I have a Nexus 5 (1.5yo; I know, it's old but still worthy!) and the boy was heavily suffering from short battery discharges. I'm a phone heavy user so I figured out I had depleted the battery's life, and decided to buy a new one.
I used that great iFixIt guide to replace the battery and everything is fine, except that my phone keeps lasting 2 hours and something after a full charge, just like it did with the old battery.
Are there any special procedures I can take to ensure I can have a lasting battery life, or could this be related to the power port or other internals? I feel the back of the phone overheated just like it happened with the old battery as well.
UPDATE: it seems that battery I bought was faulty. After some weeks the phone dropped on the floor and the battery stopped working completely. The new one I got from the warranty gave the phone new life, as expected :)