Kapton® RS All Polyimide Heater Keeps Phone Batteries Warm in Cold Weather 

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High school seniors opt for lightweight, thin profile of Kapton® RS Heater for battery heater project


Background Information 

For a group of 12th grade students at the Twin Valley High School in Elverson, Pennsylvania, the capstone project of their senior year engineering program was the development of a cell phone case that could protect the phone’s battery in cold temperatures.

Inspired by their experiences of phone batteries dying while skiing and snowboarding in extremely cold conditions, the students sought a lightweight, powerful heating solution with a very thin profile. The assignment was part of Project Lead the Way, an educational program that supports engineering studies at elementary and high schools across the United States, aimed at helping students learn problem-solving skills and fostering interest in engineering. 

Leading Edge Materials and Support from DuPont

In develoing the phone battery heater, the students followed a scientific approach: (1) identify the problem, (2) justify the problem, (3) develop and test a solution. They found that lithium ion batteries in smartphones operate optimally between 62° to 72° F (16° to 22° C); when temperatures drop below freezing, performance and battery life can drop by 50%. Seeking a lightweight and efficient heating product that would keep a phone battery operating under conditions of extreme cold, they researched DuPont™ Kapton® RS polyimide film online, and reached out to DuPont.

“The goal of the course is to experience the full engineering design process, from identifying a problem through to developing a working prototype,” said Michael Joy, Technology and Engineering teacher at Twin Valley High School. “Part of that process is reaching out to the experts.”

Engineers at DuPont agreed to provide the students with materials, along with plenty of support and advice. During the project, they held weekly phone calls with the students, sharing expertise and ideas.

Prototype Passes the Test Thanks to Kapton® RS Polyimide Heater

To start, the students created a design for a battery heater composed of DuPont™ Kapton® RS polyimide film, with DuPont conductive and dielectric inks printed on top for the circuitry, and a miniature battery. They built a phone case using 3D printing, and positioned the completed battery heater prototype inside it.  

To determine the ideal temperature setting for the prototype, they placed it in a freezer, and took temperature readings at different power densities to understand the optimal heater design. Knowing that the phone itself would produce some heat while running, they selected 60° F (16° C) for the target temperature. They calculated that this would allow the phone to reach the target temperature between 62° to 72° F (16° to 22° C).

The last step was to test the prototype. Because they were conducting the tests in warm weather, it wasn’t possible to test it under actual winter conditions, so they used a freezer. After 20 minutes in the freezer, when the phone had reached steady-state temperature, the temperature was measured. The resulting battery temperature was approximately 78.8° F (26° C), just slightly above the target range.  Moreover, the battery life showed improvement when compared to another phone using the same battery type, which was not heated.

“What the students found really exciting was the chance to work with professional engineers, who were willing to spend time and help them,” said Michael Joy. “It’s definitely furthered their interest in the field, and solidified it. For many of our students, this is what they really want to do in life – pursue a career in engineering or technology.”

Versatile, Reliable Heating Solution

DuPont™ Kapton® RS conductive polyimide film is used across a wide range of applications, including thermal wraps for trauma patients, wind turbine de-icing, and automotive interior heating. It can be cut into any configuration, the temperature is highly customizable, and it will continue to function even if it is punctured. In addition to heating phone batteries, it’s also ideal for heating batteries in drones flying in cold weather, car batteries – any environment where a battery might be impacted by the cold.