After updated my 520 to 8.1,it seems like the charging time reduced dramatically.when I was using windows 8 it took 3hr for full charge but after updated to 8.1 it's been something around 1.45 - 2 hr
That is interesting. Of all the advantages I have heard (faster internet responses, quicker app loading times), this is the first I have heard of charging times improving.
From my experience when a battery charges fully in a shorter period of time than that it used to in the past, on the same charger that means one thing. It's dying, the capacity the battery can hold gets smaller, so it takes less time to reach that lower amount of charge potential
Definitely not faster charging.. it is faulty WP8.1 battery status that reports 100% too early. Just try this
* make sure your screen is locked and visible
* turn off the charger [keep the wires attached]
* if the phone lights up too fast, its not charged fully.
* if the phone lights up late [3-5 seconds] it is fully charged