I got to talking last week with Kiera Butler of Mother Jones magazine about the best ways to keep the rechargeable batteries in laptops and mobile phones healthy and long-lived.

Like all batteries, rechargeable batteries wear out over time. Dell says that a full life span for a garden-variety lithium-ion laptop battery is 18 to 24 months. A cell phone battery can last the same length of time, and is good for approximately 400 recharges. The average life span of a cell phone, however, is only 18 months, so a single battery should last the lifetime of a mobile phone.

In order to keep rechargeable batteries healthy, the refurbishers that I've spoken to about this tend to agree that with lithium-ion rechargeable batteries that power most laptops, mobile phones and tablet computers, it's not good to let the battery go below 10% of its charge.

If you want to be radical about battery maintenance you can "calibrate" it once a month or so. That's a technique in which you let the battery run down or discharge to below 20% and then fully recharge it without interruption. This technique works for computers but not for most cell phones, which don't provide a reading on the percentage of the charge on the battery.

Batteries also last longer in cool conditions. They like a temperature range of 32 degrees to 95 degrees Fahrenheit (0° to 35° Celcius). It's not good for the battery to leave a cell phone or portable computer in a hot car for long periods of time.

Also it doesn't harm lithium-ion batteries to keep your laptop plugged in to AC power most of the time when you're using it because modern chargers are designed to shut off when the battery is fully charged. However, it's best to unplug a laptop or phone if you're just storing it for some days. It's best if you can charge it up first before storing it.

Finally, you'll know when your battery is getting old when it stops holding a charge very well, only 30 minutes or so, or a quarter of it's original capacity. When it's time to recycle it, just go to Earth 911 to find the closest place to properly recycle it.

Lithium-ion batteries are actually pretty benign environmentally. The U.S. EPA classifies them as non-hazardous waste, but lithium is an alkalai metal that is flammable. It is mined mainly in Chile and there are also large deposits in Bolivia. The mining and processing of lithium carbonate is a polluting industry (although not on a par with coal) and demand for the metal is skyrocketing with the advent of electric cars and the increasing production of portable electronic devices, so reclamation of the lithium is the main reason to recycle lithium-ion rechargeable batteries.

The best thing I've seen so far on the big picture on lithium is the book Bottled Lightning: Superbatteries, Electric Cars, and the New Lithium Economy.

How well do you maintain your mobile batteries? Share your thoughts in the comments below.