That shouldn’t be a problem. I’ll add it to my TO-DO list for the next version.

In the Settings file, you can configure when BatteryBar turns yellow (Low Battery) and when it turns red (Critical).

If I implemented this feature, it would occur when the battery reaches either
critical level (default is 20% I believe, but it is configurable) when the bar turns red

the ‘soft minimum’ level, which defaults to 5%, since most laptops essentially stop operating at about that level.

or a new configuration ‘notification’ level

I’ll think about the best way to do that.

Secondly, should a visual notification be provided as well? For example, a small popup would warn you that the battery is just about to die.