If you have an iPhone battery swelling up and expanding, it's best to take the cell phone to your nearest Apple Store to get the battery replaced. The store may replace the battery for free since a bad battery can become a hazard (causing a phone to catch on fire or explode). Alternatively, an authorized Apple repair store could help fix the issue. For more on phone battery risk & safety information, check out Leo's recent episode of Ask the Tech Guy at https://youtu.be/LRfvgTFE9zk
Mike has a Motorola G4 and he wants to know if it's best for his battery to keep the phone plugged in whenever possible. There's been articles that claim it's best to do it differently, though. Leo says there's a lot of lore about lithium ion batteries, and Leo isn't even convinced that we understand how they really work. Leo gets his information from BatteryUniversity.com.
Owning a smartphone can often be a balancing act of usage and power conservation. If you're noticing that your phone is draining a lot quicker than usual, however, there is a way you can easily find the culprit. iOS and Android both offer statistics on what apps are using up your battery.