This from a Which? report for an asspire 5336
Sadly, battery life is poor. In our tests, the 4400mAh cells only managed two and a half hours of video playback from the hard drive or web browsing before they needed recharging.
...and for a 5553
It's not such a great laptop for use on the move, for the simple reason that battery life is awful. Expect just two and a half hours of video playback and only just over two hours of web browsing using wi-fi.