Effect of metal on the connector of lithium battery pack

The lithium battery connector on market now is more and more, want to design the connector that accords with functional requirement, choose material is very important, and the foundation that choose material is to want to understand the property of material very much, the noun of material property of connector metal material undertakes explaining below, the hope has help to everybody.

. chemical composition

he metal materials used for connectors are generally alloy materials, rarely used in a single metal material. As the name suggests, alloy is a substance composed of a variety of metals, indicating that it has a variety of chemical elements, such as:

hosphorus bronze: it is composed of copper Cu, tin Sn, phosphorus P, iron Fe, lead Pb, zinc Zn, etc.

rass: copper Cu, iron Fe, lead Pb, zinc Zn and other components, the main component is copper.

tainless steel: made of iron Fe, chromium Cr, nickel Ni, carbon C, silicon Si, manganese Mn, phosphorus P, sulfur S, aluminum Al, cobalt Co, the main component is iron.

hysical properties

. Specific gravity/density

pecific gravity is the relative density of a unit of mass and the same unit of water. The specific gravity of a body reflects the weight of a body per unit volume. The weight of an object is caused by the force of gravity on it.

. The elasticity coefficient (modulus of elasticity)

ffect of elastic coefficient on connector: if the connector terminal requires small displacement deformation, limited down stroke and good contact, the material with high elastic coefficient should be selected.

. The conductivity (electrical conductivity) issued

onductivity is the ability of a substance to transmit electric current and is the inverse of its resistivity. The effect of conductivity on connectors: if connectors require low contact resistance, choose materials with relatively high conductivity.

. Coefficient of thermal expansion

t refers to the law coefficient of geometric properties changing with temperature under the effect of thermal expansion and cold contraction. In practical application, there are two main thermal expansion coefficients: linear thermal expansion coefficient and volume thermal expansion coefficient.

. Heat transfer coefficient (Thermal conductivity)

he unit is W/(m.k). A higher value indicates faster heat transfer. And the composition of the material structure, density, moisture content, temperature and other factors.

aterials with high thermal conductivity will lose heat faster and vice versa, but will have a lower temperature rise. Rapid temperature creep is not the desired result of connector use. Copper alloy is a metal material with high thermal conductivity, so it is especially important to pay attention to the material parameter when it is used for battery pack connector in high temperature environment.

echanicalProperties

(1) YieldStrength

Also known as yield strength, is the critical stress value of material yield. The so-called yield, refers to the metal from the elastic state of non-uniform to the elastic-plastic state after a certain amount of deformation stress, it marks the beginning of the macro plastic deformation.

Effect of yield strength on connector: the higher the yield strength of metal material, the greater the positive force of terminal.

2. TensileStrength

When the material yields to a certain extent, due to the rearrangement of internal grains, its resistance to deformation increases again. At this time, although the deformation develops rapidly, it can only increase with the increase of stress until the maximum stress is reached. After that, the resistance of the material to deformation was significantly reduced, and a large plastic deformation occurred at the weakest point, where the section of the specimen was rapidly reduced and the necking phenomenon occurred until the fracture failure. The maximum stress value (corresponding to point b) before tensile fracture of the material is called strength limit or tensile strength.

ElongationPercent

The percentage of the elongation of a metal material to its original length when it is broken by an external force (tensile force).

4. The Hardness (Hardness)

The ability of a material to partially resist hard material being pressed into its surface is called hardness. The local resistance of solids to the invasion of external objects is an index to compare the hardness and softness of various materials. As all metal material of the connector is extremely thin, it is measured by vickers hardness (HV). Vickers hardness (HV) to 120 kg load and apex Angle of 136 ° diamond square forcer pressure cone into the surface of materials, materials of the indentation indentation surface area divided by load values, i.e., for the vickers hardness (HV) values.

Hardness is an important parameter of connector material selection.

5. The R/T ratio

(R (radius) refers to the thickness of a bent inner diameter, and T (thickness) refers to the thickness of the material.)

If you want to shape a product with a smaller inside diameter, you must choose a material with a smaller R/T ratio. Theoretically speaking, if R/T ratio is equal to zero, it means that the bending performance of this material is excellent. Even if R=0 inside the bending, no cracks will occur. However, the general material material proof or property table shows the data of 90-degree bending, and rarely shows the data of 180-degree bending. Of course, we want the R/T ratio to be as small as possible, which is good for miniaturization of battery connector products.

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