Battery percentage would greatly reduce, like 73% then 20 min later be at 30%. You would plug it up and then it would show 69%.
Went well. Had trouble with the adhesive tab breaking off. Had to use spudger to pry battery up a little then I was able to use the tweezers to get the adhesive strip and was successful pulling it the rest of the way out.
The ifixit video that I watched didn't say anything about removing the screen but it clearly showed that it had been removed. Removing the screen made it a lot easier, especially if you run into an issue as I did. There are 5 screws holding a cover over the 4 screen connectors. Remove the cover then use the spudger to "pry" up the connectors, gently obviously. They are different sizes so the will only go on one way and the connectors are a specific length so it's easy to reconnect them. The video also didn't show the recommended way to install the adhesive strips. Line up the edge where the black tab and the adhesive meet to the end corner of the bottom of the battery. That leaves enough room for the tab to fold up around the end of the battery and stick to the top end of the battery and fold back so that it can be removed later if the battery needs to be replaced again. Also, I would pre-fit the battery by connecting it and adjusting the connector wire so that when you have the adhesive installed and are trying to get the battery lined up, you don't get the adhesive contacted with the phone case in the wrong position and have to try to reposition the battery and damage the adhesive strip or something else. I also had to bend some of the battery connecting wire down a little bit. The connecting wire was a little wider than the original battery wire so I held the connector down and used the spudger to bend down the part that was sticking up past the battery top edge.