There is this paragraph:

Bigme promises that the 3,300-mAh battery will “maintain a charge for a remarkably long time” – though doesn’t actually specify how long that might be. You’ll need to plug in more often if you make use of the 36-level front light when strong ambient light isn’t available.

Vague, but that’s not the author’s fault. Aside from GPS, games are the other thing that uses loads of battery and you won’t be playing many graphically demanding games on that display - but we want numbers!