Battery Cell Stack Banding Straps for Compression and Expansion

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Solution Overview

Problem

Existing methods for assembling traction battery packs face challenges in maintaining consistent compression across cell stacks, particularly as battery cells expand over time, which can lead to reduced structural integrity and efficiency.

Innovation Solution

The method involves using banding straps, specifically a first strap arranged within a compression fixture to apply compressive force across the cell stack axis, with free ends connected via friction welding, and a second strap installed transversely to maintain compression, utilizing non-reinforced materials like thermal bonded polyester that gradually relax to accommodate expansion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If rigid banding straps are used to maintain compression on cell stacks, then structural integrity is improved, but the ability to accommodate cell expansion over time deteriorates

Engineering Contradiction:

Improvestructural integrityVSAvoidaccommodation of cell expansion

Core Design Contradiction:

StrengthVSAdaptability or versatility

Solution Approach 1:

The patent applies parameter changes by transitioning from rigid banding straps to flexible straps made of elastomeric materials. This material parameter change enables the straps to dynamically adjust their compression force, maintaining structural integrity while accommodating cell expansion through elastic deformation and stress relaxation mechanisms inherent to elastomeric materials.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent implements dynamics by using flexible banding straps that can dynamically adapt to changing cell stack dimensions. The elastomeric material allows the straps to continuously adjust their mechanical properties, providing ongoing compression force that accommodates expansion while maintaining structural support throughout the battery pack's operational life.

Inventive Principle:

Principle #15Dynamics

2Stability of the object's composition

If compression force is applied to cell stacks, then structural stability is improved, but the risk of damage to battery cells worsens

Engineering Contradiction:

Improvestructural stabilityVSAvoiddamage to battery cells

Core Design Contradiction:

Stability of the object's compositionVSObject-affected harmful factors

Solution Approach 1:

The patent employs flexible shells and thin films by using elastomeric banding straps that conform to the cell stack geometry. These flexible straps distribute compression force uniformly across the cell surfaces, providing structural stability while minimizing localized stress concentrations that could cause cell damage.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The patent applies beforehand cushioning by using elastomeric materials with inherent shock-absorbing properties. The flexible straps act as a cushioning layer between the compression force and the battery cells, protecting against mechanical damage while maintaining the necessary compression for thermal contact and structural stability.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Manufacturing precision

If multiple banding straps are used to maintain compression, then compression consistency is improved, but device complexity worsens

Engineering Contradiction:

Improvecompression consistencyVSAvoidnumber of banding straps

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent applies merging by integrating multiple functional requirements into a single flexible banding strap component. The elastomeric strap simultaneously provides compression force, accommodates expansion, distributes load uniformly, and maintains thermal contact, eliminating the need for multiple separate rigid components and simplifying the overall assembly.

Inventive Principle:

Principle #5Merging (Combining)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach ensures stable and efficient compression of battery cells within the traction battery pack, enhancing structural integrity and accommodating cell expansion, thereby improving the overall performance and longevity of the battery pack.

Implementation Method 1

connecting a first free end portion and a second free end portion of the first banding strap, thereby maintaining the compressive force across the cell stack axis

Methodology Applied

Scientific EffectFriction welding: Friction Welding

Implementation Method 2

the first banding strap includes a non-reinforced material that is configured to gradually relax to release compression as the cell stack expands over time

Methodology Applied

Scientific EffectStress relaxation: Stress Relaxation

Data Source

PatentUS20240079627A1Banding straps for assembling traction battery pack cell stacks

Publication Date: 2024.03.07 FORD GLOBAL TECH LLC

AI summary

Banding straps and associated methods may be used for assembling a cell stack of a traction battery pack. One more banding straps may be arranged about the cell stack for temporarily or permanently applying and maintaining compression across the cell stack. In an exemplary method, a banding strap may be arranged within a compression fixture before positioning a cell stack within the compression fixture and applying a compressive force across a cell stack axis of the cell stack. Free end portions of the banding strap may be connected to maintain the compressive force across the cell stack axis.