How to completely discharge iPhone if it randomly turns off?

Hello Andy,

Sadly, you cannot just connect your battery to a bulb to fully discharge it then charge it again and hope it works again. Firstly, because iPhones uses different connections to connect to the phones motherboard compared to normal batteries like AA or AAA, you cannot connect the battery to a lightbulb. Secondly, because batteries run on indedendent cycles of collection of electrons and releasing them to charge the phone (extra sciencey stuff), the battery cannot "recognize" a full charge. Your phone does that in its software. Throughout the phones lifetime, when you charge it, the battery loses some of its ability to hold a full charge and proceeds to get weaker and weaker. But either way, the battery will just need replacing. Because you are on an iPhone 4, the battery is really old and thay is why you are most likely having issues. Since the phone is so old, it may only he holding less than or equal to an 80% charge of its original capacity. So, unless you can get a new battery, you may need to upgrade your phone, or live with the issue.

Hope this helps!