I recently updated my nexus to 4.2 and usually when the battery goes dead I stick it on charge and the battery charge up screen comes up with the black background. Now I put it on charge and it actually turns on straight away to the lock screen but then turns back off due to low battery. This continues to happen even though I've had it on charge for 2 hours. Does anyone think its the update? It never used to come on straight away to the lock screen before.