See if I can get battery runtime information out of UPS

The UPS I'm running is a Lowell Power white-label version of an Xtreme Power Conversion [P80 Pure Sine Wave Line Interactive UPS](https://www.xpcc.com/products/p80/).

When I grab the UPS info, the battery runtime always reports as `0`, even though the front display on the unit displays a runtime in minutes, and it's pretty accurate:

```
$ upsc server-room-rack
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battery.charge: 24
battery.energysave: no
battery.packs: 1
battery.protection: yes
battery.runtime: 0
battery.voltage: 50.60
battery.voltage.nominal: 48.0
device.model: LILVX2K0
device.type: ups
driver.name: nutdrv_qx
```

I'm wondering if it's a quirk of the `nutdrv_qx` driver, the UPS, or what...

Reproduce the report with `upsc server-room-rack` and inspect the `nutdrv_qx` handling for the linked P80 model. Determine whether the zero runtime comes from the UPS or the driver, then make the runtime information report correctly or document the limitation.

Written by the indexing model from the issue text.