Introduction

The concept of cell balancing in battery management systems (BMS) ensures that the energy distribution among the cells is balanced, allowing a greater percentage of the battery’s energy to be recovered. This is especially important for long battery strings that are used in scenarios that frequently require recycling. 

As per Grand View Research estimates, 

The global BMS market is experiencing remarkable growth, projected to surge from USD 7.19 billion in 2023 to USD 31.27 billion by 2030, demonstrating a powerful CAGR of 23.4%.

This highlights how crucial cell balancing in BMS is for businesses worldwide. Also, recent research in this field aims to achieve efficient battery usage through advancements in cell balancing in BMSs. 

Let us explore some of the crucial techniques for cell balancing and peek into the trajectory it can take in the future. 

Key Techniques of Cell Balancing in BMS

Let us look  into each of these cell balancing in BMS techniques:

Passive Cell Balancing 

With this method, cells having a higher State of Charge (SOC) are discharged via a bypass path, usually a resistor. Until the voltage of the higher SOC cells matches that of the lower voltage cells, the energy from those cells dissipates as heat. 

This approach is deemed to be user-friendly and reasonably priced, but it often wastes energy and may shorten battery life.

Active Cell Balancing 

Active cell balancing involves transferring charge from cells with higher SOC to those with lower SOC. This is achieved through energy transfer mechanisms such as inductive or capacitive charge shuttling. 

While this method is more efficient as it minimizes energy losses and maximizes efficiency, it is more complex and costly due to the need for additional components.

Lossless Balancing 

A method called lossless balancing involves bringing cells in and taking them out of the circuit while they are charging. This technique avoids energy loss by allowing the user to add or remove a cell from a pack when charging or discharging. 

However, in order to carry the entire current, a large number of switches must be used, increasing the system’s complexity and cost.

Redox Shuttle

This is a chemical approach as it involves adding a redox shuttle additive to the electrolyte of the battery. This additive shuttles between the cells and helps to maintain balance. 

While this method can be effective, it may impact the overall performance and lifetime of the battery.

Patents of Cell Balancing in BMS

Some of the recent patents related to cell balancing in BMS are as follows:

US20190109468A1

This patent describes an intelligent system for balancing the charge in battery cells. It combines two different techniques—active and passive balancing—to ensure that each cell gets the right amount of energy in different situations. 

This balancing act helps batteries last longer and perform better, which is especially important for lithium-ion batteries like those found in many electronics today. 

WO2017178023A1

This invention focuses on preserving consistent conditions across the battery’s cells, enabling the best possible performance in terms of longevity, stored energy, and efficiency. 

It consists of a cell monitoring block set up to track the voltage or a similar quantity across each battery cell in a module. 

The battery cell module’s positive and negative terminal voltages, the module’s output current, and the cell voltage of each cell are all monitored by a microprocessor.

US20140356656A1

This invention covers a technique for maximizing battery set performance and an intelligent battery management system. The batteries in a battery set can be automatically reassembled in series, parallel, mixed series-parallel, or mixed parallel-series configurations.

GB2600129A and GB2600129B

These patents cover a proactive battery management system (BMS) with lossless active buck balancing. Patents GB2600129A and GB2600129 B, which are extensions of GB2600129A, cover a pro-active battery management system (BMS) with lossless active buck balancing.

 This technology is intended to maximize a battery set’s performance by automatically recombining batteries in a battery set in a series connection, parallel connection, mixed series-parallel connection, or mixed parallel-series connection. 

The system may access every battery set’s cell, allowing for parameter measurement, charging, and discharging of every cell. As a result, batteries can be charged or drained to maximize efficiency.

US7851092B2

Redox shuttles for protecting lithium batteries from overcharging are covered in this patent. It offers an electrolyte with a redox shuttle addition for protection against overcharging that can withstand overcharging for thousands of hours.

US7811710B2

This patent describes a redox shuttle for rechargeable lithium-ion batteries. For overcharge prevention, it offers an aromatic compound replaced with at least one alkoxy group and one organic group containing tertiary carbon.

US20150221982A1

This patent covers high-voltage redox shuttles. It also offers specific instructions on how to create and use them in lithium-ion batteries and supercapacitors.

Case Studies Involving Cell Balancing in BMS

Now, let us review some case studies that highlight the practical implementation of cell balancing in BMS:

Passive Cell Balancing

A study conducted at the University of Shanghai for Science and Technology compared the performance of passive and active cell balancing techniques for Lithium-Ion Batteries. The bleed resistor-based passive cell balancing took more than 16000 seconds to reach a 0.01V difference for capacitors with 5F capacitance. 

Another study implemented a resistance-based passive control method in a novel BMS circuit topology.

Active Cell Balancing

The same study at the University of Shanghai for Science and Technology also examined active cell balancing techniques. The multi-winding flyback active cell balancing system reached a 2% difference in SOC in 1800 seconds. 

Another study implemented a bypass technique-based active balancing method in BMS. The voltage increase was measured at 0.155 V after 14 min in the active balancing mode.

Lossless Balancing

Research published in IET Power Electronics details an active cell balancing technique that uses a buck converter to balance a series of connected battery packs of lithium-ion cells. 

It was found to take 275 ms to balance three 3.7 V batteries, and thus, the model was found to respond faster.

Redox Shuttle

This Scientific Reports study titled ‘Battery deactivation with redox shuttles for safe and efficient recycling’ proposes a deactivation method using redox shuttles for safe and efficient recycling of spent lithium-ion batteries (LIBs). 

The addition of an RS with redox potentials located between the two electrode potentials into a LIB electrochemically induced an internal short circuit.

End Note: Future Scope of Cell Balancing in BMS

While current methods like passive and active balancing work, there’s room for improvement in cell balancing in BMS. 

Future research is likely to explore aspects such as: 

• Methods to combine these techniques for optimal efficiency: Focuses on integration strategies.
• Developing smarter balancing algorithms: Emphasizes innovation for improved battery cell balance.
• Using advanced materials for lower heat dissipation: Prioritizes thermal management solutions.
• Integrating AI and machine learning for predictive management: Leverages artificial intelligence for proactive battery care.
• Exploring new applications of these techniques in emerging fields such as electric vehicles and renewable energy storage systems: Highlights adaptability and cross-sector potential.