The iPhone 4S’s battery-drain problem has been a hot issue over the past week. Apparently the location-services system in iOS 5 is the main culprit behind the rapid loss of battery power. Apple has acknowledged the situation and released a beta version of iOS 5.0.1, a future update that corrects the problem.

But the iPhone 4S is not the only smartphone with troublesome battery life. As my colleague Jared Newman puts it, “smartphone batteries stink.” For instance, when the HTC ThunderBolt and the Samsung Charge debuted earlier this year, customers reported a poor battery life span when each phone was hooked into Verizon’s 4G network.

We wanted to see how the iPhone 4S compared to other top smartphones. Since this is just a sample comparison, it isn't the final word in battery life testing. For this article, we used the AT&T version of the iPhone 4S; your experience may vary depending on your carrier.

We’ll revisit these tests once iOS 5.0.1 is released to the masses, and we'll compare the iPhone 4S against the soon-to-be-released Motorola Droid Razr and the Galaxy Nexus, both coming to Verizon. In our next round of tests, we will also include the most recent BlackBerry models, as well as Windows Phone handsets.

How We Test

Our lab analysts evaluate a phone’s battery life during typical use by playing a video file at maximum brightness with audio set at a volume level that's loud enough to be heard clearly in an office setting. We run the tests over PCWorld’s Wi-Fi network. The video file is a 720p high-definition animated trailer that we play in a continuous loop until the battery gives out, at which point we log the total battery life using a standard-grade stopwatch. Our lab analysts conduct two passes of the test and then calculate an average time in hours and minutes.

The Results

The Samsung Epic Touch 4G (Sprint’s Galaxy S II phone) had the longest battery life span at 7 hours, 22 minutes. The T-Mobile MyTouch 4G Slide came in second, running for 6 hours, 33 minutes. Surprisingly, the iPhone 4S came in a close third--despite all of the issues and controversy--with a time of 6 hours, 14 minutes. The remaining phones had similar, and significantly shorter, running times. It didn’t seem to matter what the manufacturer was, either, as the bottom results were a mix of HTC, LG, and Motorola phones.

The Battery Life Conundrum

Judging from our results, the iPhone 4S’s battery actually looks good, mainly because the others are so dismal. Fortunately, you have many ways to preserve your phone’s battery life: You can adjust the display brightness, turn off location services, purchase an extra battery, buy a battery case, go easy on the GPS, and the like.

But really, why should handset owners compromise their smartphone use? Smartphone technology is rapidly evolving, gaining everything from 3D displays to quad-core processors to faster networks. But what good is a quad-core processor on a mobile device if you can’t enjoy more than a few hours of gameplay before you have to plug the phone in? It kind of defeats the "mobile" part of a mobile phone.

Regrettably, battery life likely will continue to be an issue for smartphones over the next few years. As processors become more powerful, and as more phones switch to LTE technology, your phone's battery life will continue to suffer. Some good news is on the horizon, however. According to Ramon Llamas, a senior research analyst for IDC Mobile Devices Technology and Trends, portable charging products will improve, including cases with extra (and, we hope, longer-life) batteries.