Medical device battery innovation has seen an immense increase in recent years. Batteries have gotten smaller — think multiple fitting onto a contact lens — and cheaper, not to mention the influx of government investment into advancing the technology. In the last few years alone, the Biden Administration and Department of Energy announced an investment of $2.91 billion into battery advancement, the United Kingdom reported the government was investing over £30 million into the technology, and Canada invested $27 million into the construction of a plant specializing in lithium production, a key part of clean battery production.

“We have seen several new devices in development that are leveraging battery innovations from Integer,” Brian Hohl, manager of product development engineering at Integer, told MD+DI. “We have made significant progress in decreasing the size of our batteries while increasing both energy and power density. We produce batteries in a variety of shapes and sizes that give our customers maximum device design flexibility. Earlier this year, Integer launched our Gen2 CFx battery chemistry, which was developed to enable higher power applications as well as Bluetooth Low Energy (BLE) wireless communication. BLE will enable better connectivity between devices and users. Additionally, there is a lot of work and progress with battery miniaturization at Integer. As a recent example, our R&D team has developed and built a lithium-ion battery small enough to fit several onto a contact lens.”

Battery-driven innovation

The battery boom has allowed for advancements in medical devices like leadless pacemakers, fully implantable cochlear implants, and implantable continuous glucose monitors (CGM).

“In cardiac rhythm management, leadless pacemakers are the latest advancement,” Hohl said. “The device is implanted directly into the heart, avoiding the need for leads and surgical implant into the pectoral cavity. Integer’s CFx batteries enable the shape and size requirements needed to achieve such a device.”

Medtronic’s leadless pacemaker got the next-generation treatment recently when the company announced the FDA approval of its Micra AV2 and Micra VR2 devices, which are comparable in size to that of a multivitamin. The size of the device means that the battery not only needs to be small enough to fit, but also contain significant power and longevity. Its new generation does just that, seeing 40% more battery life compared to its previous generations. The median projected battery life of the new leadless pacemakers is nearly 16 years for AV2 and 17 years for VR2, meaning more than 80% of patients who receive a Micra are projected to only need one device for life, according to Medtronic.

The development of a fully implantable cochlear implant with no external unit is also being investigated, but battery challenges have hindered its innovation until recently. In 2022, Envoy Medical received FDA approval of its Investigational Device Exemption (IDE) application to begin a clinical trial with its fully implanted Acclaim implant. The investigational device uses an implanted rechargeable battery intended to last several days between charges.

“Such applications as [fully implantable] cochlear implants eliminate the need for an external device, enabling users to maintain hearing while sleeping, swimming, bathing, or other scenarios,” he said.

Implantable CGMs are another recent innovation benefiting from battery advancements. Senseonics FDA-approved Eversense E3, its newest generation implantable CGM, is a sensor the size of a small twig that is placed under the skin for up to 6 months to monitor glucose readings in real-time. This is in comparison to replacing an external sensor every week or so like other CGMs. Including previous generations of the device, Eversense has been available in the US since mid-2018 and, since 2020, has been sold by Ascensia Diabetes Care (formerly Bayer) after the companies formed a strategic collaboration.

“Another exciting application is the implantable [CGM],” Hohl told MD+DI. “This device wirelessly communicates with diabetic patients’ smartphones, freeing them from weekly or bi-weekly insertions of a sensor placed under the skin, or the need for an external patch or regular maintenance to monitor glucose levels. These applications are made possible as we continue to develop better battery chemistries and manufacturing technologies to reduce battery size while maintaining or improving battery capacity and performance."

Choosing the right battery chemistry

An important factor when developing battery-operated devices is selecting whether to use a rechargeable or non-rechargeable chemistry, according to Hohl.

“For example, you wouldn’t want to worry about recharging the battery for a lifesaving application such as a pacemaker,” he said. “However, a smaller sized device derived from a rechargeable battery would be preferred for pain management. The amount of power and capacity requirements needed for the device also determines what chemistry to choose and what size battery will be needed. Understanding battery performance over the life of the device is also important.”

Integer uses its proprietary in-house simulation software to accurately predict battery performance under customer usage conditions. This gives the company unique ability to leverage its decades of battery manufacturing and testing knowledge to provide users with simulations that “describe precisely how the battery will perform. This allows us to design and iterate virtually to come up with a battery design that will meet our customers’ needs.”   

Safety concerns and recalls

While battery advancements have undoubtedly led to benefits for patients, there have also been reported safety concerns and recalls. Medtronic’s HeartWare Pump is one such device which was recalled for battery faults. The HeartWare recall was due to an interaction between battery software and an internal component making it unable to power the controller, unable to accept charge from the battery charger, or appear to remain charged when in use. Medtronic saw 1,159 reported complaints, six injuries, and one death related to the issue.

The device itself is no stranger to regulatory issues, having three recalls even after it was discontinued in June 2021.

ICU Medical also recently issued an Urgent Medical Device Correction for its Plum 360, Plum A+, and Plum A+3 Infusion Systems replacement batteries, identifying a manufacturing defect that may substantially diminish how long they can be used to run the system when not plugged into AC power.

To limit possible issues, Hohl said there are several steps that should be taken to ensure safety and reliability of every battery.

“At Integer, we work directly with our customers’ technical teams to ensure there is a firm understanding of the device usage conditions,” he told MD+DI. “We design to an established set of guidelines that account for both design and manufacturing needs. Robust testing is performed to verify safety and performance. Manufacturing processes are qualified and demonstrated to be capable. And a stage gate process ensures all requirements are successfully completed before final transfer to production.”