Eyewear Battery PCM Thermal Buffer for Cold-Weather Runtime

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Solution Overview

Problem

The efficiency of batteries in portable eyewear devices, such as smart glasses, decreases as ambient temperature drops, leading to reduced energy extraction and shorter operating times.

Innovation Solution

Incorporating a phase change material (PCM) around the battery to transfer latent energy and maintain the battery's temperature as ambient temperature decreases, thereby enhancing energy extraction efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If the battery operates in cold ambient conditions, then the battery temperature decreases, but the energy extraction efficiency decreases

Engineering Contradiction:

Improvebattery temperatureVSAvoidenergy extraction efficiency

Core Design Contradiction:

TemperatureVSUse of energy by moving object

Solution Approach 1:

The patent utilizes the phase transition (melting/freezing) of phase change material as the core mechanism. When the battery temperature drops below the PCM's freezing point, the PCM transitions from solid to liquid phase, absorbing latent heat from the surrounding environment and transferring it to the battery, thereby maintaining the battery temperature and ensuring consistent energy extraction efficiency across varying ambient conditions.

Inventive Principle:

Principle #36Phase transitions

Solution Approach 2:

The patent changes the thermal parameters of the battery system by introducing a PCM with specific phase transition temperature and latent heat properties. This parameter change enables the system to actively regulate battery temperature through the PCM's phase transition, counteracting the negative effects of cold ambient conditions on battery performance.

Inventive Principle:

Principle #35Parameter changes

2Temperature

If the ambient temperature drops, then the battery temperature decreases, but the operating time decreases

Engineering Contradiction:

Improvebattery temperatureVSAvoidoperating time

Core Design Contradiction:

TemperatureVSDuration of action of moving object

Solution Approach 1:

The PCM's phase transition provides a sustained thermal buffer that extends battery operating time in cold conditions. As the PCM melts, it continuously supplies latent heat to the battery, delaying the point at which the battery temperature drops to levels that significantly reduce capacity and operating time.

Inventive Principle:

Principle #36Phase transitions

Solution Approach 2:

The PCM is pre-positioned around the battery and pre-charged to the appropriate temperature range before use. This preliminary preparation ensures that when cold ambient conditions occur, the PCM is already in position and ready to immediately begin transferring latent heat to the battery, preventing temperature drop and maintaining operating time.

Inventive Principle:

Principle #10Preliminary action

3Temperature

If the ambient temperature decreases, then the battery temperature decreases, but the energy extraction decreases

Engineering Contradiction:

Improvebattery temperatureVSAvoidenergy extraction

Core Design Contradiction:

TemperatureVSLoss of energy

Solution Approach 1:

The PCM's phase transition creates a thermal buffer that prevents excessive heat loss from the battery to the cold environment. By maintaining the battery temperature through latent heat transfer, the system reduces the temperature gradient between battery and environment, thereby minimizing parasitic heat loss and maximizing usable energy extraction.

Inventive Principle:

Principle #36Phase transitions

Solution Approach 2:

The patent converts the harmful effect of cold ambient temperature into a beneficial thermal regulation mechanism. The PCM utilizes the temperature difference between the cold environment and the battery to drive its phase transition, which in turn transfers heat to the battery, effectively using the cold environment's thermal energy to maintain battery temperature and improve energy extraction.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 PCM helps maintain the battery's temperature, ensuring consistent energy extraction and extended operating times even in cold ambient conditions.

Implementation Method 1

a phase change material (PCM) is positioned about a battery such that a latent energy of the PCM transfers to the battery as the ambient temperature drops to maintain a battery temperature

Methodology Applied

Scientific EffectPhase change: Phase Change

Implementation Method 2

the latent energy maintains the temperature of the battery until the PCM loses it latent energy and converts to a solid phase

Methodology Applied

Scientific EffectLatent energy transfer: Latent Heat

Data Source

PatentUS12237486B2Eyewear device battery with phase change material for temperature regulation

Publication Date: 2025.02.25 SNAP INC

AI summary

A phase change material (PCM) is positioned about a battery of an eyewear device such that a latent energy of the PCM transfers to the battery as the ambient temperature drops to maintain a battery temperature. The latent energy maintains the temperature of the battery until the PCM loses it latent energy and converts to a solid phase. At normal operating temperatures, the PCM is in the liquid phase.