is Active Balancing?
Active cell balancing is a technique that uses inductive charge shuttling or capacitive charge shuttling to transfer the charge between the cells. This method ensures that energy is transferred to where it is most needed rather than wasted. Active cell balancing is known for its efficiency and accuracy in maintaining cell balance. However, the main disadvantage of active cell balancing is its high cost and complexity. This method requires additional components to be added to the system, which can significantly increase the overall cost of the battery management system.
What is Passive Balancing?
On the other hand, passive cell balancing is a simpler and more cost-effective technique for balancing cells in a battery. The basic idea behind passive balancing is to discharge the cells through a bypass route that is mostly dissipative. This helps to ensure that all cells in the battery remain at a similar voltage level.
The idea is to remove a charge from the most charged cells in the pack by using passive shunt resistors. These resistors can remove up to 300mA per cell, which seems like a small amount but is more than enough for balancing very large battery packs.
Cell self-discharge rates are typically in the range of tens to hundreds of microamps (uA), much lower than the balancing current of 300mA. Even if there is a significant difference in the self-discharge rate of cells, say 1mA, the 300mA balancing current is still 300 times higher than the discharge rate. This means the shunt resistors can effectively maintain balance in the battery pack, even when the cells have varying discharge rates.
One of the main advantages of passive cell balancing is its simplicity. Because it does not require additional electronic components, passive balancing is easier to implement and maintain than active balancing. It is also a more cost-effective technique, as the bypass route can be externally integrated into the battery management system.
Active vs. Passive Cell Balancing
| Factor | Active Cell Balancing | Passive Cell Balancing |
| Cost | Very high cost due to the additional components required. | More cost-effective, as it does not require additional components. |
| Efficiency | It has very high efficiency, meaning it transfers energy to where it’s needed instead of wasting it. | Less efficient, as excess energy is dissipated as heat rather than being transferred to where it’s needed. |
| Complexity | It is highly complex, which makes it difficult to implement and maintain. | It is simple and easier to implement, as it does not require additional components or complex electronics. |
| Maintenance | It is a lot harder to maintain due to its complex design and additional components. | It requires less maintenance as it is a simpler system. |
| Energy Loss | It has very low energy loss as it transfers energy to where it’s needed. | It has comparatively high energy loss as excess energy is dissipated as heat rather than being used during discharge. |
As we can see from the table, active cell balancing has high efficiency and low energy loss, meaning it transfers energy to where it’s needed instead of wasting it. However, this comes at a high cost and with high maintenance requirements due to the additional components needed. It is also very complex, making it difficult to implement and potentially less reliable in the long term. On the other hand, passive cell balancing is more cost-effective due to its simplicity and the use of inexpensive components such as resistors.
Conclusion
In conclusion, after comparing and contrasting the factors of active and passive cell balancing, it can be concluded that passive cell balancing is often a better choice than active cell balancing for battery management systems. Passive cell balancing is an attractive option due to its simplicity and cost-effectiveness. Also, for larger battery packs, shunt resistors can effectively maintain balance in the battery pack, even when the cells have varying discharge rates. On the other hand, active cell balancing has higher complexity and cost, making it less suitable for many applications.
Furthermore, the amount of charge saved through active balancing is typically very less. Implementing active balancing for battery packs will also result in losses in charge up to 10-20% while transferring charge between cells.
In almost every case, passive cell balancing is sufficient to achieve the desired level of cell balancing, making it the preferred option for most battery management systems.
If you want to learn more about passive balancing batteries and how they can benefit your application, our team of battery experts is here to help. We have a wealth of experience designing and delivering high-quality battery solutions incorporating the latest passive balancing technologies. Contact us today to discuss your requirements, and we’ll work with you to find the optimal solution.
