1. Overview of Energy Storage Battery PACK
Energy storage battery PACK, also known as battery module or battery pack, is a device that connects multiple individual batteries in a specific series parallel manner and is equipped with corresponding management systems and protective measures to form an independent, rechargeable and dischargeable energy storage unit.
In the field of renewable energy, such as solar and wind power generation, due to their intermittency, energy storage batteries PACK are needed to store excess electricity for release when needed, ensuring a stable supply of electricity. According to statistics, with the rapid development of renewable energy, the demand for energy storage battery PACK is also constantly increasing. For example, in some large solar power plants, the energy storage battery PACK can store several megawatt hours of electricity, providing reliable power support for the grid.
In the field of electric vehicles, energy storage battery PACK is one of the core components. It provides power for electric vehicles, determining their range and performance. At present, lithium-ion batteries are the main choice for electric vehicle energy storage battery PACK, with high energy density and long cycle life. For example, some high-end electric vehicles have energy storage batteries with a PACK capacity of over 100kWh and a range of over 500 kilometers.
In summary, energy storage battery PACK plays a crucial role as a key component for energy storage and output in fields such as renewable energy and electric vehicles. It can not only improve energy efficiency, but also reduce dependence on traditional fossil fuels, contributing to achieving sustainable development.
2. Design points and case analysis
(1) Design points
a. Explosion proof design, using PUW explosion-proof valves for timely pressure relief to prevent explosion hazards.
Once the lithium-ion battery pack experiences thermal runaway, the air pressure inside the pack will rapidly increase, posing a risk of explosion. PUW explosion-proof valves can quickly and promptly release pressure in such situations. For example, in some energy storage projects, battery packs equipped with PUW explosion-proof valves have successfully avoided explosions in the event of thermal runaway, ensuring the safety of personnel and equipment.
b. Maintain the balance of internal and external air pressure to ensure the safety and reliability of the battery.
Because the temperature of the battery pack changes during the charging and discharging process, resulting in changes in the air pressure inside the pack. The PUW explosion-proof valve is breathable and leak proof, maintaining the same air pressure inside the bag as the outside world. According to statistics, battery packs designed in this way can effectively reduce the performance degradation and safety hazards caused by changes in air pressure, and improve the reliability and service life of batteries.
c. Consider the design of the management system to ensure safety performance such as overcharging and overdischarging.
Factors such as overshoot, overdischarge, overheating, detection accuracy, and battery balance should be considered to ensure the safety and reliability of the battery. A management system that has been reasonably designed and validated by the market can monitor the status of the battery in real time, take timely measures in case of abnormal situations, and protect the battery from damage. For example, some advanced management systems can precisely control the charging and discharging process of batteries, minimizing the risks of overcharging and overdischarging.
d. Mechanical structure design, taking into account factors such as strength, seismic resistance, and heat dissipation.
When designing energy storage battery PACK, factors such as strength, shock resistance, heat dissipation/heating, waterproofing, and dust prevention should be considered. For example, using high-strength materials and reasonable structural design can improve the mechanical strength of battery packs, enabling them to withstand certain external impacts; Good heat dissipation design can effectively reduce the temperature of the battery, improve its performance and lifespan.
e. Waterproof and seismic design to prevent damage to the internal structure of the battery.
After soaking the lithium battery cell, the positive and negative poles will short circuit and continue to discharge, which will cause damage to the internal structure of the battery. Therefore, waterproof and dustproof performance should be considered in the design of battery packs. At the same time, seismic performance should be considered to adapt to different usage environments. For example, in some harsh environments such as earthquake prone areas or complex outdoor terrain, waterproof and seismic design is particularly important.
f. Pay attention to temperature effects and optimize battery performance and lifespan.
The "heat" factor greatly affects the structural design of battery pack PACK. Lithium ion battery energy storage battery packs are sensitive to temperature environments, and high temperatures can seriously affect the battery's charging and discharging performance and many characteristic parameters, such as internal resistance, voltage, SOC, available capacity, charging and discharging efficiency, and battery life. Through reasonable thermal management design, such as using liquid cooling or air cooling technology, the temperature of the battery can be effectively controlled, and the performance and lifespan of the battery can be improved.
g. Material selection to ensure high voltage insulation performance and structural strength.
High voltage insulation resistance is one of the most important technical requirements for battery pack structure design. Generally, nylon with high strength and plasticity can be used as raw material, and 5% to 45% glass fiber can be added to the material for GF strengthening, which can improve the structural strength and vibration resistance. This material selection can ensure the safe operation of the battery pack under high voltage, while improving its structural strength and vibration resistance.
(2) Design case
a. Design case of liquid cooling plate, analyze the characteristics and key selection of different types of liquid cooling plates.
Liquid cooled plate is an important component of thermal management for energy storage battery PACK. Different types of liquid cooled plates have different characteristics. For example, some liquid cooled plates have efficient heat dissipation performance, but the cost is relatively high; Some liquid cooled plates have lower costs, but their heat dissipation performance is relatively weak. When choosing a liquid cooled plate, it is necessary to comprehensively consider factors such as heat dissipation performance, cost, and reliability. For example, in some application scenarios that require high heat dissipation performance, liquid cooled plates with better heat dissipation performance can be chosen; In some application scenarios with high cost requirements, low-cost liquid cooled plates can be chosen.
b. LG's energy storage module and Pack design analysis, exploring its advantages from product portfolio, structural design, and other aspects.
LG's energy storage module and pack design have many advantages. From the perspective of product portfolio, LG's battery cells are divided into energy type and power type based on different sustained power discharge rates, meeting different application needs. In terms of structural design, LG adopts a standardized combination of small and large modules, which are then grouped together. In the field of non high intensity vibration, the structure of the modules is oriented in the longitudinal direction, based on the basic structure of CMA, and several modules are stacked to form a long large module structure. This design has good scalability and flexibility, and can adapt to different energy storage system requirements.
c. Simulation calculation and experimental research on thermal design of new energy storage battery packs, elaborating on key parameter analysis and research results.
The simulation calculation and experimental research on the thermal design of new energy storage battery packs are of great significance for improving the performance and reliability of energy storage batteries. Through simulation calculations, the impact of different thermal management strategies on battery temperature distribution and performance can be analyzed, providing theoretical support for thermal design. Meanwhile, through experimental research, the accuracy and effectiveness of the simulation model can be verified, and optimized thermal design schemes can be proposed. For example, some studies have conducted in-depth discussions on the thermal design of lithium battery packs in energy storage systems through a combination of simulation calculations and experimental research. A multi-objective optimization based thermal design method has been proposed, which comprehensively considers factors such as battery performance, safety, and economy for optimization, and has achieved good research results.
3. Composition and Technical Parameters
(1) Component
a. Single cell battery, responsible for energy storage and release.
The commonly used single-cell batteries currently include lithium-ion batteries, lead-acid batteries, nickel hydrogen batteries, etc. Lithium ion batteries play an important role in energy storage battery PACKs due to their high energy density and long cycle life. For example, in some high-end electric vehicle energy storage battery PACKs, lithium-ion batteries can provide powerful power support with a capacity of up to several hundred ampere hours. Although lead-acid batteries have relatively low energy density, their cost is low and they are still widely used in some cost sensitive application scenarios. Nickel hydrogen batteries have good charging and discharging performance and safety, and also have a certain market share in some energy storage fields.
b. Battery management system, monitoring battery status and protecting battery safety.
The Battery Management System (BMS) is one of the core components of the Energy Storage Battery PACK. It achieves precise control of the battery state by measuring parameters such as voltage, current, and temperature. BMS can monitor the charging and discharging status of batteries in real time to prevent overcharging, overdischarging, overcurrent and other situations from occurring. For example, when the battery level approaches full, the BMS will automatically reduce the charging current to avoid overcharging; When the battery level is too low, the BMS will issue an alarm to remind the user to charge it in a timely manner. In addition, BMS can also balance the management of batteries, ensuring that the power of each individual battery remains consistent, and improving the overall performance and lifespan of the battery pack.
c. Thermal management system to maintain a suitable temperature range.
The thermal management system is responsible for maintaining the energy storage battery PACK within a suitable temperature range to prevent damage to the battery due to overheating. Common thermal management methods include air cooling, liquid cooling, etc. The air cooling system blows air over the surface of the battery through a fan, taking away heat. The liquid cooling system lowers the battery temperature by circulating the coolant. For example, in some high-power energy storage systems, liquid cooling systems can more effectively control battery temperature, improve system stability and reliability. Generally, the system temperature difference is required to be ≤ 5 ℃ to ensure the stability of battery performance.
d. Electrical system, responsible for the transmission and distribution of electrical energy.
The electrical system includes wires, cables, connectors, etc. that connect components such as batteries, BMS, and thermal management systems, responsible for the transmission and distribution of electrical energy. The high-voltage wiring harness can be seen as the "main artery" of the battery pack, continuously delivering battery energy to the end load; The low-voltage wiring harness can be seen as the "neural network" of the battery PACK, which transmits real-time detection and control signals. The design of electrical systems needs to consider factors such as current magnitude, voltage level, and insulation performance to ensure the safe transmission of electrical energy.
e. Box and bracket to protect internal components.
The box and bracket are used to accommodate and protect all components inside the energy storage battery PACK, preventing external environmental interference and damage. The box is usually made of high-strength materials, which have good impact resistance, vibration resistance, and waterproof and dustproof performance. The bracket plays a role in supporting and fixing the internal components of the battery PACK, ensuring that the battery PACK can remain stable in various usage environments.
(2) Technical Parameter
a. Capacity, measuring the ability to store electrical energy.
Capacity is an important indicator for measuring the energy storage capacity of an energy storage battery PACK, usually measured in ampere hours (Ah) or kilowatt hours (kWh). The larger the capacity, the more energy the energy storage battery PACK can store. For example, a 100kWh energy storage battery PACK can provide several days of electricity supply for a household. In practical applications, it is necessary to choose the appropriate capacity of energy storage battery PACK according to different needs.
b. Energy density, reflecting performance advantages and disadvantages.
Energy density refers to the amount of electrical energy that can be stored per unit mass or unit volume of an energy storage battery PACK, typically measured in watt hours per kilogram (Wh/kg) or watt hours per liter (Wh/L). The higher the energy density, the better the performance of the energy storage battery PACK. At present, the energy density of lithium-ion batteries is relatively high, for example, the energy density of some high-end lithium-ion batteries can reach over 200Wh/kg. Improving energy density can reduce the volume and weight of energy storage battery PACKs, enhancing their portability and applicability.
c. Charging and discharging efficiency determines energy conversion efficiency.
Charge and discharge efficiency refers to the efficiency of energy conversion during the charge and discharge process of an energy storage battery PACK, usually expressed as a percentage. The higher the charging and discharging efficiency, the higher the energy utilization rate of the energy storage battery PACK. Generally speaking, the charging and discharging efficiency of lithium-ion batteries can reach over 90%. Improving charging and discharging efficiency can reduce energy loss and lower usage costs.
d. Cycle life, reflecting the service life.
Cycle life refers to the number of times an energy storage battery PACK can maintain a certain performance during charge and discharge cycles. The longer the cycle life, the longer the service life of the energy storage battery PACK. For example, the cycle life of some high-quality lithium-ion energy storage battery PACKs can reach thousands or even tens of thousands of times. In practical applications, it is necessary to select energy storage battery PACKs with appropriate cycle life according to different usage scenarios and requirements.
e. Safety, including various protective measures and thermal management systems.
Safety is one of the important technical indicators of energy storage battery PACK, including protection measures against overcharging, overdischarging, overcurrent, short circuit, as well as thermal management systems. Good safety can ensure the reliability and stability of energy storage battery PACK during use. For example, the perfluorohexane fire extinguishing device can quickly suppress the spread of fire in the event of a PACK battery pack fire, providing strong protection for the safety of the PACK battery pack. Meanwhile, the thermal management system can effectively prevent safety accidents caused by battery overheating.
4. Design process and analysis methods
(1) Design process
a. Select and grade battery cells to ensure consistent performance.
In the design process of energy storage battery PACK, the selection and grading of battery cells are crucial first steps. Firstly, it is necessary to select suitable lithium battery cells from reliable suppliers. For some high-end energy storage applications, lithium-ion battery cells with high energy density and long cycle life may be chosen. In the selection process, strict testing should be conducted on the performance parameters of battery cells, including capacity, internal resistance, voltage, etc. According to statistics, by testing and grading a large number of battery cells, the consistency of performance and quality can be ensured to be over 98%. After classification, battery cells can be stored according to different performance levels to prepare for subsequent assembly work.
b. Assemble battery cells using appropriate connection methods.
Battery cell assembly is the process of combining multiple battery cells according to design requirements. At this stage, effective connection methods such as welding or crimping need to be used. The welding method has the advantages of firm connection and low resistance, but it is difficult to operate and requires high process requirements. The crimping method is relatively simple, but the stability of the connection may be slightly inferior. For example, in some large-scale energy storage battery PACK production, laser welding technology may be used to connect battery cells together. This welding method has the advantages of high energy density, small welding deformation, and small heat affected zone, which can effectively improve the accuracy of the workpiece, make the weld smooth, impurity free, uniform and dense, and also achieve welding between different materials, meeting the welding needs of various materials. By selecting a reasonable connection method, reliable connections between battery cells can be ensured, providing guarantees for the performance of energy storage battery PACK.
c. Integration of battery management system to achieve monitoring and protection functions.
The Battery Management System (BMS) is one of the core components of energy storage battery PACK, and its integration is crucial for achieving monitoring, balancing, and protection functions of battery cells. When integrating BMS, it is necessary to accurately connect and debug it with the battery cell. BMS can monitor the voltage, current, temperature and other parameters of battery cells in real time. By analyzing these parameters, it can achieve charge and discharge control, balance management and fault diagnosis of the battery. For example, when the voltage of a battery cell is too high or too low, the BMS can automatically adjust the charging and discharging current to prevent overcharging or overdischarging; When the temperature of the battery cell is too high, the BMS can activate the cooling system to reduce the battery temperature and ensure the safe operation of the battery. In addition, BMS can also exchange data with external devices through communication interfaces to achieve remote monitoring and management of energy storage battery PACK.
d. Encapsulation of the shell provides safety and heat dissipation protection.
Shell encapsulation is the process of installing a battery pack inside a casing to ensure safety and stability, as well as provide heat dissipation and protection functions. The selection of the shell needs to consider multiple factors, including material strength, heat dissipation performance, waterproof and dustproof ability, etc. For example, some high-performance energy storage battery PACKs may use aluminum alloy shells, which have advantages such as high strength, light weight, and good heat dissipation performance. During the packaging process of the casing, it is also necessary to ensure a secure installation between the battery pack and the casing to prevent loosening or displacement during use. At the same time, the casing also needs to have a good heat dissipation design, which can dissipate the heat generated by the battery pack in a timely manner through heat dissipation fins, ventilation holes, etc., to ensure that the working temperature of the battery is within a safe range. In addition, the casing also needs to have certain waterproof and dustproof capabilities to protect the battery pack from external environmental influences.
e. Conduct overall testing and quality control to ensure product performance.
Overall testing and quality control are the final step in the design process of energy storage battery PACK, and are also key links to ensure product performance. At this stage, it is necessary to conduct comprehensive testing on the assembled module pack, including performance testing, capacity testing, cycle life testing, and security testing. Performance testing mainly includes testing of parameters such as charging and discharging efficiency, response time, etc; Capacity testing measures the actual capacity of a battery by charging and discharging it; Cycle life testing simulates the charging and discharging cycles of a battery in actual use to evaluate its lifespan performance; Safety testing includes overcharge, overdischarge, short circuit, impact and other tests to ensure that the battery can still operate safely under various extreme conditions. Through strict testing and quality control, the performance and quality of energy storage battery PACK can be ensured to meet design requirements, providing users with reliable energy storage solutions.
(2) Analysis method
a. Interpret the definition of PACK and understand its technical core.
Lithium ion battery PACK, also known as battery module, is a manufacturing process for lithium-ion batteries, which means packaging, encapsulation, and assembly. It refers to connecting multiple sets of lithium-ion single cells in series and considering issues such as system mechanical strength, thermal management, BMS matching, etc. Its important technologies are reflected in the overall structural design, welding and processing process control, protection level, active thermal management system, and other aspects. For example, connecting two batteries in series or parallel to form a specific shape according to customer requirements is called PACK. By interpreting the definition of PACK, it can be clarified that its technical core lies in the reasonable combination and packaging of multiple individual batteries to meet different application needs.
b. Analyze the composition of PACK and understand the roles of each part.
The battery PACK mainly consists of individual battery modules, electrical systems, thermal management systems, enclosures, and BMS. A single battery module is a storage and release unit for electrical energy, equivalent to the "heart" of the human body; The electrical system is responsible for the transmission and distribution of electrical energy, with high-voltage harnesses such as "arterial blood vessels" and low-voltage harnesses such as "neural networks"; The thermal management system maintains the battery operating within a suitable temperature range, like installing an "air conditioner" on the battery; The box and bracket play a role in supporting, resisting mechanical impact, mechanical vibration, and environmental protection, similar to the "bones" of the human body; BMS is the "brain" of the battery, responsible for monitoring the battery status, managing the charging and discharging process, and protecting the battery from damage such as overcharging, overdischarging, and overcurrent. By analyzing the composition of PACK, we can gain a deeper understanding of the roles of each component, providing a basis for designing and optimizing energy storage battery PACK.
c. Explore the characteristics of PACK and clarify technical requirements.
PACK lithium battery pack requires the battery to have a high degree of consistency (capacity, internal resistance, voltage, discharge curve, life), with a cycle life lower than that of a single battery. It should be used under limited conditions, protected after molding, and monitored for charging balance, temperature, voltage, and overcurrent. It must meet the voltage and capacity requirements of the design. For example, in practical applications, strict control and optimization are required in battery cell selection, assembly processes, BMS design, and other aspects to meet these characteristics and technical requirements. By exploring the characteristics of PACK, the technical requirements in the design process can be clarified to ensure the performance and quality of energy storage battery PACK.
d. Introduce the PACK method, including serial parallel composition and process selection.
The battery module is composed of individual cells connected in series. Parallel connection increases capacity without changing voltage, while series connection doubles voltage without changing capacity. When selecting battery cells, it is required to have consistent types and models, with differences in capacity, internal resistance, and voltage values not exceeding 2%. The main processes of PACK include laser welding, ultrasonic welding, pulse welding, and contact with elastic metal sheets. Taking into account production yield, efficiency, and internal resistance of connection points, laser welding is currently the preferred choice for many battery manufacturers. For example, if 15 cells with a voltage of 3.2V are connected in series, it will be 48V, which is called series boost; A battery cell with a capacity of 50Ah, when connected in parallel, has 100Ah, which is called parallel expansion. By introducing the PACK method, specific technical solutions and process choices can be provided for the design of energy storage battery PACK.
e. Understand PACK technical parameters and master product performance indicators.
Combination method: 1P24S represents 24 series and 1 parallel, with voltage doubled after series connection. The rated voltage is 3.2 * 24=76.8V. Rated capacity refers to the capacity of a battery that can operate continuously for a long time under rated working conditions, measured in ampere hours (Ah). It is the product of the discharge current in ampere hours (A) and the discharge time in hours (h). For example, 280Ah represents discharging at a maximum rate of 0.5C for 2 hours. Rated energy=nominal capacity (Ah) * nominal voltage (V). Charge and discharge efficiency refers to the efficiency of energy conversion during the charge and discharge process of an energy storage battery PACK, usually expressed as a percentage. Cycle life refers to the number of times an energy storage battery PACK can maintain a certain performance during charge and discharge cycles. Safety measures include protection against overcharging, overdischarging, overcurrent, short circuit, as well as thermal management systems. By understanding the technical parameters of PACK, one can grasp the performance indicators of the product and provide reference for the selection and application of energy storage battery PACK.