Spacing and structure of grid ribs

Spacing and structure of grid ribs

For the grids of motor vehicle starting, large, medium and small fixed valve-controlled batteries, electric power-assisted vehicles, and energy storage batteries, the transverse ribs of the grid are generally designed by gravity casting, and the adjacent ribs face opposite half ribs, as shown in Figure 1. This is mainly to reduce the weight of the grid and leave more space to accommodate the active material while meeting the functional requirements of the grid. Such a layout can make the conductive spacing of the active material uniform and more reasonable.

Spacing and structure of grid ribs
Figure 1 – Frame structure of horizontal bars and vertical bars of grid

For thinner grids (thickness below 1.2 mm), such as the battery grid for starting, the long direction of the thickness of the transverse rib should be flush with the plane of the grid, that is, b = 1/2 e, which is due to the gravity deflection casting formed in the mold cavity by gravity. If the ribs are very thin, the lead liquid cannot flow and form in the mold cavity, and as a result, the grid cannot be cast, and generally b < 0.6 mm will be difficult to form. The size of α should be considered in combination with the size of b. If the size of b is small, the size of α should be appropriately increased. The reason is that if the size of b is small and the size of α is also small, the rib will be difficult to form, generally (α + b) > 1 mm. Under normal circumstances, the size of α is 0.2 ~ 0.4 mm. The top of the transverse rib should be chamfered. Its function is that when the grid is demolded, it is not easy to hang the sheet. If there is no chamfer, the demoulding difficulty will increase and it is not easy to operate. r is generally 0.3 mm. If the rib is too thin, the angle of the r angle can be appropriately increased to increase the cross-sectional area of the rib and ensure the proper performance of the rib. The size of c is generally between 1.0~1.4 mm, and the appropriate size can be selected according to the situation. There is a wide range of choices for the size of d. Through a lot of experiments and accumulation of experience, it is considered that the spacing of the ribs is d = 4.5 ~ 5.8 mm (center spacing) is appropriate. Generally, reducing the cross-sectional size of the rib will increase the difficulty of production and make it difficult to use. Tests have shown that after the distance increases, it has little effect on the initial capacity of the battery, but has a certain impact on the high-current discharge performance and charging acceptance of the battery. Therefore, the value of d cannot be increased too much.

For thicker grids, suitable for battery backup power, α is controlled at 0.2-0.4 mm, b value is controlled at > 0.7 mm, c value is at 1.0~1.4 mm, d value is at 5~7.5 mm, which is more reasonable. One of the parameters can be adjusted according to the specific usage.

The vertical bars of the grid are generally made of whole bars (that is, two complete half bars), the cross-sectional area is about 40% larger than that of the horizontal bars, and the spacing is 12~18 mm.

The rib structure of the mesh grid is determined by the design and equipment, and the size of the grid is determined by the design, and then the corresponding reaming tool is manufactured to form the size of the hole. The thickness of the rib is partly determined by the thickness of the lead tape, and partly determined by the slope of the matrix during hole reaming. The upper and lower borders are left by design. Most battery factories put forward the requirements for grids, and the equipment factory manufactures tooling molds to produce grids that meet the requirements. At present, the battery factory does not have the ability to manufacture tooling and molds for complex equipment such as netting machines.

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