A while ago I made a post about the importance of battery replacement in polysix synths.
I just found a great example of how not to do this in a Korg DW-8000:
Instead of a CR2032 with attached solder tail, somene soldered leads to the battery directly causing it to heat up way to much. This damaged the battery and caused some leaking eventually. The battery acid destroys sourounding traces, vias and even ICs – very bad…
Much better to do it like this: