Jay Honeck wrote:
The shop that does my annual repaints the battery box every annual.

???

I can think of no valid reason for this.

My shop usually does (maybe they occasionally skip a year). The
reason is that the non-sealed battery usually has seeped some acidic
residue somewhere in the box. That stuff needs to be brushed off
properly, which usually scratches the paint, which requires that the
box be painted afterwards, to protect it from any new seepage.

John Galban=====N4BQ (PA28-180)