Battery life is very important on tablets and the ASUS Transformer uses a 7.4V Lithium Ion Polymer battery. This battery is rated as being 3300 mAh and 24 Wh and ASUS says that it should last for a healthy 9.5 hours of Wi-Fi browsing and video browsing or for 16 hours if you are using the optional dock that contains a second 24 Wh battery.
We wanted to test out the battery on the ASUS Transformer, but we did so using our own methods. When we travel we use our tablet PC to watch movies. Most of the time when we are on a plane or stuck in a car on a road trip it is during the day and you have to crank up the screen brightness in order to be able to see anything. We increased the screen brightness to 100% and left Wi-Fi enabled as with inflight internet and smartphone teethering being more adopted we felt that was the best way to test tablets for our readers. Some sites turn off Wi-Fi and lower the screen brightness, but we don’t feel that is something most people do in the real world.
We wanted to put a full length movie on our tablet, so we turned to Slysoft for a solution. We were able to use AnyDVD HD and CloneDVD mobile to ‘backup’ our store bought DVD movie on our laptop. For this review we used the movie ‘Something Borrowed‘.
We converted the movie from MPEG2 to MP4 at a video bitrate of ~2500 kbps. We then transferred the file to the tablets with the included USB data cables. We then played the movie with the built-in gallery player until the each tablet shut down when the battery died.
The ASUS Transformer lasted for 6.2 hours, which is enough time to watch ~3 movies depending on how long they are! The Motorola Xoom lasted 37 minutes or 10% longer than the ASUS Transformer, but the two are pretty close together when it comes to battery performance. The ASUS Transformer really shines when you plug it into the docking station as our battery life jumped up to 11.2 hours. This is nearly double what the Transformer tablet gets on its own and is a very impressive time considering the Wi-Fi was left enabled, the screen brightness was cranked up to 100% and we were playing back a fairly decent standard quality movie!
Once your tablet PC battery dies you want to get it fully recharged as soon as possible, so we timed how long it takes to get the tablet back to a fully charged status indicator. The Motorola Xoom was able to fully recharge in just over 2.5 hours using the wall charger that comes with the tablet when you buy it. The ASUS Transformer took just shy of three hours to recharge.
During our testing and use of the ASUS Transformer we did encounter a battery drain issue that the Transformer community already knows about when using the dock. The ‘MobileDock Battery Saving Mode’ doesn’t work properly with a hardware component inside early docks and it has to be replaced by ASUS. This battery drain means that the ASUS Transformer sucks down a town of battery juice when it shouldn’t when the dock is plugged in and the tablet is supposed to be asleep. ASUS confirmed that this issue has been resolved and that our used loaner test unit that we got was one of the originals that had the issue. We didn’t do any real standby testing for this review, so didn’t wait for ASUS to send us a replacement.