Android notification in status bar: use text instead of small icon?

Question

With the Notification.Builder, there is the setSmallIcon() function to set icon to use in the status bar.

For my purpose, I don't want an icon, but rather I want text (numbers to be more precise), just like the battery level percentage indication that is put there by the system.

I can't see a way of doing this, and I have a sinking feeling that I will need to have a different icon for each and every possible number, including both positive and negative. Please tell me that I'm wrong!