Hunter Douglas shade battery level (Gen 3) - What am I doing wrong?

I've recently installed the Hunter Douglas interface created by@bujvary.

I would like to be able to access the battery level of each shade in a generic battery monitoring app. I briefly experimented with trying to get this data in rule machine, but even though the devices have capability "Battery", the returned battery attribute is always null. I assume I am either looking in the wrong place or doing something wrong. Any help would be appreciated.

I've got Gen 3 shades if it matters.