Another flagship phone announcement and another battery problem. After Samsung's burning battery issue with the now defunct Note 7 Model, a lot of effort has gone into trying to make the batteries safe. Unfortunately, by their very nature lithium batteries can be volatile.
As you can see, iPhone 8 is suffering the battle of the bulge.
After reports of this occurring in Taiwan, Japan, China, Canada, and Greece BTR.com is reporting cases in America. Seeing a lithium battery swelling up is not unusual, it's actually very common. We have replaced several hundred which look like this, what unusual is that it is happening in brand new phones. It's important for iPhone users to know that when the battery life starts to become poor, and especially if you see the battery percentage dropping suddenly, and raising suddenly on charge, that the battery is damaged and needs replacing. If it is not, the battery will swell up and lift the screen. Now you have gone from needing a new battery, to needing a new screen as well
Below is a swelled battery from an iphone 6, next to a new one, it's pretty clear the damage that this can do in a tightly packed place like a smartphone.
The other issue is that swollen and damaged batteries can catch on fire. If you suspect that this may be occurring in your phone, I suggest taking it to a professional repair store immediately to have it checked out. Please refrain from charging it or leaving it on in hot environments until then, as this exacerbates the issue.
However, if this happens to an iPhone 8 I would recommend taking it straight to Apple and asking for a new one, as there is no good reason why this should be happening so soon.