Epoxy Fiberglass Insulation Sheets for Lithium Battery Packs (FR4 / G10 / 3240)

Application of Epoxy Fiberglass Sheets in Lithium Battery Packs Epoxy fiberglass sheets, commonly known as 3240 epox...

Application of Epoxy Fiberglass Sheets in Lithium Battery Packs

Epoxy fiberglass sheets, commonly known as 3240 epoxy sheet, FR4 sheet, or G10 insulation board, are essential materials in modern lithium battery pack manufacturing. These materials provide excellent electrical insulation, mechanical protection, and structural stability, making them widely used in electric vehicles, energy storage systems, and portable battery packs.

In lithium battery packs, epoxy sheets are mainly used for cell insulation, structural reinforcement, and internal component support, helping improve the safety and durability of the entire battery system.

Types of Epoxy Sheets Used in Battery Packs

According to industrial standards such as GB/T 1303-2009 and NEMA standards, the most commonly used epoxy fiberglass sheets in lithium battery applications include the following types:

3240 Epoxy Sheet

3240 epoxy sheet is one of the most widely used industrial insulation boards. It is manufactured by impregnating alkali-free glass cloth with epoxy resin and hot pressing it into laminated sheets.
It offers reliable electrical insulation and good mechanical strength, making it suitable for general battery insulation structures.

FR4 Epoxy Sheet

FR4 is a flame-retardant epoxy fiberglass laminate with a fire rating of UL94 V-0. It typically has a heat resistance of around 130°C.
Due to its excellent fire resistance, FR4 is commonly used in power battery packs and energy storage batteries where higher fire safety standards are required.

G10 and G11 Epoxy Sheets

G10 epoxy sheet provides high mechanical strength, excellent electrical insulation, and low water absorption, making it suitable for demanding battery pack structures.
G11 is an upgraded version with higher heat resistance, and its continuous working temperature can reach 180°C, making it suitable for high-temperature battery environments.

Key Advantages of Epoxy Sheets in Lithium Battery Systems

Excellent Electrical Insulation

Epoxy fiberglass sheets have very high dielectric strength (typically above 20 kV). This effectively prevents electrical short circuits between adjacent battery cells and conductive components.

Strong Mechanical Protection

Compared with metal materials such as steel or aluminum, epoxy sheets are lighter and less likely to scratch the outer casing of battery cells. This helps reduce the risk of mechanical damage and electrolyte leakage caused by vibration or compression.

Thermal Isolation Capability

Epoxy sheets can act as a thermal barrier inside battery packs, slowing the spread of heat if a cell experiences abnormal temperature rise or thermal runaway. This improves the overall safety of the battery system.

Stable Physical Properties

With very low water absorption, epoxy fiberglass laminates maintain stable electrical insulation performance even in humid or harsh operating environments.

Main Applications of Epoxy Sheets in Lithium Battery Packs

Cell-to-Cell Insulation and Isolation

One of the most important applications of epoxy sheets is insulation between individual battery cells. They are commonly placed between large prismatic cells such as LiFePO4 280Ah cells.

Preventing Short Circuits

During operation or transportation, battery cells may experience vibration or friction. Epoxy sheets act as an insulating barrier to prevent direct contact and electrical short circuits between cell casings.

Preventing Thermal Propagation

If one cell overheats, epoxy sheets help delay the spread of heat to adjacent cells, improving the overall safety of the battery pack.

Typical Thickness

Thin sheets with a thickness of around 0.5 mm are commonly used to achieve both insulation performance and efficient space utilization.

Structural Support and Reinforcement

Epoxy fiberglass boards are widely used as structural components inside battery packs due to their high strength and rigidity.

Bottom Support Plate

Placed at the bottom of the battery module, epoxy sheets support the weight of battery cells and provide a stable installation surface.

End Plates and Side Limiters

In battery packs where cells are compressed together for stability, epoxy boards are used as compression end plates or positioning plates to maintain the alignment of the battery cells.

Typical Thickness

For structural applications, thicker sheets ranging from 1.5 mm to 5 mm are commonly used to provide sufficient impact resistance and mechanical strength.

Busbar Support and Electrical Isolation

Epoxy sheets are often used to fix busbars or act as insulating spacers in battery pack electrical connections.
They prevent metal connectors from contacting unintended conductive parts, ensuring safe current transmission between cells.

Battery Pack Enclosure Protection

In simple battery systems such as electric scooter batteries, epoxy sheets may be cut into structural panels and used directly as protective outer enclosures.
They provide protection against external impacts, vibration, and moisture, improving the durability of the battery pack.

BMS and PCB Mounting

Battery Management Systems (BMS) and protection circuit boards are typically installed above the battery pack. Epoxy materials can be used as support columns, brackets, or mounting plates to ensure reliable electrical isolation and mechanical stability.

Conclusion

Epoxy fiberglass sheets such as 3240, FR4, G10, and G11 play a crucial role in lithium battery pack manufacturing. With their excellent insulation properties, mechanical strength, flame resistance, and thermal stability, they help ensure the safety, reliability, and long-term performance of modern battery systems.

As the global demand for electric vehicles and energy storage systems continues to grow, the importance of high-quality epoxy insulation materials in battery pack design will become increasingly significant.