If you use your iPad’s power brick to charge your iPhone 6, its battery will fill up faster. This unadvertised yet supremely handy feature was first spotted by MacRumors and iLounge and can be confirmed through a Mac’s built-in System Information app.
Although the newest iPhones still come with the same familiar small white power brick rated for 1 ampere and 5 watts, the iPhone 6 and iPhone 6 Plus can take advantage of the 2.1A and 12W charger included with the iPad Air to charge more quickly. It doesn’t just work with Apple-branded chargers, either: Any 2.1A charger can provide an extra bit of current to the latest iPhones, including high-wattage USB ports on newer laptops.
A 2.1A charger should be able to fill up an iPhone 6 battery up to 90 percent in about two hours. As other smartphone makers like Motorola tout faster charging as a differentiating feature, it’s odd that Apple wouldn’t update its included power bricks or tell consumers that this feature exists.
You’ve always been able to use an iPad charger with the iPhone, but the iPhone’s hardware used to only draw as much current as it could handle (which is 1A for the iPhone 5S and before.) Some battery experts warn that more amperage — “quick charging” — could reduce battery lifespan, although that matters less if you replace your phone every few years.
Source : You can charge your iPhone 6 faster by using your iPad charger, Kif Leswing ( https://gigaom.com/2014/09/23/how-to-charge-iphone-quicker/ )