Battery Maintenance and Diagnostics in Healthcare

How can the state-of-health of a battery be measured and how does the hospital know when to replace the pack? The battery analyzer becomes the integral tool in performing this important task.
Over the past few years, battery analyzers have gained steady inroads into hospitals and emergency institutions. These organizations have realized the importance in knowing the status of each battery in service. Because of the finite service life of a rechargeable battery, hospitals need to know when to weed out the deadwood. Organizations that make use of battery analyzers commonly service the batteries every 2-3 months and replace those that fall below 80% capacity.

Cutting battery costs in hospitals

Dave Marlow, Biomedical Technician, from the University of Michigan Hospitals and Health Centers in Ann Arbor says that: “Due to cost cutting pressure, we have to do more with less. We have found that by keeping track of battery history, we can determine when a battery starts to fail in an application. We then set routine test and replacement recommendations.” The University of Michigan Hospitals has been using Cadex battery analyzers for many years.

There are three philosophies governing reliability and cost of batteries. To begin with, the equipment manufacturer sets very conservative time limits in terms of battery service life. They advise to use only well-known brands and recommend frequent replacements. The purchasing agent, on the other hand, tries to cut cost by stretching the battery life as long as possible. They say: “If the battery can be used longer, why throw it out while it still has life in it?” The third philosophy is purchasing a low-cost import, possibly from Asia. Although lower in expenditure, many users have learned that lesser-known packs exhibit significant variations in performance. So who is right?

Cost-conscious battery users are willing to experiment and a battery analyzer can satisfy all three curiosities. By stretching the allowable performance bandwidth by keeping the battery above 80% will satisfy both the safety-conscious equipment manufacturer and the frugal purchasing agent. Being able to test lower cost batteries, less-unknown brands can also be evaluated.

Dave Marlow comments further: “With the combination of routine testing and replacement based on actual data, our hospital can maximize reliability and still reduce cost. We also look at the individual battery history to predict failures.” In terms of end-of-life capacity threshold, Marlow comments: “For lead-acid batteries we have found that an 85% capacity cut-off is preferred over 80%. Near the end of their cycle life, lead acid starts to loose capacity rather quickly. If allowed to drop too deeply, the ailing battery often fails to provide sufficient warning of the pending failure.” Regarding lithium-ion batteries Marlow states further: “In some applications we may continue using smart lithium-ion batteries until the packs drop to 50% capacity. This is the sharp knee in their failure curve.”

Summary
Problems with weak batteries are most apparent during emergencies and heavy traffic when full performance is needed. Battery failure during such critical moments is simply not an option. To strengthen the battery fleet, organizations are beginning to take a proactive approach in terms of battery maintenance and record keeping. The cost savings are apparent. Longer battery life, fewer unexpected downtimes and less instruments needing repair are the direct result. Best of all, the batteries can be used longer without compromising reliability.