Computer Backup Power - Comments Page 2

An easy way to load test any ups is to first determine the wattage of your load (you can use the nameplate rating on your devices) then substitute a table lamp in place of the load equipment, with a lamp of similar wattage. When the lamp dims or the low power alert sounds, you have the max run time. Figure to use no more than 2/3rds of the time, to allow for a reserve.
A bad battery will die very quickly, often in seconds.

I suggest Bob Rankin writes an article on 'Connecting a car battery to a UPS'
There is a lot to look into. One that comes to mind is the charging circuit within the UPS. If that is taken care of, I should think one would get a lot more HOURS of operation. But I haven't ever found the time to investigate this. If a car battery is hooked up to the UPS without any modifications to the internal circuitry, there is a chance that the battery would fail prematurely.

I have a Cyberpower UPS that doesn't work. I changed the battery in it a few months ago and, as before, when the power goes off, my computer instantly does a hard shut down. So, for me, a ups is a waste of time and money.