UPS 1800VA/1000W Lifespan: Usage with 5 Computers, Duration & Data Saving Process Explained

I have a 1800VA/1000W UPS
5 computers connected to it
how many minutes will it last without power
can you calculate it?

I understand that the computer to which the UPS is connected after the power is cut off, the system saves the data and turns off the computer?
and the rest of the computers have to be turned off manually and save the data beforehand?
does it work like that?

It will automatically turn off the computer if:
1. the ups monitor program is running, e.g. connection via usb and ... in windows in 'power options' is set
2. several computers can be controlled (i.e. ups or host computer sends a signal about power failure) via LAN
3. 1800VA for 5 computers is very little: 1 computer currently has a 350-500VA power supply so it's easy to calculate, add a monitor... and 1800VA is not enough!

It can only be calculated in an approximate way, but you need the capacity of the batteries used in the UPS. If, for example, it is built of two 7Ah batteries. This is an approximate, theoretical capacity excluding any losses is 2 * 12V * 7Ah = 168Wh. So if your 5 computers draw together about 1000W, that's 168/1000 h = 10 minutes. I repeat once again that this is just a theory, the converter is a lossy system, the current is not in phase with the voltage, etc., so the time may be significantly shorter. Your computers may also download less while you're working, which will increase that time. Probably just do a test, turn on all machines, run typical applications or games on them (depending on what they are usually used for) and wait. Also note that your UPS has only 1000W and heavily loaded computers can draw more from the network, even 300W (+monitor). At the same time, heavily loaded computers will cause that in the event of a power outage, the UPS will not work at all, it will indicate overload and turn off. I would recommend buying a more powerful UPS.

The backup time of the UPS depends mainly on the capacity of the batteries.
Typical small "pigs" have 12V 7 Ah batteries, larger rack batteries usually have a battery with a capacity of 14 or 21 Ah and a voltage of 24. Large UPSs have batteries with a capacity of tens or hundreds of Ah, often external batteries with a voltage of 36, 48 or 60V.
If we have a small UPS with a 12V 7 Ah battery, a 300W load will discharge it in about 10 to 15 minutes