No power, battery voltage dropping off.

I’m trying to repair a PS4 controller that isn’t powering on. I started by checking to make sure that the battery and USB port were working, and didn’t find a problem with them. When I started looking at individual components on the board I noticed that when I plug in the battery, it sits stable at 3.4V for a few seconds before dropping to around 1V. I tested the battery with a different board and found that the voltage stayed stable at 3.4. Does anybody have any suggestions for what might be causing this?