Chosen Solution
I replaced the battery and screen on an iPhone 6S for a friend. She ordered the parts off of eBay. She said that even though the screen was cracked, the LCD still worked. I first disconnected the battery and swapped it out. When I went to turn it back on, it made the noise like it recognized the charger, but the screen was totally black. When I swapped to the new screen, it had the same problem. The battery says that it has the same voltage as the OEM battery, but it was supposed to be 2200 mAh, as opposed to the standard 1715. I checked the connectors and they don’t appear to be damaged. Also, it is still able to receive texts. Every once in a while the phone screen will flash when it is turned on. I have changed a lot of screens in the past and have never seen this issue. Does anyone know what it may be?
When you replaced the battery, did you remove the screen to do so? And was the battery disconnected before and during the removal and installation of the screen? Leaving a battery connected while you fiddle around with the screen connectors can lead to blown backlight filters, which is exactly what your symptoms sound like. To be certain, shine a bright light on the screen immediately after connecting the phone to a charger or iTunes enabled computer. If you can see a dim image, then the backlight filter is blown.
This might just be either a short in VCC_MAIN or a bad battery. Try an Apple OEM battery and if that doesn’t work, then it probably has board level damage.
