The MSI Wind U100 is officially available with either a 3-cell or a 6-cell battery pack. Our review unit is equipped with the 5400mAh 6-cell. MSI has designed the 6-cell in such a way so that instead of protruding from the rear of the notebook, it angles downward, lifting the chassis slightly. This is a bit more visually appealing and it may also have some minor benefits for cooling. However we did notice that since the chassis is so light, a significant portion of the weight of the unit can be attributed to the battery. Due to the battery's position, the Wind is somewhat back-heavy and rather easy to tip. While a light bump or nudge won't cause it to tip over, the Wind falls backwards onto its battery, lifting up the front-end, more readily than we'd like. Thankfully the shape of the battery pack prevents it from tipping all the way over making this nothing more than a minor annoyance. No need to worry about your netbook performing an impromptu backflip off a table.
In order to test battery performance, we used the Battery Eater Pro utility. We tested the Wind using Battery Eater's Classic and Idle tests. First we tested how well the Wind performed under ideal conditions using the Battery Eater idle test which simply idles the system until the battery drains. We also ran the test with the wireless radios turned off and the screen set to half brightness. Then we tested the Wind under stressed conditions using the Battery Eater Classic test. In this test mode, both the CPU and GPU are stressed to full load until the battery runs out of juice. The screen was set to full brightness for this test and the system was connected to a wireless AP and the Bluetooth was enabled.
Overall the Wind and its 6-cell battery performed very well. In the ideal settings test, the Wind kept going for just over 6 hours. That is roughly enough juice for an average day, considering the system would be allowed to enter power saving modes during normal use. The Wind's performance in our stress test was also fairly good. It managed just under 4 hours of juice while both the processing and graphics subsystems were fully maxed out. This should be a good indicator of how the Wind will perform in a worst-case scenario. Real-world performance will likely fall somewhere in between our two tests for continuous use or do much better than our idle test if your only using the Wind periodically throughout the day, allowing it to enter standby mode to save power in between uses.