I have a Kwikset 914 lock that does not report battery level. Had the same issue on ST after changing the battery several months ago. Found a thread on ST about this, one person added a few lines of code to ask for battery level when doing a refresh and seems like it was successful. How do I get the code for the stock driver so I can try adding these lines?
I did a quick sloppy copy of ST's Z-Wave Lock DTH over to HE and added one line to the refresh function. Now have battery level on my lock. There's some other things that I'm sure are not right since I'm copying code from another platform but this appears to correct the issue with battery level missing.