What are these grey bar?

[Hearteater]

Ok, I don't power down ships that much, but when I do I see grey bars that don't seem to represent health.  See the attached examples.  All those ships are at full health, but the grey bars are at varying values.

[x4000]

I believe that's the shot recharge bar.  That bar shows normally, but goes down pretty fast so you might not notice.  But when you power them down, you're probably catching them in the middle of that.