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In the olden days, we dealt with NiCd batteries and were glad to find anything that recharged better than a zinc-carbon battery. We had to put up with battery memory effect, which meant that we had to fully discharge the batteries before charging, and ensure that we fully recharged the batteries each time for the recommended amount of time.

Fortunately, we're starting to get past that, and we now have lithium-ion battery technology that frees us from battery worries. Or does it?

Everyone knows by now that even lithium-ion batteries have a limited life, but what's the best way to preserve them and ensure that your cell phone or laptop will run for a reasonable length of time on its lithium cells years from now?

To answer that question for myself, I read the article How to prolong lithium-based batteries. It's enlightening, and worth reading if you have the time and the inclination. There's a summary at the bottom of the article, but I decided to write my own summary, which served my purposes a bit better.

Here's what I came up with:

• Keep it cool. If you're running a laptop on A/C power, remove the battery. (But don't let dust accumulate or enter through the laptop's battery opening.)
• Try to keep your battery at a 40% charge level. That is, constantly charging it to 100% of its capacity shortens its life. I didn't infer that one should partially charge a battery; but it seems that waiting until its indicator is at lesss than 50% before charging might be a good idea.
• Also note that frequent, full discharges are harmful, so it's not a good idea to let it run completely down before charging. (But, if you have a digital battery charge indicator that you suspect isn't reading right, you might want to fully discharge and recharge the batteries. That sometimes lets the charge indicator recalibrate itself.)
• Buying a spare battery and storing it isn't a good idea because lithium-ion batteries need to be exercised. A better idea would be to plan to purchase a new lithium-ion battery when it becomes apparent that it's needed. (Typical batteries last two to three years. Reduced run-times are the primary symptom of the need for replacement.) Batteries should not be purchased from discounters since those tend to be older batteries to begin with.