Chosen Solution
A week ago my IPhone 6 didnt turn on, I opened it and the battery was 0V, so I changed it for a new battery, when I try the new battery the first time my IPhone 6 turned on.However, then I turn off in order to put the screws and then it didnt turn on again, and the new battery is 0V too now.
Where did you get the battery? The iPhone 6 Battery from iFixit is a tested and safe battery. Using off brand batteries or untested batteries is dangerous, and they could even explode or catch fire. Use safe batteries. If you did get a battery from iFixit, use a multimeter to test the wattage and voltage of the pins on the battery.
Probably it’s too late for you, but for others with the same problem, give the battery a direct recharge and it will come back to life . (i would say 4V for 1-2 min) Worked for me :D
