By Sean Fenske, Editor-in-Chief

As more medical devices and their components grow smaller, interest in moving these devices closer to the area of concern increases. That is, the opportunity to leverage implantable medical devices has grown significantly as the necessary therapies can be provided through them. As such, the right parts must be identified to fabricate these miniature medtech solutions.

While every element of the device is important, few are as significant as the power source that drives the technology. Batteries are most commonly used for this purpose, but they come with a variety of considerations designers need to keep in mind. With this in mind, it’s critical medical device companies work with power supply experts well-versed in the incorporation of implantable batteries.

To help explain the important aspects of implantable batteries and, more specifically, off-the-shelf (OTS) options, Gregg Bruce, Senior Technical Fellow at Resonetics, responded to several questions. In the following Q&A, he provides insights on application areas, the advantages of OTS batteries, potential challenges, and often overlooked factors.

Sean Fenske: Given the increasing amount of electronics in medical devices, how much growth are you seeing in the demand for medical batteries?

Gregg Bruce: The bioelectronic sector is experiencing rapid growth, and Resonetics is well-positioned to capitalize on this momentum. While cardiac monitoring and cardiac assist devices remain more mature markets, we’re seeing spectacular expansion in the neuromodulation and brain-computer interface sectors, where much of the innovation in bioelectronics is currently taking place. Our tailored services and product offerings support innovative companies looking to accelerate their path to market.

Fenske: What advantages do off-the-shelf battery solutions offer versus custom batteries?

Bruce: Off-the-shelf batteries offer several key advantages that make them a smart choice for medical device OEMs.

• There are no development costs or development time
• Less expensive, faster, and eliminates technical risk
• Lead times are shorter—weeks as opposed to months or years
• Stock is readily available
• Performance characteristics are known; therefore, Resonetics can test a customer’s device protocol to confirm battery capability

These are key advantages for companies developing cutting-edge device therapies. Not only will OTS batteries from Resonetics free up funding to focus on other aspects of the device, but they will also remove the battery from the critical path, helping teams reach their next funding milestones more quickly.

Fenske: Is the size of the battery a concern for device makers?

Bruce: Yes, battery size is one of the biggest concerns for medical device companies. The reduction in the size of electronics has advanced much more rapidly than improvements in energy density (Wh/L or watt-hours per liter) for batteries. Size truly matters, especially in the implantable space where every component that goes inside the body must be as small and efficient as possible. Much of the innovation in this field is driven by the need to minimize size without compromising performance. Do they struggle to find a balance between battery size versus power needs? Yes, especially when it comes to primary or single-use batteries. This challenge is less significant for secondary or rechargeable batteries, since lithium-ion technology is inherently designed for high-rate performance. There is always a tradeoff, and we continuously work on increasing capacity density. At the end of the day, it comes down to a design decision between size and capacity, and determining what best fits the specific application.

Fenske: What challenges beyond size are associated with medical batteries, and how does Resonetics address these?

Bruce: As a result of advances and improvements in electronics, lower power demands, miniaturization, and the ability to download data via Bluetooth, the demands on the power source have driven the battery design in conflicting directions, especially for the non-rechargeable cells. As overall energy demand decreases, battery size can be reduced. However, the introduction of Bluetooth communication raises power requirements. Lower energy consumption and higher power needs are often at odds, making this a true balancing act.

An alternative approach to reducing energy demand is to extend device longevity, with battery lifetimes now measured in decades. To demonstrate performance beyond 10 years, accelerated testing at elevated temperatures is required. The effects of calendar life become increasingly important, and calendar life losses must be accounted for.

Fenske: Does Resonetics offer complementary services around the battery, such as assembly, design, prototyping, or other value-added offerings?

Bruce: Yes, Resonetics offers a full range of complementary services that extend well beyond the battery itself. Our vertically integrated capabilities allow us to support customers from early design through full-scale production. Our AGILE Product Development® team and LightSpeed Labs® partner with customers on concept development, rapid prototyping, and performance testing to accelerate design cycles and reduce time to market.

In addition, we provide advanced laser machining, welding, and cutting of components used in implantable and interventional devices. This expertise ensures custom welded connections to the battery terminals are produced to exact specifications, maintaining reliability and biocompatibility.

For rechargeable batteries, our teams can guide customers on optimizing electrical performance through charge and discharge parameters to meet specific requirements. Resonetics’ core competency also includes thousands of battery test stations integrated with 37°C thermal chambers, enabling evaluation under customer-specific protocols to support regulatory submissions.

With more than three decades of experience in implantable-grade batteries, Resonetics provides customers with access to a comprehensive library of technical reports and position papers that can be incorporated into their Design History File. Across all divisions, we work as an extension of the customer’s team, combining our deep materials knowledge, design capabilities, and manufacturing precision to help bring next-generation medical devices to life.

Fenske: When it comes to needing a battery for a medical device, what is commonly overlooked or neglected to be considered when selecting the right option?

Bruce: Battery performance is not guaranteed. If mishandled or not used correctly, the battery will not deliver the expected performance, especially over prolonged use. Resonetics will review the customer’s specification and select the best cell chemistry, primary or secondary, and provide guidance on how to use the cell, with emphasis on discharge and charge conditions.

One issue that has emerged is the selection of an end-of-discharge voltage that is set too high for a non-rechargeable cell.

The customer should not assume the electronics can compensate for high discharge rates.

Fenske: Do you have any additional comments you’d like to share based on any of the topics we discussed or something you’d like to tell medical device manufacturers?

Bruce: A battery is a live manufactured part; how it performs depends on how it has been treated during its lifetime. Batteries should be treated as the most critical part of a device and used in a benign manner to ensure performance for the full lifetime of the device.

The battery should be selected first and the device designed around the battery. Design the device to keep heat sources away from the battery to ensure long battery life. At Resonetics, we have a long-standing history in implantable battery development. Our team guides customers through every stage of battery selection, including regulatory requirements, proper battery management, health monitoring during use, and the creation of criteria and decision trees to be integrated into device firmware. Our goal is to help customers develop devices that deliver the highest levels of performance, reliability, and safety.

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