How long should things last? I think it depends on what you are willing to tolerate. My daughters had this little Sesame Street® cassette tape player with a series of large colored buttons. The instructions were never to push the red button, which occasionally our kids would. This little player was used nearly every day for more than 6 years. Eventually things began to wear out. The first thing to go was the cassette loading door. After a couple of years, it would not always stay closed. My middle daughter asked if it was broke. I told her it was just wearing out. She asked me what the difference was. I told her that we could still use it; but that we would just have to set “Big Bird” on the door.
I had a similar experience with my first notebook computer. I wanted to keep it and use it until the purchase price, divided by the number of days I had owned it, was about a dollar. That ended up being about 2,000 days. Toward the end of its days, it was the plastics and mechanical parts that were giving me issues. For example, the hinges for the display began to stick, then break. I repaired them to the level I could tolerate the functionality. The charger jack became very loose and I repaired it to the point it was almost reliable. Yes, I had to bring it up to tolerable functionality. I since have changed my goal to somewhere between $3 and $5 per day of ownership for replacing my notebook computers. Luckily the price of notebooks has come down appreciably.
This brings me to our topic. While I used a dollar-per-day of ownership to target the replacement of my laptop, there are other targets. You may want to keep the equipment until the embedded battery no longer can support the run time expectations. I do appreciate the embedded battery strategy as long as the battery life meets my level of tolerance for truly portable operation. As a side note, I have an electric razor that has had the same battery for 8 years. I have gone through 5 sets of blades, but the battery still meets my expectations of 4 shaves per week before recharging is required.
Battery degradation is a popular topic or complaint. Most portable users just accept the phenomena. They live with it by purchasing a replacement battery, if their battery is replaceable, or replace the entire device. A colleague of mine, Yevgen Barsukov, presented on this topic of battery degradation at this year’s International Battery Seminar and Exhibit.1 Just knowing the kinetics of battery degradation can help determine actions that can reduce the rate of the phenomena. For example, temperature accelerates degradation and higher state charge further increases the reaction rate. So charging your device to full and then leaving it in your car in the summer, can take weeks off your battery’s life.
Battery degradation occurs in two areas: Coulomb losses and impedance increase. Read remainder on helping batteries last longer on EDN.com.
Let me know your experience with your embedded battery systems, particularly the ones where the battery is not replaceable by you.
Power to the people! ~Dave Freeman
Related Resources:
- System-side impedance-track fuel (gas) gauge direct batter connection evaluation module
- New Battery fuel gauge and charger chipsets with MaxLife technology allow consumers to charger faster without degrading the battery
- Fundamentals of battery fuel gauging
- Battery management solution
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