On Dec 30, 2004, at 11:14 PM, Dan Crutcher asked: > Does anyone know of a way to make these spare Powerbook batteries > "keep" longer if unused. Or is it simply a necessity to use them every > so often to keep them from dying for good -- a "use it or lose it" > scenario?
A year or so ago, I was talking with a chemical engineering professor who does research on batteries and asked him how he thought portable batteries should be treated. He told me that Lithium batteries have a finite lifetime that starts counting down as soon as they come off the assembly line. The lifetime can be lengthened in a few ways. Use them regularly. If you put them in a drawer and let them discharge, irreversible chemical changes happen and the battery will have less capacity. On the flip side, they also don't find staying at full charge for a long time agreeable. So, don't plug them into a charger for weeks at a time. If they must be stored, discharge them to about half full and put them in a cool place. A refrigerator is probably good because it slows down chemical reactions, but below freezing is not good because there's stuff in the battery that can freeze. I asked about the idea of discharging completely every so often. He said that he didn't really know why that would help the battery, but there's power management circuitry on the battery that needs to be reset every so often as the capabilities of the battery change, and a very deep discharge would probably help with that. | The next meeting of the Louisville Computer Society will | be January 25. The LCS Web page is <http://www.kymac.org>. | List posting address: <mailto:macgroup at erdos.math.louisville.edu> | List Web page: <http://erdos.math.louisville.edu/macgroup>
