© Design56 | Dreamstime.com - Lithium batteriesLithium rechargeable batteries achieve some of the highest energy densities available today. Not surprisingly, medtech companies are keen to use lithium batteries in medical devices and benefit from reduced weight or increased battery life.
There are a number of safety implications to choosing these batteries as well as practical business implications.

Safety Regulations

Lithium rechargeable batteries have the potential to overheat and even catch fire. This can occur by overcharging, overloading, as well as by mechanically or environmentally over-stressing. For this reason, medical devices containing rechargeable lithium batteries must confirm to the IEC 62133 standard. This standard defines a number of mechanical, environmental and electrical tests that must be performed in order to ensure a product is safe. Usually, to meet this standard, special protection circuits and mechanical protection features must be employed. Additionally the standard risk management process dictated by the IEC 60601 and IEC 14971 standards should also consider the safety implications of using these batteries.

Lithium rechargeable batteries are considered dangerous goods and therefore there are shipping restrictions. The United Nations has defined the UN 38.3 standard which all battery packs and devices containing lithium batteries must conform to in order to be allowed to ship by air. This can be a bit of a surprise when suddenly you’re forced to send your product by ground transport only. Fortunately, the design features that will enable passing IEC 62133 usually are also effective to allow passing UN 38.3.

Business

Lithium rechargeable batteries don’t come in standard battery packs. It is often surprising that you can’t just buy a standard battery pack that has already passed the regulatory hurdles and can be dropped into a product. Although there are plenty of off-the-shelf raw lithium batteries available, these must be combined with protection circuitry, wired to connectors, and packaged in order to use them in a medical device. This invariably is a custom process, specific to each application. Fortunately there are numerous companies that specialise in the custom packaging of lithium batteries and many are equipped to provide the safety testing services required.

There are great, functional reasons to use Lithium batteries in medical devices. With some knowledge of applicable standards and some forethought, the safety, regulatory and business pitfalls that can be avoided.

Kenneth MacCallum, PEng, is a Principal Engineering Physicist at Starfish Medical. He works on Medical Device Development and loves motors, engines and trains as well as the batteries that power them.

Photo credit: © Design56 | Dreamstime.com – Lithium batteries

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4 responses to “Safety and business implications for lithium batteries in medical devices”

  1. Peter Baillie says:

    Has the solid state lithium battery developed at Oakridge with the LIPON electrolyte advanced? I remember the substrate thickness vis a vis battery thickness was an issue.

  2. I’ve been watching the thin film lithium technology advance. It promises higher energy densities over over conventional lithium batteries. There are a few on the market now, particularly for small IoT and non-implantable medical applications.

  3. Melanie says:

    Dear Kenneth,

    I’m wondering how safe it really is to have a device implantanted to record my heart rhythm… I’m told it has a lithium battery and I’m concerned it might have side effects and might even explode while I’m sunbathing or something! It’ll only be just under the skin beneath my collar bone…
    Your thoughts would be appreciated.
    Thanks,
    Melanie

  4. Mike Camplin says:

    Hello Melanie,

    Apologies for the delay in responding. Your comment was overlooked and just surfaced in our web comment queue. Kenneth is currently away on vacation. In case you are still seeking input on your question, I checked with our team and they provided the following response:

    “We are medical device designers, not doctors, so if you have a specific question about a procedure you should consult with your physician for professional medical advice.

    That said, lithium batteries have been safely used in implants since the 1970s. Hundreds of thousands of active medical implants with lithium batteries are implanted in patients every year. Implantable batteries go through rigorous safety testing where they must survive a range of environmental stresses far exceeding what they encounter when implanted in the body. The battery chemistry for implantable lithium cells is different from that encountered in non-implantable products. Implantable batteries generally require long life, so they have low self-discharge and typically very high internal resistance. This reduces the risk of thermal runaway when shorted.

    Ultimately, the decision to undergo a medical procedure is between you and your physician. If you have concerns about a planned operation, you should discuss them with your doctor.”

    I hope this is useful and wish you the best.

    Sincerely,

    Mike

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