1. Introduction

With the rapid development of the new energy vehicle industry, a large number of power batteries are reaching the end of their useful life in vehicles. These retired power batteries, although no longer suitable for automotive applications due to capacity degradation and performance decline, still retain a significant amount of residual capacity, typically ranging from 60% 80% of their original capacity. Recombining these retired power batteries into modular energy storage solutions presents a win win opportunity. It not only addresses the environmental and economic challenges associated with battery disposal but also provides a cost effective alternative for energy storage needs. This approach aligns with the principles of the circular economy, promoting resource conservation and sustainable development.

 2. Technical Feasibility of Retired Power Battery Recombination

 2.1 Residual Capacity and Performance Assessment

The first step in the recombination process is to accurately assess the residual capacity and performance of retired power batteries. Advanced battery testing equipment is employed to measure parameters such as the state of charge (SoC), state of health (SoH), internal resistance, and voltage. By conducting comprehensive tests, batteries can be classified into different groups based on their performance characteristics. For example, batteries with similar SoH and internal resistance values are grouped together, as this ensures more balanced performance when they are recombined into a modular system.

Modern diagnostic techniques, including electrochemical impedance spectroscopy (EIS), can provide detailed insights into the internal condition of the batteries. EIS analyzes the impedance of the battery at different frequencies, which helps in detecting potential issues such as electrode degradation or electrolyte depletion. This information is crucial for predicting the remaining lifespan of the batteries and determining their suitability for recombination.

 2.2 Battery Sorting and Grouping

Once the performance assessment is complete, the batteries are sorted and grouped according to strict criteria. In addition to SoH and internal resistance, factors such as battery chemistry, size, and shape are also considered. Lithium ion batteries, which are commonly used in electric vehicles, come in various chemistries, including lithium iron phosphate (LiFePO4), nickel cobalt manganese (NCM), and nickel cobalt aluminum (NCA). Mixing different chemistries in a single modular system can lead to compatibility issues and safety risks, so batteries of the same chemistry are preferred for recombination.

Size and shape compatibility are also important, especially when designing modular systems with a specific form factor. Standardized battery modules are often designed to fit into pre determined enclosures, and ensuring that the recombined batteries can be neatly arranged within these modules is essential for efficient space utilization and thermal management.

 2.3 Electrical and Mechanical Recombination

The electrical recombination of retired power batteries involves connecting the batteries in series and/or parallel to achieve the desired voltage and capacity for the modular energy storage system. When connecting batteries in series, the voltages are added together, while in parallel, the capacities are combined. Specialized battery management systems (BMS) are integrated during the recombination process to monitor and control the charging and discharging of the battery modules.

The BMS plays a crucial role in balancing the charge and discharge currents among individual batteries within the module, preventing overcharging or over discharging of any single battery. This helps to extend the overall lifespan of the recombined battery system. Mechanically, the batteries are secured within the modular housing using shock absorbing materials and sturdy mounting structures to ensure stability during operation and transportation.

 3. Advantages of Retired Power Battery Recombination Modular Energy Storage

 3.1 Cost effectiveness

One of the most significant advantages of using retired power batteries for modular energy storage is the cost savings. Compared to new batteries, retired power batteries are much cheaper, often costing only a fraction of the price of new ones. The initial investment for a retired battery based energy storage system is significantly lower, making it an attractive option for a wide range of applications, from small scale residential energy storage to large scale commercial and industrial projects.

For example, in a commercial solar energy storage project, using retired power batteries can reduce the overall project cost by up to 50%. This cost reduction not only makes the project more financially viable but also allows for a faster return on investment. The lower cost also enables more widespread adoption of energy storage technology, especially in regions where the high cost of new batteries has been a barrier to entry.

 3.2 Environmental Benefits

Retired power battery recombination offers substantial environmental benefits. Improper disposal of lithium ion batteries can lead to the release of harmful heavy metals, such as cobalt, nickel, and lead, into the environment. By reusing these batteries in energy storage systems, the amount of battery waste sent to landfills or incinerators is significantly reduced.

Moreover, the production of new batteries requires a large amount of energy and resources, including mining for raw materials and manufacturing processes. Reusing retired batteries conserves these valuable resources and reduces the energy consumption associated with battery production. It is estimated that reusing retired power batteries can reduce the carbon footprint of energy storage systems by up to 70% compared to using new batteries, contributing significantly to global efforts to combat climate change.

 3.3 Energy Storage Flexibility

Retired power battery recombination modular energy storage solutions offer high flexibility in terms of capacity and application. The modular design allows for easy expansion or reduction of the energy storage system. If the energy storage requirements increase over time, additional battery modules can be added to the system. Conversely, if the demand decreases, modules can be removed.

These modular systems can be applied in various scenarios, including peak shaving in the power grid, backup power for commercial buildings, and energy storage for off grid solar and wind power systems. Their adaptability makes them suitable for both urban and rural environments, providing a reliable and flexible energy storage option for different users.

 4. Challenges and Solutions in Retired Power Battery Recombination

 4.1 Safety Concerns

Safety is a major concern when it comes to retired power battery recombination. Degraded batteries may have hidden internal defects, such as short circuits or thermal instability, which can pose a risk of fire or explosion. To address this, strict quality control measures are implemented during the battery selection and recombination process.

Batteries with signs of physical damage, such as cracks or bulges, are immediately rejected. Advanced monitoring systems are also integrated into the modular energy storage solutions. These systems continuously monitor parameters such as temperature, voltage, and current in real time. In case of any abnormal changes, the system can automatically disconnect the faulty battery module and trigger an alarm, ensuring the safety of the entire system.

 4.2 Performance Degradation and Lifespan

Retired power batteries, by nature, have already experienced some degree of performance degradation. As they are reused in energy storage systems, their performance may continue to decline over time at a faster rate compared to new batteries. To mitigate this, regular performance monitoring and maintenance are essential.

Battery management systems are designed to optimize the charging and discharging cycles of the recombined batteries, avoiding over stressing the batteries. Additionally, research is ongoing to develop new battery management algorithms and materials that can enhance the performance and extend the lifespan of retired power batteries. For example, the use of advanced thermal management systems can help regulate the temperature of the batteries, reducing the rate of performance degradation.

 4.3 Standardization and Compatibility

The lack of standardization in retired power batteries from different manufacturers and models poses a challenge for recombination. Batteries may have different terminal designs, electrical characteristics, and communication protocols. To overcome this, industry wide standards need to be established.

These standards should cover aspects such as battery size, electrical connection interfaces, and data communication protocols. By adhering to these standards, battery manufacturers can ensure that their retired batteries are more compatible with recombination processes. In the meantime, innovative adapter technologies are being developed to bridge the gap between non standard batteries and modular energy storage systems, enabling more seamless integration.

 5. Applications of Retired Power Battery Recombination Modular Energy Storage

 5.1 Grid connected Energy Storage

In the power grid, retired power battery recombination modular energy storage systems can be used for grid regulation purposes. They can store excess electricity generated during off peak hours, such as at night when electricity demand is low, and release it during peak demand periods, helping to stabilize the grid voltage and frequency.

These systems can also participate in ancillary services, such as frequency regulation and spinning reserve. By quickly responding to changes in grid conditions, they improve the overall reliability and efficiency of the power grid. In some regions, grid connected retired battery based energy storage projects have been successfully implemented, demonstrating their effectiveness in enhancing grid stability.

 5.2 Commercial and Industrial Energy Storage

Commercial and industrial facilities often have high and fluctuating electricity demands. Retired power battery recombination modular energy storage solutions can be installed on site to reduce electricity costs. By charging the batteries during off peak hours when electricity prices are low and using the stored energy during peak hours, businesses can significantly lower their electricity bills.

These systems can also serve as backup power sources during power outages, ensuring the continuous operation of critical equipment and minimizing production losses. For example, data centers, hospitals, and manufacturing plants can benefit from the reliable and cost effective energy storage provided by recombined retired power batteries.

 5.3 Residential Energy Storage

In the residential sector, retired power battery recombination modular energy storage systems offer homeowners the ability to store solar generated electricity for use at night or during cloudy days. This increases the self consumption rate of solar energy, reducing the reliance on the grid and lowering electricity bills.

Residential energy storage systems can also provide backup power during power outages, ensuring that essential appliances, such as lights, refrigerators, and medical equipment, remain operational. With the increasing popularity of home solar installations, the demand for cost effective energy storage solutions is growing, and retired power battery recombination systems are well positioned to meet this demand.

 6. Future Outlook and Development Trends

 6.1 Technological Innovation

The future of retired power battery recombination modular energy storage will be driven by continuous technological innovation. Research is focused on developing more accurate battery performance assessment methods, improving battery management systems, and enhancing the safety and reliability of recombined battery systems.

New materials and manufacturing processes are also being explored to further extend the lifespan of retired power batteries. For example, the development of advanced electrode materials and electrolytes can improve the electrochemical performance of the batteries, allowing them to be reused for a longer period. Additionally, the integration of artificial intelligence and machine learning algorithms into battery management systems will enable more intelligent and optimized operation of the energy storage systems.

 6.2 Policy and Regulatory Support

Policy and regulatory support will play a crucial role in the development of retired power battery recombination. Governments around the world are expected to introduce more favorable policies, such as subsidies, tax incentives, and regulations, to promote the reuse of retired power batteries.

These policies will encourage more investment in the research, development, and commercialization of retired battery based energy storage technologies. Standardization regulations will also be strengthened to ensure the safety and compatibility of recombined battery systems, facilitating their widespread adoption.

 6.3 Market Expansion

As the technology matures and the cost of retired power battery recombination modular energy storage continues to decrease, the market for these systems is expected to expand rapidly. The growing demand for energy storage in various sectors, including the power grid, commercial, industrial, and residential, will provide a large market space for retired battery based energy storage solutions.

In addition, emerging applications, such as electric vehicle to grid (V2G) technology, which allows electric vehicles to feed electricity back to the grid, may also create new opportunities for the reuse of retired power batteries. With the continuous growth of the electric vehicle market, the supply of retired power batteries will increase, further fueling the development of the retired battery recombination energy storage industry.