One app (Skype) using all my battery

One app, Skype, is using like 30% of my battery power. The issue is that I'm not even using Skype, except a few times per year; for those occasions I would like to have it installed. But I don't want it to use 30% of my battery every day! I have disabled background activity and notifications for skype, but it still uses 30% of my battery. Anything else I can do? I thought that when background activity was disabled, it would not run unless you open it, but that seems not to be the case.