The fact is the charging devices much like putting water in a water balloon that is you can still up most of it pretty quickly but that last little bit if you're not careful you explode. So there's circuitry to make sure you don't overcharge the phone and that causes it to slow down so things take longer than you'd like.
With a powerful enough charger things go pretty quick and that's actually one of the tip as soon as Doug asked this question I found an article online to describe a number of different ways to speed up charging it will put a link to that our website.
In short some things you can do are:
1. Turn the phone off because then it's not trying to use the radios and the screen to access the Internet while it's charging
2. Another important point is to make sure and use the charger that provides the correct amount of voltage and amperage If you just plug your phone into a computer's USB port it probably doesn't have as much power as a little PowerBrick that came with your phone.
4. If you try to charge an iPad using an iPhone charger it'll charge but just really really slowly so make sure you use the right charger
I'll stop here but to look at the article on our website that explains a few more things you can do to speed up the charging of your device.