y iOS 8/iOS 8.2/iOS 8.3 Drains d Battery Too Fast?

1) Find the Power Hungry Apps.

Go to Settings > Usage > Battery Usage, and you will see a list of apps consuming battery on your devices in the last 24 hours and last 7 days.
2) Turn off Cellular Data

Internet on your phone is a must, but it's also a big power drain. For those of you using 3G and 4G data services, it is worth noting that they drain large amounts of battery on your phone. So when you are not using your data, it's best to turn it off by going to Settings > Mobile and pressing the Mobile Data switch.
3) Soft Reset After Update

So you've just got the brand spanking new version of iOS on your phone. Simply restarting it can help sort out quite a few issues with the software on an iPhone, but it can also help with fix some battery life problems. To conduct a soft reset, you can press the power and home button at the same time until the iPhone turns off.
4) Background App Refresh

If you are looking at completely stopping background app refreshes for huge savings on battery life, then Go to Settings > General > Background App Refresh and toggle the on/off switch. You can also turn Background Refresh off for all apps or just manage each individual app's settings.
5) Turn Down Screen Brightness

The screen is one of the biggest areas of battery usage on any smart phone. The brighter the screen, the more power it uses. Turn down the brightness to a more reasonable level by flicking up from the bottom of the screen to access the quick function toggles.

You should also make sure auto-lock is set to one minute by going to Settings > General > Auto-Lock so when not in use the screen will automatically turn off after a minute.
6) Turn Off Bluetooth and Airdrop

If you're not using Bluetooth to stream music, or share content with other Apple users, then turn it off.