We all know that computer manufacturers tend to give predictions on the battery life that are normally not attainable, but is the OLPC also guilty of that? CNet got the idea that they should test the battery life on the OLPC to see what it truly is.
What kind of battery life is the OLPC supposed to have? As we’ve previously noted the OLPC is supposed withstand 10 to 12 hours of "heavy use" on a full charge, but what do they define as heavy use? Before we get into that let’s take a look at what CNet’s initial test results were:
The best of the NiMH (nickel-metal hydride) batteries produced a little over 4 hours of operation. Of the two brands of lithium-ion batteries tested, one was about the same as the NiMH batteries; the other ran for a little over 5 hours.
That doesn’t sound too bad at first glance, but the interesting thing was that the computer wasn’t doing a darn thing during the tests…it was idling! So that can hardly be claimed to be heavy use. Jim Gettys, the Vice President of Software Engineering on the OLPC, contacted CNet to tell them how they can configure their OLPC for maximum battery life:
- Configure the DCON (display controller) chip to refresh the display whenever possible, so the primary display clock source can be shut down (saving about 0.52 W)
- Turn off the backlight (saving about 1 watt)
- Optimize the wireless firmware to reduce power consumption (savings unspecified)
Doing all of that is supposed to get the OLPC battery life near the reported 10 hours, but they consider that to be heavy usage? Well, Gettys did. He said that the target environment would be such that those criteria would more than likely be met. The CNet reviewer didn’t feel the same though:
I think that the usage model for a classroom environment should assume that the backlight is on and that students are typing, drawing and making their way through computer-aided learning programs. In such an environment, the figures from OLPC suggest to me that the XO will run for only 4 to 6 hours per charge.
Even in a more official July 2007 battery life test the OLPC capped out around 5 hours and 30 minutes of battery life, and that’s with dozens of computers being tested some of which had the backlight off. Heck, my Dell Inspiron can get about 6 hours of battery life if I turn the backlight all the way down and turn off the wireless. And it has a Intel Core 2 Duo processor which has gotta suck up a lot more power than anything in the OLPC. But then again my computer wasn’t a mere few hundred dollars.