The output wave most likely. It has to be a sine wave and CyberPower supposedly has simulated sine wave… I’m scratching my head at the moment…
Oh man I remember back in my reefing days hearing that battery backups are not good for aquarium equipment... I am trying to remember why for the life of me, has something to do with the way the battery delivers the power or something. I'll do a little research, see what I can find.