PACK manufacturing process series: Battery Pack Module Assembly and Strapping Solutions(module box, PET plastic steel belt, steel belt, welding, CTP bonding)

As the battery pack industry continues to pursue increased energy density, the way battery cells are grouped and fixed into modules has also been changing, from CTM to CTP.

The bundling and securing of battery modules not only affects the structural stability of the modules, but also requires consideration of the cell expansion force (which affects cycle life). Furthermore, the module packaging method sometimes needs to consider ease of disassembly.

(1) Module box solution

Grouping method: Encapsulating the battery cells, structural components (such as end plates and side plates), and functional modules (such as the cooling system) within a casing to form independent units, thereby creating standardized modules.

Features: Early battery packs mostly adopted the CTM solution. Due to poor cell consistency, the battery pack design was conservative and had many structural parts. The use of plastic module boxes to secure the cells provides higher reliability.

This solution is mostly used in cylindrical battery modules, which facilitates quick assembly.

(2) PET plastic steel belt solution

Grouping method: Use PET plastic steel belts to fix the battery modules through hot welding buckles or mechanical locking.

Features: The plastic-steel belt is light in weight, which is conducive to the lightweighting of the battery pack; the plastic-steel belt is acid- and alkali-resistant and anti-oxidation, and can be used in the complex environment inside the battery pack.

Operation method: One-button operation of the electric baler .

Disadvantages: Its tensile strength is much lower than that of steel strips, so it is usually used in conjunction with steel strips. For example, with an upper steel strip and a lower PET plastic steel strip, the upper steel strip effectively limits the longitudinal expansion and deformation of the module, while the lower PET plastic steel strip can flexibly adapt to fluctuations in battery cell dimensional tolerances.

(3) Steel belt solution

Grouping method: Use stainless steel or galvanized steel strips (pre-welded) to fix the modules. Generally, the steel strips need to be insulated and heat-insulated with heat shrink tubing or mica.

Features: The steel belt has high tensile strength, excellent fire resistance, and is easy to install, which helps to speed up production.

Disadvantages: The steel strip has poor adaptability to fluctuations in battery cell size tolerances.

(4) Riveting solution

(5) Side plate and end plate welding solution

Group method: Use industrial robots to perform laser welding or CMT welding to connect the side panels and end panels.

Features: The number of connecting parts is reduced and the structure is reliable .

(6) Bolt connection solution between end plate and side plate

(7) CTP (Cell-to-Pack) structural adhesive bonding solution

Grouping method: Use high-strength structural adhesive (such as polyurethane, epoxy adhesive) to directly bond the battery cell and the shell, eliminating mechanical connection.

Lightweight : Reduce metal connectors and improve volume utilization .

Thermally conductive structural adhesive combines two major functions: fixation and heat transfer .

High bonding strength : The structural tensile strength is generally ≥8 MPa, meeting vibration and impact requirements .