Newer WiFi 6 routers tend to have fans cause they get fairly warm but I’ve had a ups on mine for literally years and had to replace the battery in it once but before I got one even I still never had that problem we haven’t had a power outage in like a year or 2 now and I maybe happens once a year if it does so I don’t see your problem and I have it set to auto turn back on when it gets ac power so it’s a non issue