Plastic Heat Equalization Elements for Battery Packs

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Solution Overview

Problem

Battery packs for electric devices and vehicles experience uneven cooling due to inner cells having poor contact with the outer housing, leading to inefficiencies and potential overheating, and existing metal heat equalization elements can cause short-circuits and are heavy, making them unsuitable for portable tools.

Innovation Solution

Using lightweight, electrically insulating plastic heat equalization elements with thermal conductivity comparable to battery cells, such as thermoplastic polyolefin or elastomeric materials, that conform better to cell surfaces and fill interstices, eliminating the need for additional insulation and preventing short-circuits by design.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If metal heat equalization elements are used in the interstices between cells, then heat equalization among cells is improved, but weight increases and risk of short-circuits increases

Engineering Contradiction:

Improvetemperature distribution uniformityVSAvoidbattery pack weight

Core Design Contradiction:

TemperatureVSWeight of moving object

Solution Approach 1:

The patent changes the material parameter from metal to plastic, specifically selecting plastic materials with thermal conductivity of 0.3-0.5 W/mK to match the thermal conductivity range of battery cells (0.4-0.5 W/mK). This parameter change maintains heat equalization effectiveness while eliminating the weight penalty of metal materials.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite material strategy by using plastic as the base material and optionally incorporating fillers (mineral or metal particles such as aluminum oxide or aluminum with particle size less than 20 μm) to enhance thermal conductivity. This creates a composite plastic material that achieves optimal thermal performance without the weight of solid metal elements.

Inventive Principle:

Principle #40Composite materials

2Temperature

If metal heat equalization elements are used in the interstices between cells, then heat equalization among cells is improved, but risk of short-circuits increases

Engineering Contradiction:

Improvetemperature distribution uniformityVSAvoidshort-circuit risk

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The patent introduces plastic heat equalization elements as an intermediary material between battery cells. This intermediary serves dual functions: it conducts heat to equalize temperature distribution while simultaneously providing electrical insulation. The plastic material acts as a mediator that transfers thermal energy without conducting electrical current, thus preventing short-circuits between adjacent cells.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Strength

If hard metal heat equalization elements are used, then structural support is improved, but conformity to cell surfaces deteriorates

Engineering Contradiction:

Improvestructural supportVSAvoidconformity to cell surfaces

Core Design Contradiction:

StrengthVSShape

Solution Approach 1:

The patent employs flexible plastic heat equalization elements that can deform and conform to the circumferential surfaces of battery cells. The plastic material's flexibility allows it to adapt to surface irregularities and maintain intimate thermal contact with cells, whereas rigid metal elements would create gaps and reduce heat transfer efficiency.

Inventive Principle:

Principle #30Flexible shells and thin films

4Ease of manufacture

If thermoplastics are used for heat equalization elements, then manufacturing economy and adaptability are improved, but thermal expansion mismatch may occur

Engineering Contradiction:

Improveproduction economyVSAvoidthermal expansion stability

Core Design Contradiction:

Ease of manufactureVSStability of the object's composition

Solution Approach 1:

The patent selects specific thermoplastic materials (polyethylene, polypropylene, polyester) with controlled thermal expansion coefficients and incorporates fillers to adjust the thermal expansion characteristics. By changing the material parameters through filler addition, the patent optimizes both manufacturability and thermal expansion stability to prevent excessive expansion or contraction during battery operation.

Inventive Principle:

Principle #35Parameter changes

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

The plastic heat equalization elements improve heat transfer and distribution, preventing overheating and debalancing while being lighter and less expensive, reducing the risk of short-circuits and enhancing the structural integrity of battery packs for portable devices.

Implementation Method 1

the thermal conductivity of this last substance, with a value of approximately 0.40 to 0.42 W/mK, reaches the range of the maximum internal thermal conductivity of most cells

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

plastics as a rule have a higher coefficient of thermal expansion than metals, so that upon heating of the cells, they expand more markedly and thus conform even better to the cells

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS8945748B2Battery pack

Publication Date: 2015.02.03 ROBERT BOSCH GMBH

AI summary

The invention relates to a battery pack (2) for supplying an electrical appliance or an electromobile, especially a power tool, with power. Said battery pack comprises a plurality of battery cells (4) and at least one heat compensation element (18) interposed between neighboring battery cells (4). The invention is characterized in that the heat compensation element (18) consists of a plastic material.