A little over three years ago, you, the readers, asked us, the Ars staff, about the best way to prolong the life of a lithium-ion battery. Now that time has passed, the gadget landscape has changed, and it's time for an update. There are a few new things to look out for, but mostly the principles we stated then, stand today: "Use your battery. Not too much. Mostly for small apps."

Our initial guide clarified a great many things about lithium ion batteries and the ways they can differ from other types of batteries. These differences once used to strike fear into the hearts of consumers. For instance, Li-ion batteries, unlike nickel-based batteries, and don't get their capacity "confused" by shallow discharges. In fact, frequent and shallow discharges are the best advice for keeping a young Li-ion battery fit and trim.

One of the worst things you can do to a Li-ion battery is to run it out completely all the time. Full discharges put a lot of strain on the battery, and it's much better practice to do shallow discharges to no lower than 20 percent. In a way, this is like people running for exercise—running a few miles a day is fine, but running a marathon every day is generally not sustainable. If your Li-ion-powered device is running out of juice on a daily basis, you're decreasing its overall useful lifespan, and should probably work some charging stations into your day or change your devices' settings so that it's not churning through its battery so quickly. There used to be certain types of batteries whose "memory" of their total charge capacity seemed to get confused by shallow discharges. This is not, and never was, the case with Li-ion batteries. However, if you are using something like a notebook computer that gives you time estimates of how much longer the battery will last, this clock can be confused by shallow charging intervals. Most manufacturers recommend that you do a full discharge of the battery about once a month to help your device calibrate the time gauge. …On the other end of the spectrum, keeping a Li-ion battery fully charged is not good for it either. This isn't because Li-ion batteries can get "overcharged" (something that people used to worry about in The Olden Days of portable computers), but a Li-ion battery that doesn't get used will suffer from capacity loss, meaning that it won't be able to hold as much charge and power your gadgets for as long. Extremely shallow discharges of only a couple percent are also not enough to keep a Li-ion battery in practice, so if you're going to pull the plug, let the battery run down for a little bit.

The other tip that remains true is that you should keep Li-ion batteries in fair weather. They don't like extreme cold or heat, especially heat caused by running Crysis 2 clock-speed drag races or whatever the kids are up to these days.

Another thing that Li-ion batteries hate is heat. This somewhat less of a problem for cell phones, but a big problem for notebooks. Even using a battery at room temperature for a year can bring its capacity down by as much as 20 percent, and the interior of most computers is a mite cozier than than that. So in a unfortunate twist of fate, laptop batteries usually spend the most time in the worst possible state: plugged in at 100 percent charge, running at an elevated temperature.

An interesting development since we wrote the first edition of this article is that Li-ion batteries are less likely to find themselves in very hot environments as a result of the device they're powering. Devices are better at heat regulation today and, thanks to flash storage, tend to have fewer moving parts. We should now have an easier time getting long lives out of Li-ion batteries without having to change our behavior much.

These days, temperatures can be slightly more of a problem for smartphones, where hardware still has to operate in very tight quarters. For this reason, it's best to keep them out of situations that are already hot (sunlight, pockets, under pillows).

But it's also helpful to try and keep tabs on whether your phone is needlessly spinning its processing wheels, which is harder with some platforms than others. With Android, this is a little easier to suss out using the usage stats and process-manager interfaces. If something is idling and cranking up the temperature on your phone, kill it.

iOS devices are a little harder to manage in this respect, but overthought.org recently ran a great guide to troubleshooting a wayward device or apps that are draining the battery needlessly.

As we noted in the first edition of this guide, another of the Li-ion battery draining sins are fast, intensive drains:

Running the battery out very quickly by drawing a lot of power at once is another way to cause it a lot of strain. For example, running a graphics-intensive game on a smartphone or a notebook for a couple of hours while unplugged is worse for the battery than depleting it over several hours while e-mailing or Internet-browsing (heat is a factor here, too). Again with the running analogy: it's probably harder on you to sprint a mile than to jog it.

Another piece of advice in the new age: as Gizmodo notes, while wireless charging is fun, using it may come at a cost to your device's battery longevity because it can produce excess heat, more so than a simple plug might. Given how much wireless charging solutions cost, I suspect if you're using one, you treat gadgets more like candy than children, so this may not be much of a concern.

Otherwise, the principle I first wrote stands: use your battery. Not too much. Mostly for small apps. Go forth and discharge. But gently. Ever so gently.