Battery Maintenance and Diagnostics

MD&M West 2012 Event Coverage

Isidor Buchmann, CEO and founder of Cadex Electronics Inc. (Richmond, BC, Canada), will present “Battery Maintenance and Diagnostics” at the MD&M conference program on Wednesday, February 15. Cadex offers expertise in battery chargers and analyzers.

MPMN: What are some of the biggest battery-related issues currently affecting medical devices?

Buchmann: FDA has very stringent rules to get a product to market. But once a product is on the market, the battery is basically uncontrollable; nobody checks the battery and it will fade. Medical devices have to be calibrated and checked every so often. When it comes to the battery, however, the inspector just looks at the physical size, the weight, and the model number. If nothing is noticeable on the outside, the battery passes. But the battery could be virtually dead, and that’s not being measured because it’s difficult to do. That’s something fairly difficult for FDA to control. Information such as when users should replace a battery, how to measure capacity, and what are the signs or thresholds for when a battery should be replaced is not so clear.

MPMN: What should proper medical battery maintenance, diagnostics, and testing entail?

Buchmann: Batteries do not die overnight; they fade over time. Capacity is the leading battery health indicator and a battery is rated in capacity in terms of ampere-hours. So, a battery that is rated at five ampere-hours means that it can deliver five amperes per hour or one ampere for about five hours. The battery only delivers that capacity when it is new, however. It starts to age the first day it is “born” and immediately starts to fade whether it’s used or not. That’s where the problem lies—measuring capacity. Medical batteries are usually replaced when the capacity drops to about 75 or 80%. But there are no clean, quick measurements. That’s probably why the battery is not held to the same control standards as other aspects of a medical device.

As some form of control, we recommend a program in which a fully charged battery would be discharged on a battery analyzer while the capacity is measured. A method that’s very common in the public safety sector is labeling the battery; the label would include the service date, due date, and the measured capacity. The system is self-governing in that the user only picks a battery with a valid service date. Batteries approaching the due date are separated and serviced on a battery analyzer. If above 80%, they are relabled and returned to service. We suggest that the medical sector adopt this practice. It’s clean and simple.

MPMN: What demands has the medtech trend toward miniaturization and portability placed on batteries?

Buchmann: Wireless patient monitors are considered the fastest-growing sector. They’re almost like a cell phone in that the patient has to make sure that the battery is being charged regularly. But, again, the battery lives for only so many years and so many cycles. What happens if the battery dies or fails? Batteries account for about 50% of medical device failures. There should be battery maintenance and an indication of when the battery should be replaced so that the patient’s health is not being jeopardized.

MPMN: Does responsibility lie with the manufacturer?

Buchmann: Well, we’re not quite where we should be with battery fuel-gauge technology. Besides indicating state of change, medical devices should estimate the state of health of the battery and suggest replacement when weak. That doesn’t really exist effectively yet.

MPMN: What do you hope attendees learn?

Buchmann: I hope they gain a new understanding of the importance of the battery. No matter how much inspectors and FDA insist on checking everything else, if the power source dies, then the equipment goes with it. The battery should gain more importance when it comes to overall system management.

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