Button battery testing fixtureThe electrical connection stability is the core element to ensure the accuracy and reliability of test data, especially in environments such as high temperature, high voltage, and high humidity. Its design needs to meet the requirements of low contact resistance, strong anti-interference ability, and good long-term stability. The electrical connection stability is elaborated in detail from five aspects: connection method, material selection, structural design, environmental adaptability, and testing verification
1、 Connection method: Ensure low contact resistance and high reliability
Spring compression connection
Principle: Apply constant pressure to the battery electrodes through ceramic springs or metal springs (such as gold-plated beryllium copper) to ensure that the electrodes are in close contact with the fixture contacts.
Advantage:
Adaptive compensation: The spring automatically adjusts pressure when temperature changes or vibrations occur, compensates for differences in material thermal expansion coefficients, and maintains contact stability.
Low contact resistance: Uniform pressure distribution can reduce local hotspots, lower contact resistance (usually<1m Ω), and minimize energy loss and heat generation.
Application: The fixtures of Guangzhou Hezhiyuan Hydrogen Energy Technology adopt ceramic spring sealing, while achieving electrical connection and gas sealing, suitable for high temperature testing at 700-900 ℃.
Threaded locking connection
Principle: Tighten the electrode and fixture contacts through a threaded structure, and fix the connection using mechanical friction.
Advantage:
High seismic resistance: suitable for testing scenarios with vibration or frequent movement (such as in vehicle fuel cell testing).
Adjustable pressure: Control contact pressure by tightening force, suitable for batteries of different thicknesses.
Limitations: Regular check of thread tightness is required to prevent looseness from increasing contact resistance.
Plug in connection
Principle: Using standardized interfaces (such as banana plugs and pin connectors) to achieve fast insertion and removal.
Advantage:
Easy to operate: suitable for high-frequency testing (such as batch production quality inspection).
Modular design: supports multi-channel parallel testing to improve efficiency.
Improvement: Some fixtures have added gold plating or elastic contacts at the plug-in interface to enhance oxidation resistance and contact stability.
2、 Material selection: corrosion-resistant, low resistance, high temperature resistant
Contact material
Gold plated copper alloy: The gold layer (thickness ≥ 1 μ m) can prevent oxidation, and the copper substrate provides high conductivity (conductivity ≈ 58MS/m), suitable for medium and low temperature testing (<300 ℃).
Platinum group metals (Pt, Ir): They maintain chemical stability at high temperatures (>800 ℃), but are costly and are typically used for critical contacts or environmental testing.
Ceramic composite materials: such as aluminum oxide ceramic matrix embedded with metal particles (such as Ag Pd), balancing insulation and conductivity, suitable for high-temperature gas sealing scenarios.
Spring material
Ceramic springs: Zirconia or alumina ceramic springs do not creep or oxidize at high temperatures, and have better pressure stability than metal springs, but they are more expensive.
Gold plated beryllium copper spring: Beryllium copper (CuBe2) has high elastic modulus and fatigue resistance. The gold plating layer can prevent oxidation and is suitable for medium and high temperature testing (300-600 ℃).
insulating material
Polyimide (PI): With a temperature resistance of up to 300 ℃ and high dielectric strength, it is used as an insulation layer for low-temperature fixtures.
Alumina ceramics: resistant to temperatures>1000 ℃, used as insulation brackets for high-temperature fixtures to prevent short circuits.
3、 Structural design: Optimize current path and heat dissipation
Four terminal method (Kelvin connection)
Principle: Separate the current lead from the voltage lead to eliminate the influence of lead resistance on voltage measurement.
Application: Design two sets of independent contacts in the fixture, one for current flow and the other for voltage measurement, to ensure impedance measurement accuracy (e.g.<0.1 μ Ω).
Symmetrical layout
Principle: Symmetrically distribute the battery electrodes and fixture contacts to make the current path uniform and reduce local overheating.
Effect: Under 1A current, the uniformity of temperature distribution can be improved by 30%, reducing the risk of contact resistance drift.
Design of heat dissipation channel
Principle: Insert copper or aluminum heat sinks into the fixture, or use a hollow structure to introduce cooling gas (such as nitrogen) to accelerate heat dissipation.
Data: Heat dissipation design can reduce contact temperature by 50-100 ℃ and extend material life.
4、 Environmental adaptability: anti vibration, corrosion-resistant, anti-interference
Anti vibration design
Measures: Add rubber shock absorbers around the contact points, or use a composite structure of threaded locking and spring compression to absorb vibration energy.
Test: Simulate 10-2000Hz frequency vibration through a vibration table to verify that the change in contact resistance is less than 5%.
Corrosion resistance protection
Measures: Apply a three proof coating (moisture-proof, anti salt spray, anti mold) to the metal contacts, or use a fully ceramic structure to prevent metal corrosion.
Standard: Complies with the requirements of IEC 60068-2-11 (salt spray test) and IEC 60068-2-30 (wet heat test).
electromagnetic shielding
Measures: Use a metal shielding layer on the fixture shell or double twisted shielding on the signal line to reduce external electromagnetic interference (such as 50Hz power frequency interference).
Effect: The signal-to-noise ratio (SNR) can be improved by 20-30dB, ensuring accurate acquisition of microvolt level voltage signals.
5、 Test validation: Quantitative stability indicators
Contact resistance test
Method: Use a micro ohmmeter (such as Fluke 8846A) to measure the resistance between contacts, cycle the test 100 times within the range of -40 ℃ to 800 ℃, and record the resistance change rate.
Standard: A resistance change rate of<10% is considered qualified, and high-quality fixtures can be controlled within<3%.
High temperature aging test
Method: Place the fixture in a high-temperature furnace and run it continuously for 1000 hours at 800 ℃. Regularly check the contact resistance and insulation resistance.
Data: The contact resistance of high-quality fixtures increases by less than 0.5m Ω, and the insulation resistance exceeds 1G Ω.
Vibration and impact testing
Method: Random vibration (5-2000Hz, 5g RMS) and mechanical shock (50g, 11ms half sine wave) tests were conducted according to MIL-STD-810G standard to verify the reliability of the connection.
6、 Typical Case Analysis
Guangzhou Hezhiyuan Hydrogen Energy Technology Fixtures
Electrical connection design: ceramic spring crimping+four terminal method is adopted, and the contact material is gold-plated alumina ceramic composite material.
Stability data: After continuous testing at 800 ℃ for 500 hours, the contact resistance remained stable within 0.2m Ω, and the voltage measurement error was less than 0.1%.
Swiss Fiaxell Open Flanges ™ fixture
Electrical connection design: Threaded locking connection, contact material is platinum iridium alloy, supporting 0-100kg pressure adjustment.
Stability data: After 200 cycles of testing at 1000 ℃, the contact resistance change rate is less than 2%, which is suitable for environmental research.