One of my lossless music DAP (Fiio X1, 1st generation) has a lithium battery that swollen up so bad it has popped open the back panel.
While searching out online how to replace it and looking up a replacement battery, I found out it can run without an internal battery while plugged into a USB power source.
This is a huge relief. I can just have it plugged into USB with phone charger battery if I need it to go anywhere, and I don’t have to wait weeks for a battery that might work inside it after soldering it in.
As an additional bonus, I found out an updated firmware had been released years after I bought it, and now, after updating, the user interface is snappier and everything is working faster.