5 minutes to get the basics of the lithium battery PACK

Lithium-ion battery PACK technology represents a critical manufacturing process within the energy storage industry, fundamentally involving the packaging, encapsulation, and assembly of multiple lithium-ion individual battery cells. This process connects cells in series and parallel configurations while meticulously addressing system mechanical strength, thermal management, and Battery Management System (BMS) integration16. The sophistication of this technology is demonstrated through holistic structural design, welding and processing工艺控制, ingress protection ratings, and active thermal management systems. For instance, connecting two battery cells in series or parallel according to specific customer requirements to form a particular shape constitutes a basic PACK unit1. The global significance of this technology is underscored by market projections indicating the lithium-ion battery anode market will soar from USD 19.06 billion in 2025 to USD 81.24 billion by 2030, achieving a robust compound annual growth rate (CAGR) of 33.6%2. This growth is propelled by the cost-effectiveness and sustainability of these solutions for renewable energy storage, ideal for managing fluctuations inherent in wind and solar power generation2.

The Core Components of a Lithium Battery PACK

A lithium battery PACK is a sophisticated system integrating several essential components that work in concert to ensure safety, efficiency, and reliability. Understanding these components is fundamental to appreciating the engineering behind modern energy storage solutions.

1. Battery Cell Modules

The battery cell modules serve as the very "heart" of the entire lithium battery PACK, responsible for the fundamental storage and release of electrical energy16. These modules are constructed from individual lithium-ion cells meticulously organized in precise series and parallel configurations to achieve the desired voltage and capacity ratings. The performance of the entire PACK hinges critically on the high consistency of these individual cells concerning their capacity, internal resistance, voltage, discharge curves, and overall lifecycle1. Even a minor variance exceeding 2% in these parameters can lead to significant imbalances, reducing overall efficiency and potentially creating safety hazards. Manufacturers, therefore, implement rigorous grading and matching processes to ensure that only cells with nearly identical characteristics are combined within a module, thereby optimizing the pack's performance and longevity.

2. Electrical Systems

Functioning as the "arteries and nervous system" of the battery PACK, the electrical system is paramount for efficient power transmission and precise communication1. It primarily consists of robust connecting copper busbars, high-voltage wiring harnesses, low-voltage wiring harnesses, and various electrical protection devices. The high-voltage lines are engineered to carry substantial currents, acting as the main conduits that deliver power from the battery to the external load, such as an electric vehicle's motor or a grid-tied inverter6. Conversely, the low-voltage harnesses are dedicated to transmitting sensitive sensor data and control signals between the BMS, cell modules, thermal management system, and external controllers. This intricate network ensures real-time monitoring of critical parameters and enables swift responses to operational commands and fault conditions, guaranteeing stable and managed operation.

3. Thermal Management Systems

Lithium-ion cells generate heat during charging and discharging cycles, and managing this heat is crucial for safety and longevity. The thermal management system acts like an "air conditioner" for the PACK, maintaining an optimal operating temperature range and minimizing internal temperature gradients, typically to within 5°C16. Two primary methods are employed: air-cooling and liquid-cooling. Air-cooling utilizes fans to circulate air over the modules, while liquid-cooling, which can be further categorized into cold-plate and immersion cooling, employs a coolant fluid to absorb and transfer heat away more efficiently1. Liquid-cooling is increasingly favored for high-density applications due to its superior heat transfer capabilities. By preventing overheating and ensuring even temperature distribution, this system directly contributes to enhanced safety, prevents thermal runaway, and significantly extends the battery's cycle life.

4. Structural Enclosure

The structural enclosure forms the "skeleton" of the battery PACK, providing essential mechanical support, ensuring structural integrity, and protecting the internal components from environmental hazards16. Typically constructed from materials like aluminum or steel, the enclosure includes a main箱体, cover plates, metal brackets, panels, and fastening screws. Its design is critical for withstanding mechanical shocks, vibrations, and environmental stresses encountered during operation. Furthermore, the enclosure is sealed to achieve specific Ingress Protection (IP) ratings, safeguarding the sensitive electronics and cells against dust and moisture intrusion. A well-designed enclosure not only ensures the physical safety of the components but also contributes to the overall thermal management by potentially incorporating cooling channels or heat dissipation features.

5. Battery Management System

The Battery Management System (BMS) is unequivocally the "brain" of the operation, continuously overseeing and managing all aspects of the battery PACK's functionality16. This sophisticated electronic system is responsible for accurately measuring key operational parameters, including individual cell voltages, pack current, and temperature at multiple points. Beyond mere monitoring, the BMS executes vital functions such as cell balancing to maintain voltage uniformity across all cells, state-of-charge (SOC) and state-of-health (SOH) estimation, and implementing protective protocols against over-voltage, under-voltage, over-current, and short-circuit conditions. By processing this data, the BMS ensures the pack operates within its safe operating area (SOA), maximizes its usable capacity, and provides critical communication links to external systems, such as cloud-based monitoring platforms or vehicle control units, for comprehensive energy management.

Manufacturing Processes and Technical Specifications

The assembly of a lithium battery PACK is a meticulous process that demands precision and adherence to strict technical specifications to ensure ultimate reliability and performance.

Series-Parallel Configuration

The foundational design of a battery module is based on connecting individual cells in series and parallel configurations16. Connecting cells in series increases the overall voltage of the pack while keeping the capacity (in Ampere-hours) constant. For example,串联15个额定电压为3.2V的电芯可以获得总电压为48V的电池组16. Conversely, connecting cells in parallel increases the overall capacity (Ah) while maintaining the voltage of a single cell.并联两个容量为50Ah的电芯可以得到一个总容量为100Ah的模块1. Manufacturers must use cells of the identical type, model, and batch, with capacity, internal resistance, and voltage values differing by no more than 2% to prevent imbalance and premature degradation1. This precise configuration is the first and most critical step in building a safe and efficient pack.

Welding and Assembly Techniques

The electrical interconnection between individual cells is most commonly achieved using advanced laser welding techniques, although ultrasonic welding and pulse welding are also utilized16. Laser welding is often the preferred method for high-volume production due to its excellent reliability, low electrical resistance at the connections, and high-speed operation. The primary disadvantage of this permanent welding method is the extreme difficulty in replacing individual cells should they fail. An alternative method involves using elastic metal contacts, which allow for easier cell replacement but introduce the potential risk of increased resistance and contact failure over time, especially under vibration1. The choice of工艺 is a trade-off between connection reliability, production yield, efficiency, and serviceability.

Interpreting Key Technical Parameters

Understanding a battery PACK's datasheet is essential for proper application. Key parameters include the "Combination Method", such as 1P24S, which denotes 24 cells in series and 1 in parallel, resulting in a nominal voltage of 76.8V for 3.2V cells6. The "Rated Capacity", measured in Ampere-hours (Ah), indicates the total charge the battery can deliver under specified conditions; a 280Ah rating means it can deliver 140A for 2 hours (at a 0.5C discharge rate)1. Finally, the "Rated Energy", measured in kilowatt-hours (kWh), represents the total usable energy storage and is calculated as Rated Capacity (Ah) × Nominal Voltage (V). For instance, a 76.8V, 280Ah pack stores approximately 21.5 kWh of energy6.

Global Market Context and Application Landscapes

The lithium battery PACK market is experiencing explosive growth, deeply intertwined with the global expansion of electric mobility and renewable energy integration.

The global production capacity for动力电池 continues to surge, with 2025 projections reaching a staggering 3,930 GWh7. However, this ambitious expansion leads to a potential market imbalance, as this figure significantly outpaces the anticipated demand of 1,161 GWh for the same year, creating a scenario where supply is nearly 3.4 times greater than immediate needs7. This oversupply underscores a fiercely competitive landscape, particularly outside China. Despite this global capacity build-up, Chinese manufacturers maintain a dominant position, accounting for nearly 70% of the global market share in动力电池装机量7. Industry giants like CATL and BYD continue to lead this charge, with CATL's装机量 reaching 190.9 GWh in the first half of 2025, securing a 37.9% market share7. A key trend is the aggressive overseas expansion of these Chinese firms; while their domestic market share might fluctuate, their international presence is growing robustly, exemplified by Germany becoming the largest export market for Chinese lithium-ion batteries in 20258.

The applications for lithium battery PACKs are diverse and critical for the energy transition:

• Renewable Energy Storage: Battery PACKs are indispensable for stabilizing the intermittent output of solar and wind farms. They store surplus energy generated during peak sun or wind hours and release it during periods of low generation or high demand, effectively solving the problem of intermittency and enhancing grid reliability9. Large-scale projects, like the嘉善县县域储能聚合平台in China, which integrates 174 base stations and user-side storage systems, demonstrate how centralized dispatch of distributed storage resources can ensure regional grid stability and enable precise, orderly power consumption management9.

• Electric Mobility: The electric vehicle (EV) sector is the largest consumer of high-performance battery PACKs. The technology is evolving rapidly towards higher energy densities for longer range and faster charging capabilities. China's momentum in this sector is clear, with动力电池装车量reaching 299.6 GWh in the first half of 2025, a remarkable 47.3% year-on-year increase3. Within this, Lithium Iron Phosphate (LFP) chemistry has solidified its dominance due to its cost and safety advantages, accounting for 81.4% of total装车量in China during this period3.

• Industrial and Residential Backup Power: From providing uninterrupted power for critical data centers to enabling energy independence for households, battery PACKs are a key enabling technology. Industrial backup systems ensure business continuity, while residential systems allow homeowners to store solar energy for use at night or during grid outages, reducing electricity costs and increasing self-sufficiency9. Projects like China Tower's extensive network, leveraging 2.1 million sites to create a distributed energy system providing over 2 million daily battery swaps for logistics workers, highlight the scale and utility of these applications9.

Safety Performance and International Standards

Safety remains the paramount concern in lithium battery PACK design, and significant engineering efforts are dedicated to mitigating risks like thermal runaway.

The choice of cell chemistry fundamentally impacts the safety profile of a PACK. Lithium Iron Phosphate (LFP) batteries are widely recognized for their superior inherent safety compared to Nickel-Cobalt-Manganese (NCM) ternary lithium batteries5. This intrinsic safety advantage stems from the stable olivine structure of the LFP cathode material, which has a much higher thermal decomposition temperature (500-600°C) compared to the layered structure of NCM cathodes, which can begin breaking down at 200-300°C or even lower for high-nickel formulations5. Crucially, when LFP cells are compromised (e.g., by crushing or penetration), they do not release oxygen, which would fuel a fire. Instead, their decomposition primarily produces non-flammable gases like carbon dioxide5. Visual puncture tests starkly illustrate this difference: an NCM cell typically ignites violently within seconds, while an LFP cell may smoke but generally does not catch fire5.

Beyond chemistry, safety is engineered into the PACK at multiple levels. The BMS serves as the primary guardian, continuously monitoring for abnormalities and instantly implementing protective measures such as cutting off current during overcharge, over-discharge, or short-circuit events16. Furthermore, advanced physical safety features are increasingly adopted. These include polymer-composite current collectors designed to inhibit internal short circuits and thermal runaway containment designs within modules that prevent a single cell's failure from propagating to its neighbors10. International safety standards and certifications, such as UL, IEC, and UN38.3, are mandatory for global trade and deployment. These standards rigorously test for electrical, mechanical, and environmental abuse, ensuring that only packs meeting the highest safety thresholds reach the market.