While opening up a battery pack (planning to ultimately replace the individual cells, I noticed what seems to be conformal coating. I was also suspecting flux, but in trying to clean it with 99% alcohol, the residue does not come off at all. This is overall leaving me to suspect some kind of conformal coating. The only issue is the application seems random as some components have it and others do not. This randomness of the coating applies to both passives, and ICs. Added a 2 additional images to imgur since total attachment sizes are limited and even compressing to 8MB leads to noticeable detail loss.
https://imgur.com/a/Qo9RSR2 The battery is a Dell 7WMM7 (I have 1 extra one that I swapped in), and since it is a rather old product, 3rd party replacements are pretty overpriced (in the $50 range).
The battery back suffered a weird failure where something leaked from the top right cell and corroded its connector, that failed cell also caused the pack to refuse to charge.
My plan is to simply remove the old cells, and find new pouch cells of the same size, and spot weld the tabs onto the tab leading to the resettable fuse for each cell.
Anyway, I was just wondering why some components seem to have a bunch of conformal coating while others have none.