Discussion recently came up on how to appropriately log battery changes for an ELT. Since I have a repairman certificate, I should be able to do this however the individual with whom I was discussing this felt that I wasn't even able to do that much. Of course, that's wrong. I have an Avionics logbook with a line that indicates the date the batteries were changed and the date that the next batteries are to be changed. Is there another more extensive entry and I need to make and if so could any of you let me know the appropriate verbiage?