My Nexus 7 tablet shuts down all of a sudden though it may have shown 50% battery remaining a few minutes back. I use it only as an e-reader (Kindle) – it doesn’t last even a few minutes (after full charge) if I use internet (like YouTube or something). It’s quite old – got it in 2007! As a reader it lasts quite long, even while day. But then it shuts down suddenly.