Earlier today I was cleaning the area around where I keep the battery maintainer.
It is kept on a counter top about three feet from the bike, always plugged in except
for riding.

I noticed a couple of ants on it and watched as a good number of them were going in
and out. I picked up the maintaner and there were hundreds of them under it.

Between the ant spray and the compressor, I think I got most of them out, I also painted a coating of vaseline around the perimeter of the maintainer so they won't be able to get to it again.

I don't know if it's the hum, or the heat, but it's something to keep an eye on.