The Sony Xperia Tablet S comes with a 6,000mAh lithium ion battery. 6,000mAh isn't really very much; the Google Nexus 10 has a considerably larger 9,000mAh battery, while the iPad 4 has an almost twice as big 11,666mAh battery.
Sony claims you'll get 12 hours out of it before it'll need a charge with 'standard usage'. Unfortunately our idea of standard usage seems different to Sony's. Sure, if you have the screen off and don't interact with it the tablet will last for days, but as soon as you start using it the battery begins to plummet.
As with most tablets, the screen seems to be the biggest drain, since listening to music with the screen off saw quite a slow drain (around 4% an hour). On the other hand, spending about 15 minutes shooting videos and taking photos drained the battery by 10%.
We ran our standard battery test on it (playing a ninety minute video when the device is fully charged, on full screen brightness, connected to Wi-Fi and sending push notifications from email accounts and social networks).
By the end of the video the battery had dropped to 62%, which is a huge drop, particularly considering that the screen doesn't get all that bright to begin with, so you may well even want it at full brightness.
The Sony Xperia Tablet S's battery life really did disappoint us. We weren't thrilled by the battery in the Google Nexus 10, but even that outperformed this, while the likes of the Google Nexus 7 and the iPad 4 both blow it out of the water.