The connection terminals of lithium battery packs are key components for achieving electrical connection between battery cells, current transmission and safety protection. Their design needs to comprehensively consider electrical performance, mechanical strength, thermal stability, environmental adaptability and manufacturability. The following are the specific design requirements and implementation paths:

First, electrical performance requirements

Low contact resistance

The contact resistance of the connection terminals should be ≤0.1mΩ (at the rated current) to reduce heat generation and energy loss.

Implementation path

Adopt high-conductivity surface treatments such as gold plating and silver plating to reduce the resistance at the contact interface.

Increase the contact pressure (such as by pre-tightening through spring plates or bolts) to ensure that the contact surfaces are fully in contact.

Case: A certain energy storage battery pack was connected to the cell terminals through laser welding, reducing the contact resistance by 60% compared to the traditional bolt connection and lowering the temperature rise by 15℃.

High current-carrying capacity

The terminals must meet the maximum continuous current (such as 100A-1000A) and instantaneous overload current (such as 3 times the rated current, lasting for 10 seconds) requirements of the battery pack.

Implementation path

Increase the cross-sectional area of the terminals (such as using copper bars with a cross-sectional area of ≥20mm²).

Optimize the terminal shape (such as using a double-layer structure or thickening design) to disperse the current density.

Case: A certain electric vehicle battery pack, through a double-layer copper bar terminal design, has its current-carrying capacity increased to 1200A, and the temperature rise is controlled at ≤50℃.

Resistant to electrochemical corrosion

Requirement: Throughout the entire life cycle of the battery pack (such as 10 years), the terminals must resist corrosion from electrolyte, moisture and salt spray.

Implementation path

Corrosion-resistant materials (such as red copper, nickel-based alloys) and three-proof coatings (such as polyurethane, acrylic) are adopted.

Avoid direct contact between different metals (such as copper and aluminum) to prevent galvanic corrosion.

Case: A certain outdoor energy storage battery pack was treated with nickel plating on the terminal surface and a three-proof coating. After the salt spray test (5% NaCl, 96 hours), the contact resistance change was ≤5%.

Second, mechanical strength requirements

Resistant to vibration and shock

Under vibration conditions (such as 10-500Hz, 5g acceleration) and shock conditions (such as 15g, 11ms semi-sine wave), the terminals must maintain electrical connection and structural integrity.

Implementation path

Add terminal fixing points (such as double-bolt fixing) and anti-loosening designs (such as spring washers, thread adhesives).

Flexible connectors (such as FPC and aluminum wire bonding) are used to replace rigid connections to absorb vibration energy.

Case: The battery pack of a certain unmanned aerial vehicle (UAV) was designed with FPC flexible terminals. After the vibration test (10-500Hz, 10g), the resistance change was ≤0.5%.

Fatigue and creep resistance

Under long-term cycling conditions (such as 1000 charge and discharge cycles), the terminals need to resist contact failure caused by material fatigue and creep.

Implementation path

Select high-strength materials (such as beryllium copper and titanium alloy) and optimize the heat treatment process.

Increase the thickness of the terminals (such as ≥2mm) to reduce stress concentration.

Case: The contact resistance of a certain electric vehicle battery pack changed by no more than 2% after 1,000 cycles through beryllium copper terminals and laser welding technology.

Third, requirements for thermal stability

High-temperature resistance performance

Requirement: In the case of thermal runaway of the battery pack or high-temperature environments (such as 85℃), the terminals must maintain mechanical strength and electrical performance.

Implementation path

High-temperature resistant materials (such as ceramic insulators and polyimide substrates) are adopted.

Optimize the terminal heat dissipation design (such as adding heat dissipation fins and liquid cooling channels).

Case: A certain energy storage battery pack, through ceramic insulated terminals and liquid cooling heat dissipation design, has an insulation resistance of ≥100MΩ after continuous operation at 120℃ for 1000 hours.

Flame retardancy and self-extinguishing

The terminal material must meet the UL94 V-0 flame retardant grade to prevent the spread of thermal runaway.

Implementation path

Select flame-retardant plastics (such as PBT, PC/ABS) or a combination of metal terminals and insulating sleeves.

Apply flame-retardant coatings (such as silicone rubber or ceramicized polyolefin) on the surface of the terminals.

Case: A certain battery pack was tested with flame-retardant PBT terminals and a ceramicized polyolefin coating. In the UL94 V-0 test, the flame was extinguished within 10 seconds without any dripping.

Fourth, requirements for environmental adaptability

Waterproof and dustproof

Under a protection level of IP67 or above, the terminals must be protected from moisture and dust.

Implementation path

Sealing is achieved by using sealing rings (such as silicone or fluororubber) and potting compounds (such as epoxy resin or polyurethane).

Design a labyrinth-style waterproof structure or drainage channel.

Case: A certain outdoor energy storage battery pack was encapsulated with silicone rubber sealing rings and epoxy resin. After the IP68 test (1 meter water depth for 30 days), the insulation resistance was ≥500MΩ.

Resistant to high and low temperatures

Within the temperature range of -40℃ to 85℃, the terminals must maintain stable mechanical and electrical properties.

Implementation path

Select materials with a wide temperature range (such as silicone rubber sealing rings, LCP plastic).

Optimize the terminal structure (such as reducing the stress caused by the difference in thermal expansion coefficients).

Case: The battery pack of a certain polar scientific research equipment is sealed with silicone rubber through LCP terminals. After cyclic testing at -50℃ to 85℃, the contact resistance change is ≤3%.

Fifth, manufacturability requirements

Compatibility of automated production

The terminals must be compatible with automated welding, assembly and inspection processes to enhance production efficiency and consistency.

Implementation path

Design standardized interfaces (such as welding positioning holes and assembly guide grooves).

Adopt tool-free connection technologies (such as crimping and snap-on).

Case: Through the design of laser welding positioning holes for a certain electric vehicle battery pack, the welding yield rate has been increased to 99.5%, and the production cycle has been shortened to 5 seconds per piece.

Maintainability and disassemblability

The terminals should support quick disassembly and replacement to reduce maintenance costs.

Implementation path

Adopt modular design (such as independent terminal modules).

Design fool-proof structures (such as terminal interfaces of different sizes or shapes).

Case: A certain energy storage battery pack, through modular terminal design, has reduced the replacement time of a single terminal to 10 minutes, a reduction of 80% compared to the traditional solution.

Sixth, key points for designing typical application scenarios

Electric vehicle

Requirements: High current carrying capacity, anti-vibration, lightweight.

Design: It adopts double-layer copper bar terminals + laser welding +FPC flexible connection, reducing the weight by 30% compared with the traditional solution.

Case: Through the above design, the current-carrying capacity of a certain electric vehicle battery pack reaches 1200A, and the resistance change after vibration test is ≤0.5%.

drone

Requirements: Compact, lightweight, and impact-resistant.

Design: It adopts FPC flexible terminals and vacuum adsorption fixation, reducing the volume by 50% compared with the traditional solution.

Case: Through the above design, the battery pack of a certain unmanned aerial vehicle has been reduced in weight to 60% of the traditional solution and its impact resistance has been enhanced by 40%.

Energy storage system

Requirements: High protection grade, long service life, and corrosion resistance.

Design: It adopts ceramic insulated terminals, three-proof coating and potting compound sealing, with a service life of over 10 years.

Case: A certain energy storage battery pack, through the above design, showed no performance degradation after salt spray test (96 hours) and high-temperature and high-humidity test (85℃/85%RH, 1000 hours).