Skip to main content

Squeeze More Life Out Of Your Batteries


Power is, as the saying goes, "the new black". Both Intel and AMD are racing to lower the amount of power that your CPU uses; screen manufacturers are looking at more efficient backlights using LEDs rather than LCDs; and fuel cells and more efficient battery chemistries are attracting venture capitalist funding (even if they're not actually for sale yet). There's even an industry-wide extended battery life working group.

Despite all of this, we're still a long way from being able to do a full day's work on the average laptop. iPod batteries are also notoriously short-lived, and digital cameras eat AAs as if they grew on trees. And of course, the more extras your mobile phone has, the more likely it is to fade away just before an important call.

Until the next generation of technology comes along, you need to be smart about managing power. Here's our guide on how to get more run time with your laptop, MP3 player, smartphone or digital camera - without dragging a power cable everywhere you go.

Be Patient For More Power

When you get a new device, whether it's a phone, laptop, MP3 player or mobile phone, don't start using it as soon as it has the bare minimum of power. Plug it in and give it a full charge - up to eight hours for a large battery. This will ensure that the internal microprocessor that stops the battery from overcharging has an accurate measurement of the full capacity of the battery.

Lithium ion batteries don't have the memory effects you might have experienced with NiMH or NiCd batteries, so there's no need to fully discharge your battery time before each time you charge it. If you find that the estimated battery life is consistently inaccurate, then you can calibrate the battery by charging it fully and then discharging it completely. Some notebooks come with a utility to recalibrate the battery for you, and Apple suggests a slightly more complex procedure for various Macintosh portables at Note that this doesn't affect the actual capacity of the battery, just the battery life that's reported.

It's better not to run your Li ion battery down fully if you might leave it without charging for some time; the battery could get to a very low power state and you might not be able to recharge it again. It's also better not to leave your laptop plugged in all the time; this is not because keeping the battery charged fully reduces the capacity, but rather because the battery can overheat, which makes it less efficient at charging and will reduce overall life.

The total capacity of a lithium ion battery decreases over time, by about 1% per month on average; the number of times you can charge the battery is also limited, to usually between 300 and 500 charges. If you take care of your battery, you can expect to have around 80% of the original capacity after 300 charge cycles.

Batteries are designed to work best at normal room temperature, though you can use a battery at a wider range of temperatures than you'd be comfortable at: from about 50°F to 95°F (10°C to 35°C). You can store a battery at even lower and higher temperatures - from about -13°F to 113° F (-25°C to 45°C) - but the higher the temperature, the more capacity the battery will lose over time. If you know you won't be using a battery for a few months, charge it to about 40% or 50% before you put it away to minimize the loss.

The temperature of the battery also affects its performance; if it's too hot or too cold, it will have a lower capacity. If a battery is stored at too high a temperature for a long time it loses capacity permanently, so don't leave a battery in the sun or in the trunk of a car on a hot day.