I have a USB APC UPS connected to pfsense and nut package installed and appears to be working.

Due to the fact that I have a couple of low power devices connected to the UPS as well that I'd like to run on for as long as possible…

How do I config the NUT on pfsense to shutdown pfsense when it's been on battery for 5 minutes.
If mains power returns with in the 5 mins, then of course stay on and don't power off.

Sorry if this has been covered before, but I couldn't easily find it.
Thanks
Chris