Now that your phone is smart, shouldn’t your phone’s battery be smart, too? That’s the idea behind Battery Extender, an app that promises to stretch battery life on many S60 3.x phones. The app works by monitoring your phone’s battery; when it sees that the charge is low, Battery Extender disables power-hungry functions that you’ve pre-selected, thereby extending your battery’s life.

In fact, Battery Extender’s developer, Ravensoft Ltd. , says the app can extend your phone’s battery by as much as 30 per cent. That could mean needing to charge your phone battery only every four days instead of every three. Over the course of the year, that would save you more than 30 charges. Not only would that reduce your power usage (and inconvenience), but it should also extend the effective life of your phone’s battery. The following chart, provided by Ravensoft, shows typical battery-life extensions for Battery Extender’s various settings:

Of course, your mileage may vary: The degree of battery extension depends on your phone usage and, more important, your Battery Extender settings. In all, there are seven functions you can adjust: backlight brightness, backlight timeout, screensaver timeout, GPS, Bluetooth, Autorotate, and applications.

To adjust Battery Extender’s settings, open the app and you are presented with the configuration page. Here you decide which of the main settings you want, as shown below:

The basic idea is that as your battery begins to lose its charge (indicated by fewer bars displayed), you cut back on nonessential functions. Battery Extender lets you select which of your phone’s functions will be affected, as shown in the screenshot below:

In the screenshot below, you can see that I’ve set my screensaver timeout to get shorter and shorter as my battery, as indicated by the charge bars, loses power:

Once you complete and close these settings, Battery Extender continues to run in the background, monitoring your battery charge and, when the time is right, disabling the functions as you’ve selected them. These functions include: backlight brightness, backlight timeout, screensaver timeout, GPS, Bluetooth, Autorotate, and applications.

Cool options exist, too. For example, if you’re going away for the weekend, switch to the Max Battery profile, and all power-saving options are set to their highest level. The Outdoor profile is great for joggers and others who want to geotag photos; it switches off several functions, giving over more battery power to your phone’s GPS function.

Battery Extender has been tested by Ravensoft on the following Nokia S60 3.x devices: E50, E65, E66, E71, N95 8GB, and N95. In addition, Ravensoft says users have tested it with good results on the Nokia E61, E63, E75, N73, N78, N80, and N82. For my review, I used a Nokia N95 8GB.

There are two versions of Battery Extender currently available on Ovi Store. The Full version sells for $6.99 (soon to be lowered to $3) and gives you all the features on an unlimited basis. A free version gives you all the features, but only for a 14-day trial.

In addition, Ravensoft says it will soon introduce a Lite version; free on an unlimited basis, it will offer only 2 of the 7 features currently supported on the Full version. In other words, the free Lite version will still extend your battery life, just not as much as the Full version does. Either way, this app goes a long way toward making your battery at least a little smarter.