Chosen Solution
replaced battery, will not power on?
Did you buy it from ifixit? Did you remember to disconnect the screen before disconnecting and reconnecting the battery? If not you probably burnt your LCD.
The first thing I would do is see if your original battery will allow you to power on the phone. If that works then you have a bad battery. Check to make sure all your connections are secure as a ribbon cable being off could cause the same results. Here’s what could be going on. You just got a bad battery. Your screen is not connected properly or you shorted it out. You shorted out your phone during the repair. If you did not use an anti-static wrist band then it’s possible you zapped your phone in the process. I have personally never run into this however it’s still a possibility.
