Are you having any trouble with them "talking" to each other? If they do not see the transmitted signal they will continue to search for a signal, and will use more battery power doing that. Just an idea as to why they are killing the bats. Of course, it could just be a bad unit. Good luck on getting it straightened out, as you will love them when they work right. I would feel lost without mine.
UDS, cheap o grill, rusted chimney, yeller wannabe thermo pen, Maverick ET 732, 1950 model wife.