5.5. When battery is dead, will UPS still work in standby mode?
No for offline and line interactive UPS 🡪 when AC comes back after black out, the UPS initializes and will stop when detecting no/dead battery. Yes for online UPS 🡪 Once failed AC comes back, the online UPS wakes up with alarm beep. As we know, when UPS is standby, it does not always check battery status. However, when the UPS is turned on or woke up, it goes into self test and detects the status of the battery. For offline and line interactive, most of them are designed to stop working when they find out the battery is abnormal. On the other hand, online UPS usually is designed to run even without battery. Offline UPS does not provide any feature without battery. Line interactive UPS provides only very limited features (voltage regulation) to load without battery. That’s the idea both offline and line interactive UPS always should work with battery only. Nevertheless, online UPS still offer quality power to load without battery, which contributes pretty much to the devices. So, it is still worthy to work without battery.