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Discussing battery issues with biomedical technicians

August 09, 2019
HTM

5. Do you follow the date stamp or use common sense when replacing a battery?
Here the philosophy differed. One gentleman said he replaces the battery according to the mandated date stamp but most others use common sense, provided the evidence can be proven. Medical device manufacturers are aware of the shortcomings of date stamping and some have relaxed the policy.

6. How do you check battery capacity?
Many batteries and portable devices include a fuel gauge showing battery state-of-charge (SoC). While this is helpful, the readout does not guarantee runtime. A serious error occurs if an aged battery shows 100% SoC while the capacity has dropped to 50%. In this case, the runtime is cut in half. We ask, “100% of what?”

Unless checked with a battery analyzer, the true capacity remains unknown. Capacity is the leading health indicator that also determines end-of-life. When I ask battery users: “At what capacity do you replace the battery?” most reply in confusion: “I beg your pardon?”

7. What are the benefits of the smart battery?
Modern devices are equipped with smart batteries offering state-of-function (SoF) that is instantly readable. FCC (Full Charge Capacity) in a smart battery represents the “digital capacity” that correlates to the “chemical capacity.” The battery also has a digital serial number to track history with a database.

But the smart battery has room for improvement. Few medical devices present SoF in an easy to read format. SoF may only be accessible by an access code because manufacturers serving the consumer market are hesitant in offering too much information in fear of increased warranty claims. Biomeds also say that the “digital battery” causes more problems than the “chemical battery.” For safety reasons, many chargers are hybrid and switch to regular charging when the digital communications fails.

8. Would the Fishbowl work?
As presenter at the workshop, I proposed the Fishbowl (Figure 2) to provide battery SoF graphically. The icon shows SoC by the Charge Ring that moves counter-clockwise towards the Charge Alarm on discharge. The Status Dome spells out the battery status; Battery Fade is shown by a dropping ceiling in the Dome. End-of-life occurs when Battery Fade reaches the Pass/Fail line. Pressing the Dome on a touchscreen shows the Detailed Battery Information (Table 4). Figure 3 illustrates typical battery conditions portrayed at a glance.

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