Pokemon GO, like Niantic's first game Ingress, uses quite a bit of battery. This is to be expected since you are using GPS the entire time, your phone's display is on - and since you're outside, you are likely at full brightness and using 4G LTE. Using all of these together means that your phone is going to drain pretty quickly. And once you're out of battery, you're likely done playing the game, at least for now. Luckily, there are some ways to optimize your battery life while playing Pokemon GO.
The first way to do this is to go into the settings and turn on the battery saver mode. This doesn't do a whole lot, but what it does is when you hold your phone upside down, the screen will go black. So while you're walking, you'll still get credit for going the distance to hatch those eggs, and it'll still vibrate when there are Pokemon nearby. But with the screen black, you'll save at least some battery.
Other ways to improve your battery life is to turn down the screen brightness. Now if you are outside, you'll still need to have turned up pretty far, since the sun can be pretty bright. Another way is to perhaps knock your phone off of LTE and put it on 3G or even 2G networks. Luckily, Pokemon GO doesn't use a ton of data, so that 4G LTE isn't absolutely necessary, but it is of course nice to have.
There\'s one more way to save some battery here, and it's something that may take away from the game experience itself. That is turning off the camera. When a Pokemon appears, it uses your camera to show the Pokemon in real life (that's what augmented reality or AR is). Obviously, since the camera is on and being used, it is using more battery power. So simply turning off the camera should help save at least a little bit more battery life while you're out catching them all.
While these tips may not double or triple your battery life when playing Pokemon GO, they should at least help you get a bit more out of each full charge. Of course, if you don't want to change your gaming experience in Pokemon GO, you can pick up a battery pack, and charge your smartphone on the go, even while you're playing. We have a whole list of great ones here.