IPhone – Wi-Fi Disconnects When Locking iPhone

When the iPhone locks (the screen turns off) it goes into power savings mode. Sometimes, because it does not always happen to mine, it re-connects to the wifi.

Now if this is an Internet cafe, yes you will need to login again, because the router will assign a new IP address to them - which brings me to my next point.

If an iPhone disconnects from the network the router releases that IP address and other devices can take its place. When the iPhone then reconnects it needs a new address. Some iPhones do this and others don't - it may depend on how many devices are connecting at any given time to your set up.

Short answer: nothing you can do about it - it's just the name of the game with wifi networks.

If however you have a regular device (say at home) you can assign it a dedicated IP address, but in an Internet cafe this is not relevant.

Hope this helps answering your question.

After hours of testing many components, I think it's the battery at fault. Every battery has a processor inside of it which lets the iPhone know how much it's charged and handles other system-level battery stuff. The water must have majorly screwed up that processor and the battery itself, because I'll turn the iPhone on once and it'll read around 40% and it will work for 15 minutes straight, before I turn it off and then back on again. But then it'll either say something really low, like 12%, or really high, almost always in the 80%, but it will crash with the Blue Screen Of Death and restart itself. I put the battery from a family member's iPhone 5s in and it works, and no matter how many times I restart it, I get the actual charged percentage and no BSOD. I got this battery from iFixit, who I've had good luck with in the past.