电池模组隔板与支架用什么尼龙?阻燃绝缘尺寸稳定耐温

应用领域 发布时间: 2026-09-14 2014 阅读

What type of modified nylon is used for the 156 battery module spacers and brackets?

The role of plastic parts in the module

The modified nylon parts in the battery module include: cell separators and brackets, module end plates and side plates, brackets for the CCS integrated busbar (wiring board), sampling wire grooves and wire clips, and cushioning pad frames between cells.

There are three types of functions: structural support (securing the battery cells), electrical insulation (isolating high voltage), and harness management (securing the sampling lines).

The common requirements are flame retardant, insulating, dimensionally stable, and heat resistant.

On-site Restoration: Redesign of the Bracket Triggered by Module Expansion Deformation

Last March, a battery module factory's mass production line reported: the end-plate brackets of fully charged modules were bulging outward, and after eight hours they returned to normal, causing the positioning pins on the assembly line to start failing to fit.

Upon investigation, it was found that the expansion force of the fully charged battery cells pushed the bracket beyond its elastic deformation, and the modulus of the bracket material further decreased under the full charge temperature rise, causing the deformation to exceed the design margin when combined.

There was an interlude during the discussion of the plan: the structural engineer's first reaction was to thicken the bracket, while the materials engineer pointed out that thickening would make the bracket heavier and take up expansion space. A better approach would be to switch to a high modulus grade and optimize the orientation of the support ribs.

Both sides made a compromise: the bracket was replaced with a fiberglass grade with 40% high rigidity, and the ribs were changed from straight ribs to arch-shaped ribs, which not only resist expansion but also allow the battery cells some breathing space. The improved module passed 200 full-charge cycle expansion tracking tests, with positioning accuracy remaining stable throughout.

This case was written into design textbooks by the module manufacturer, with the chapter title being 'Brackets Aren't Walls'—the task of a bracket is to constrain and guide, not to resist force directly. Similarly, the task of a material is not to be infinitely stiff, but to find the right balance between rigidity, toughness, and dimensional stability.

Flame retardancy is mandatory

All plastic parts within the battery module are required to be UL94 V-0 flame retardant, and the mainstream requirement is halogen-free (the smoke toxicity during battery thermal runaway is a secondary hazard to vehicle occupants).

Pay attention to wall thickness impact — the partitions inside the module are usually very thin (0.8-1.5 mm), and the flame retardant rating decreases for thin walls.

Flame retardant testing must be carried out according to the actual wall thickness; reports using 3.0 mm test pieces cannot be used. This is the most common reason for rework in mold components.

Dimensional stability and assembly

The dimensional accuracy of the cell separator directly affects module assembly and the clamping force of the cell. The moisture absorption and swelling of PA is a risk here (the module requires long-term dimensional stability).

Three coping methods: The first is to use a low water absorption system (mineral filling or PA12);

Second is controlling the humidity within the module (the battery pack is sealed, so the humidity is actually controllable); third is using elastic components in the design to absorb dimensional changes (the cell separators usually have elastic structures).

Temperature-resistant and electrolyte-resistant

The temperature inside the module is usually between -30℃ and 60℃ (normal operation), but during thermal runaway, local temperatures can reach several hundred degrees.

Plastic parts will be burned in thermal runaway—this is acceptable (the role of flame retardant is to slow down the spread, not to stop it).

Also, pay attention to electrolyte compatibility — the electrolyte (carbonate-based lithium salts) leaked from the cell can corrode plastics.

PA has a certain tolerance to carbonates, but verification needs to be done.

The Special Characteristics of CCS Busbar Supports

The CCS (Cell Contact System) integrated busbar bracket is a key plastic component in the module—

It needs to secure the copper busbars and sampling wires, while also providing insulation and flame retardancy. Requirements: flame retardant V-0, CTI ≥ 400V, high dimensional accuracy (the busbar must be precisely aligned), and must withstand welding processes (laser welding or ultrasonic welding for the busbar).

The bracket must be heat-resistant and not deform. This is the plastic part with the highest technical content in the module.

A deeper look: The thermal runaway logic behind mandatory flame retardant requirements

The flame retardancy of plastic parts within the module is mandatory, and the logic should be understood in the context of a thermal runaway scenario. When a cell undergoes thermal runaway, the temperature instantly rises by several hundred degrees. The separators and brackets within the module are the pathways for flames and hot gases, and plastic parts that do not meet the flame retardant standard can become accomplices in the spread.

The industry standard requirement is dual assessment of vertical burning rating plus glowing wire test, and thin-walled partition parts must also pass the needle flame test. These tests are not cheap, but they correspond to the vehicle thermal safety regulations, with no room for negotiation.

The impact of flame-retardant modification on dimensional stability is a challenge for engineering implementation. Flame-retardant fillers reduce the shrinkage rate of injection molding but increase the risk of warping. For parts like module brackets with mounting holes, the hole distance accuracy must be maintained even after aging. The dimensional drift under the combined effects of creep and flame retardancy needs to be verified separately.

The experience of a certain customer is that for bracket-type parts, after being stored at high temperature for 100 hours, the hole spacing is remeasured, and grades with data that do not meet the standard are immediately eliminated. This threshold filtered out 40% of the candidates.

Electrolyte resistance is an additional consideration for ternary battery modules. Cell leakage is a low-probability event, but when leakage occurs, the attack of the electrolyte on plastics must be tolerable. Carbonate-based electrolytes can cause swelling in certain grades, and soaking tests must be conducted using real electrolytes rather than substitute solvents. For lithium iron phosphate system modules, this requirement can be relaxed, but for ternary systems, it must be fully implemented.

Extended Judgment: Implicit Variables of Module Components

There are three hidden variables that are most easily overlooked. The first is the swelling force of the battery cell—battery cells expand during charging and discharging (the swelling force can reach several thousand newtons), and the separator must be able to withstand long-term swelling forces without creeping failure.

Secondly, thermal propagation—the design of the separator should slow down the propagation during thermal runaway; this is part of the safety design, with the material being just one component.

Third is recycling and reuse — when disassembling and recycling battery packs, plastic components should be easy to separate, and material labels should be clear.

Engineering field measurement: 4 mandatory tests

Test 1: Thin-wall flame retardant (1.0 mm). Special halogen-free flame retardant grades reach V-0, while general grades only reach V-2 — must be tested according to the actual wall thickness.

Test 2: Cell expansion force (long-term). PA66-GF30 separator 1000 h creep 0.5%, mineral-filled system 0.2%.

Test 3: Electrolyte compatibility 500 h. PA66 mass change 3.5%, strength retention 78% — acceptable, but needs verification.

Test 4: CTI (CCS bracket). Dedicated system 450V, general flame-retardant system 350V — busbar bracket must be ≥ 400V.

Boundary Declaration

Operating conditionRecommended materials
Battery Cell Separator / BracketHalogen-free flame retardant, low water absorption system
CCS Busbar BracketFlame Retardant V-0 CTI ≥ 400V Welding Heat Resistant
Module end plate / side plateGF30 Reinforced Flame Retardant
Sampling Duct / Cable ClampFlame-retardant PA66
thin-walled partConduct flame retardant tests according to the actual wall thickness

Engineering Memo

All plastic parts in the battery module are required to be V-0 halogen-free flame retardant, and must be tested according to the actual thin wall (0.8-1.5 mm) — using a 3.0 mm test piece report as a replacement is the most common reason for module rework. The CCS busbar bracket has the highest technical content.

Practical Case Study: Common Pitfalls and Correct Solutions

Pitfall 1: Choosing materials based on traditional automotive thinking ignores electrical safety requirements. Correct answer: The primary criterion for plastic parts in new energy vehicles is often electrical performance—CTI (compared to leakage trace index), flame retardant rating, arc resistance. These insignificant indicators in traditional cars are hard thresholds here. Pitfall 2: Only looking at flame retardant rating, ignoring electric marks under long-term damp heat. Correct answer: Flame retardant is behavior during fire, CTI is long-term operation—both are needed. High-voltage parts usually require CTI ≥ 600V and flame retardant V-0; missing one means long-term hidden dangers. Pitfall 3: Simply interpreting battery conditions as "high temperature," ignoring alternating hot and cold and damp heat. Correct answer: The battery pack is a composite environment of temperature alternating + humidity changes + coolant; verify the combination of temperature shock + damp heat + coolant compatibility. These three pitfalls are all must-check checklists before mass production.

Follow-up Three-Link: Three high-frequency questions from mold module readers

First question: Can the partition and bracket be made of the same material? Yes, but it is recommended to use different tiers. The partition is thin-walled and large-area, focusing on flame-retardant and shrink-resistant holes; The bracket is thick-walled with holes, focusing on modulus and creep. Products of the same grade meet both ends, but the price is usually higher than selecting materials separately for tiering; for large-scale mass production, selecting separately is more cost-effective.

Second question: What is special about the CCS busbar bracket? It serves both structural support and electrical insulation, and also requires embedded copper-aluminum busbars. Stress concentration at insert positions and shrinkage after injection are two major challenges. Support materials use low-shrinkage, high-rigidity systems, and insert preheating parameters must be co-calibrated with material suppliers.

Third question: How should the temperature resistance requirements for mold components be determined? Write two lines according to the module's thermal management specifications for short-term thermal runaway endurance. One working temperature level is used for substrate selection, and one short-term thermal runaway level is used to determine flame-retardant and heat-resistant systems; both lines must be supported by data.

Reverse Case: A partition without electrolyte verification

A module factory skipped electrolyte immersion verification to rush the schedule. After mass production, a batch of cells experienced microleakage, and the partition swelled and deformed under the electrolyte's action, causing the cells to be squeezed and triggered a larger alarm. The cost of rework was disassembly and reassembly of the entire batch of modules. A low-probability event does not mean zero; each line on the verification list corresponds to a certain probability.

Addition: Practical questions from three other readers

Fourth question: How much room is left for lightweight mold components? Bracket thinning, integration, and new materials are all moving forward. After integrating brackets and fixing parts, the number of parts decreases, assembly labor time is saved, and the main focus of lightweight design is actually integration, not simply thinning.

Fifth question: How long is the material verification cycle for module factories? Each round of flame retardant and conventional performance takes about eight to ten weeks, while projects including thermal runaway related verification cycle double. The fixed timing should be reversed; the most common reason for module project delays is the slow start of material selection.

Sixth question: What are the differences between the mold components of round cells and prismatic cells? The bracket of the circular cell module must adapt to the curved contact of the cylindrical cylinder, requiring high precision in hole machining; The bracket of the prismatic cell module must withstand greater expansion force and higher rigidity requirements. Modules and components of the two technical routes cannot be interlocked.

On-site observation from a group

Observation One: Most module internal component failures occur during assembly. In cases of bracket brittle cracking, stress concentration is mainly caused by incorrect assembly tightening sequences. Providing explanations of the upper limit of assembly torque on the material side can reduce most of these complaints.

Observation Two: CCS integration makes brackets more complex. The integration of busbars, sampling wiring harnesses, and temperature sensors turns brackets from single structural components into multifunctional carriers, doubling the number of inserts, and the yield of one-step injection molding becomes a new competitive point.

A set of numbers at the end

Number One, regarding cell expansion force. The expansion force of a square cell when fully charged can reach several thousand newtons, and the rigid design of brackets is based on this magnitude. If you don't know the structural design of this number, the drawn-up bracket looks nice on paper, but once the module is installed, it becomes visible.

Number Two, about the cost proportion of flame retardant. Of the material cost of plastic parts inside the module, the flame-retardant system contributes 30% to 50%, making it the largest cost item. Every upgrade in flame retardant grade requires asking about the standard basis, and the more you ask, the more you save money on over-design.

Number Three, about hole spacing accuracy. After aging of mounting hole spacing, the drift requirement is generally within ±0.2 millimeters. Low-shrinkage grade mold flow analysis is the basic basis for compliance. Brackets with excessively different hole spacing cannot be installed; returns and shutdowns all come from this.

Last Word

The unit price of plastic parts inside the module is not high, but it is a link in the thermal safety chain. Flame retardant is not compromised, dimensions do not drift, and resistance to medium is not lucky. If these three are upheld, this part will deserve its position.

Note

Another practical suggestion: before the module bracket is fixed, conduct a round of assembly process evaluation, including tightening tools, sequence, torque limit, and material toughness together. Faults where materials are qualified but assembly is out of control are most likely to be misjudged as material problems during after-sales inspections.

adds a note

If the material supplier for mold modules can provide actual shrinkage rate measurements for each batch with the goods, the module factory assembly line parameter adjustments will have a basis. These small services accumulate to build long-term cooperation.

Conclusion

What material is used for this piece—the earlier you ask about material selection, the easier it is.

For material selection and mold trial for these parts, you can talk about it together

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