リチウム電池パックの組み立て工程に潜入：精度、性能、パワー

パワフルでコンパクト、そして信頼性の高いバッテリーパックの背後には、高度に管理された精密な製造工程があります。この記事では、リチウム・バッテリー・パックがどのように組み立てられるのか、セルの選択から最終試験、梱包までの各工程に焦点を当てながら、包括的な概要をご紹介します。

Battery Cell Selection

The battery pack assembly process starts with the selection of lithium cells. The three most common types of lithium-ion cells used are:

Cylindrical Cells (e.g., 18650, 21700)

Prismatic Cells

Pouch Cells

Each cell type offers different benefits in terms of energy density, thermal management, and structural integration. Cell selection is based on the application — for instance, high-power EVs may use 21700 cylindrical cells, while space-constrained devices may prefer prismatic or pouch types.

Key Considerations:

Voltage and capacity ratings

Internal resistance

Consistency in performance (matched cells)

Manufacturer reliability and safety certifications

Before assembly, cells undergo quality testing to ensure uniform performance. Disparities in voltage, internal resistance, or capacity can lead to inefficiency and safety risks.

Cell Grading and Sorting

Once the cells are selected, they are sorted or graded. This step ensures that only cells with similar electrical characteristics are grouped together in a battery pack, optimizing performance and safety.

Sorting Criteria:

Voltage range

Internal resistance

Capacity (mAh or Ah)

Manufacturing date and batch

Automated equipment often conducts this process, using advanced algorithms and robotic arms to handle high volumes of cells accurately.

Battery Pack Design and Configuration

Design is critical to ensure the battery pack meets the application’s requirements for power, voltage, current, size, weight, and thermal management.

Common configurations:

Series Connection (S): Increases the voltage

Parallel Connection (P): Increases the current/capacity

For example, a 13S4P configuration implies 13 cells in series and 4 in parallel. Engineers use simulation software to determine the most efficient and safe design.

Mechanical Structure:

Cell holders and brackets

Insulation layers

Impact-resistant casing

Thermal management channels

Cell Spot Welding and Interconnection

Once the layout is confirmed, cells are fixed in position and electrically connected using nickel strips or copper conductors.

Spot Welding Process:

Nickel strips are placed over the cell terminals

A high-current pulse creates localized heat, welding the strip to the cell

The weld must be strong, conductive, and clean

Laser welding is also gaining popularity for its precision and reduced thermal impact.

Battery Management System (BMS) Integration

The Battery Management System (BMS) is a critical component that monitors and controls the battery pack’s operation.

Functions of BMS:

Monitoring voltage, temperature, and current

Balancing charge across cells

Providing protection against overcharge, over-discharge, overcurrent, and short circuits

Communicating with external systems (CAN Bus or UART)

Wiring harnesses connect the BMS to each series of cells to ensure accurate monitoring. The BMS board is typically attached to the top or side of the battery pack.

Insulation and Thermal Management

Safety is paramount in battery pack design. Proper insulation materials and heat-dissipation systems are essential to prevent thermal runaway and short circuits.

Insulation Techniques:

Kapton or fish paper between cells

Heat shrink tubing around pack

Foam padding for shock absorption

Thermal Solutions:

Air cooling channels

Heat sinks or aluminum plates

Phase-change materials or liquid cooling (for high-performance applications)

Enclosure and Mechanical Assembly

The assembled cells, wiring, and BMS are enclosed in a protective casing to shield the pack from physical damage, moisture, and dust.

Case Types:

Plastic injection-molded enclosures

Aluminum alloy casings

Custom 3D-printed holders (for small-scale production)

The casing is sealed, often with ultrasonic welding or industrial adhesives, and sometimes includes vents or pressure release valves for safety.

Testing and Quality Control

Every lithium battery pack undergoes rigorous testing before shipment.

Electrical Tests:

Voltage and capacity verification

Charge/discharge cycle testing

Load and impedance checks

Safety Tests:

短絡保護

Overvoltage and undervoltage response

Temperature rise under load

Visual Inspection:

Spot weld integrity

Connector alignment

Casing defects

Many manufacturers use automated testing stations to ensure consistency and traceability.

Labeling and Compliance

To meet international safety and transport regulations, battery packs must be labeled appropriately. This includes:

Rated voltage and capacity

Manufacturer name and contact info

Compliance marks (e.g., CE, UL, UN38.3)

QR codes or barcodes for traceability

UN38.3 testing is especially crucial for batteries intended for air shipment.

Packaging and Logistics

The final step is packaging the battery for shipping. Anti-static bags, foam inserts, and sturdy cartons are used to prevent physical or electrostatic damage.

Some shipments require:

Dangerous goods declaration

Special labeling (e.g., “Lithium Battery Inside”)

Custom documentation for customs clearance

Trends and Innovations in Battery Pack Assembly

The battery industry is evolving rapidly, with automation, AI, and sustainability driving the next generation of pack production.

The assembly of lithium battery packs is a highly technical and quality-sensitive process. From cell selection and configuration to BMS integration and safety testing, each step plays a vital role in ensuring the final product is safe, durable, and high-performing.