Lithium-battery formulation suits medical applications
By Margery Conner, Technical Editor -- EDN, July 21, 2009
EaglePicher Medical Power, a supplier of batteries to manufacturers of implantable medical devices, has recently introduced a lithium-CFX (carbon-monofluoride) battery chemistry. The technology, an enhancement of the company’s proprietary CFX-battery technology, results in a self-discharge rate of less than 1% per year at room temperature. Although lithium thionyl has a similar self-discharge rate, it increases rapidly with higher temperatures, making its use a liability in medical devices, especially implantable devices, such as pacemakers, which must operate at 98.6°F.
The CFX formulation also offers energy density of 180 Wh/l. Gregg Bruce, PhD, chief scientist at the company, estimates that this density is approximately 25% more than the density of battery technologies that medical devices currently use. By using a CFX battery, battery-pack designers can choose between a larger battery that runs for 25% longer and a 25% smaller one with an equivalent runtime, an important feature for implantable medical devices.
The CFX formulation incorporates an end-of-life indicator to accurately predict battery depletion six months in advance, requiring fewer replacement surgeries for implantable medical devices. The indicator manifests itself as a sharp falloff in voltage yet still maintains adequate voltage and power to operate. The new technology will be available in a number of configurations at powers of less than 350 mAhr to 10 Ahr.
