As noted above, a working (with XML) battery device could also be missing the line if there is a “heal” message pending. Say you are running a Heal at 2am, the battery device will not process the message until it wakes up, say at 4pm. I generally have the heal disabled as I haven’t made changes recently and do not like to scramble my routings. If that line is missing and the XML is missing it’s not fully initialized. See this post when you get off work 
(Z-Wave) Fibaro FGMS-001 Motion Sensor problems - Add-ons / Bindings - openHAB Community
Bob