When engineers evaluate a battery,听it’s听natural to focus on day-one performance. Higher capacity, strong power output, and impressive energy density can make a battery look like the obvious choice.听

But for implantable medical devices, the most important performance benchmark听isn’t听the first day.听It’s听the last.听

A battery may spend years powering听a听neuromodulation device,听cardiac monitor, or drug delivery device inside听a听patient鈥檚听body. During that time, clinicians and patients depend on it to perform reliably and predictably. Unlike consumer electronics, where a degrading battery can often be recharged more听frequently听or replaced, an implantable device may require an听additional听surgical procedure when its battery reaches the end of its useful life.听

That makes battery longevity a critical consideration. A battery must not only deliver the required performance when听new, but听continue providing the energy and power needed to support therapy, monitoring, or diagnostics throughout its intended service life.听

If battery performance declines sooner than expected, the consequences may extend far beyond an engineering concern. It can affect patient health, disrupt therapy, and lead to an听additional听surgical procedure for device replacement.听

The key question听isn’t听simply, “How much energy does this battery provide when it’s new?”听

It’s, “How much usable energy will remain years from now?”听

Understanding that requires looking beyond capacity and day-one specifications to how the battery performs over time.

 

Longevity Means Different Things for Different Battery Chemistries听

Not all implantable batteries age in the same way.听

For rechargeable implantable batteries听utilizing听Lithium-Ion chemistry, longevity is typically measured by how well the battery听maintains听its capacity over time and through repeated charge-discharge cycles.听

As the battery ages, usable capacity gradually declines due to a combination of increasing internal resistance and the gradual loss of active听Lithium and other electrochemical aging mechanisms.听

Engineers evaluate factors such as cycle life, capacity retention, and calendar aging to听determine听whether the battery can continue supporting the device throughout its intended lifespan.听For a deeper look at how cycling conditions affect long-term battery performance, download our whitepaper,听Lithium Ion Cycling Charge and Discharge.听

 

For primary听Lithium batteries used in implantable applications, which are not designed to be recharged, the focus shifts from cycle life to long-term energy retention.听

Since these batteries are not recharged, longevity is听largely determined听by self-discharge characteristics and the ability to听maintain听predictable performance over many years. Low self-discharge rates are critical to ensuring the battery听retains听sufficient energy to power the device throughout its service life.听

While the mechanisms are different, the听objective听remains the same: predictable, reliable performance for as long as the implant is expected to听operate.听

 

 

Testing for Long-Term Reliability听

Predicting battery performance over ten years requires more than standard testing.听

Because rechargeable and primary batteries age differently, they must be evaluated using different long-term performance metrics.听

For rechargeable Lithium-Ion batteries, engineers often evaluate:

  • Capacity retention over time听听
  • Cycle life under expected operating conditions听听
  • Calendar aging effects听听
  • Loss of active lithium and other aging mechanisms听听
  • Changes in internal resistance, especially in the first 500 cycles听

For primary lithium batteries, key performance indicators typically include:听

  • Self-discharge听rate:听Self-discharge rate for primary Lithium cells depends on temperature,听time听and discharge protocol.听
    • One advantage of medical implantable applications听is听the temperature is constant at 37掳C which听removes one听variable.听听听
  • Accelerated aging performance听
    • A significant advantage of primary Lithium cells is that accelerated aging at 72掳C is equivalent to 11.3 x over 37掳C.听听听听
  • Long-term energy retention over extended service intervals听
  • Predictable end-of-service voltage characteristics听
  • Overall reliability under expected operating conditions听

These measurements provide a more complete understanding of how a battery will perform throughout the life of an implantable device, not just when it is new.听

 

The Right听Solution听for the Right Application听

No two implantable devices have identical power requirements.听

Some applications听benefit听from rechargeable Lithium-Ion technology, while others are better served by primary听Lithium batteries designed for long service life. Factors such as energy demand, device size, therapy requirements, recharge strategy, and target longevity all influence the听optimal听solution.听

For many developers, an existing battery platform may provide the fastest path to development. Commercially available, off-the-shelf cells can help accelerate prototyping, reduce engineering complexity, and avoid the extended lead times often associated with fully custom development programs.听As discussed in this article,听“Implantable Medical Device Batteries 101: How to Choose the Right Power Solution“, off-the-shelf battery platforms can be a valuable option for early-stage development and concept validation while longer-term battery requirements are being refined.听In other cases, device requirements demand a custom solution听optimized听for size, capacity, form听factor, or performance characteristics.听

听

The ability to choose between proven standard battery platforms and custom-designed solutions gives device manufacturers greater flexibility as they move from concept through commercialization.听

Selecting the right battery is听ultimately about听balancing performance, safety, reliability, and product lifecycle requirements while ensuring the device can deliver therapy consistently throughout its intended lifespan.听

Ultimately, the听right battery is not necessarily the one with the highest听initial听capacity.听It’s听the one that can consistently and safely meet device requirements throughout its expected service life. Simply put, a battery’s true value is measured by听its performance听over time, not how impressive it looks on a specification sheet.听

 

Ready to Evaluate Your Implantable Battery Strategy?听

At听91快活林 Medical Power, we help device manufacturers develop power solutions designed for long-term reliability and predictable performance.听Whether听you’re听looking for a proven off-the-shelf battery to听support immediate development work听or a custom battery designed around your application’s unique requirements, our team can help听identify听the right solution.听

From chemistry selection and performance optimization to safety operations, scalability, and manufacturing support, we partner with customers throughout the product development journey.听

Ready to evaluate the right battery strategy for your implantable听medical听device? Contact the听91快活林听Medical Power team to discuss your application and explore off-the-shelf and custom battery solutions.听

 

Speak with a Medical听Device听Battery Expert Now!听