First, kudos to you for wanting to protect your sensitive electronics with a good UPS with AVR.
IMO, every computer should be protected by a good UPS.
I personally would be leery of buying off eBay but that's a different issue. Just make sure you can trust the seller.
I have never heard of Vultech so I cannot speak to that. However, the specs of that 800W/1500VA UPS suggest it will nicely support and protect your computer, monitor, connected devices, as well as your modem and router with no problems. I cannot find a spec for the response time, however. I hope it is 10ms or better. I suspect it is.
A couple side notes. The primary purpose of a good UPS with AVR is the AVR (automatic voltage regulation). Surge and spike protectors are little more than fancy and expensive extension cords as they do nothing for low voltage events like dips (opposite of spikes), sags (opposite of surges) or brownouts (long duration sags). And for
excessive surges and spikes, they simply cut power (
“IF” working properly), crashing your computer - never good. A good UPS with AVR will protect your equipment from all those anomalies.
Providing power during a full power outage is really just an extra bonus feature.
That said, during a full power outage, the idea is for the UPS to provide battery backup power long enough for the user to finish typing their sentence, "save" their work, exit their running programs, shutdown Windows, then power off the computer and wait until the mains power is restored. The idea is NOT so users can keep using their computer for extended periods.
A 1500VA UPS is considered large for home and small office applications. That's good. For one, larger UPSs tend to have better specs and nicer features like an LCD status display and support for interconnecting communications. When connected to the computer via a USB cable, this allows you to monitor the UPS status and your mains voltage from your computer too (in addition to the UPS status panel).
Last, remember that UPS batteries last 2 to 5 years and then need to be replaced. This is just normal maintenance. The timeframe varies widely because it all depends on how often the UPS needs to kick-over to battery power, how deep the discharges, and how big the load. I never, as in NEVER EVER buy my replacement batteries from the UPS maker. They always charge more for the same batteries you can find cheaper elsewhere.
It looks like that UPS uses standard 12V 7Ah SLA (sealed lead-acid) batteries. Those should be easy to find from 3rd party sources. Just make sure you get the right terminal sizes. And if me, I would go for 12V 8Ah (or even 12V 9Ah) to give me more battery run time. Note you can always go with a bigger amp-hour (Ah) value, but never smaller. The voltage (12 volts in your case)
must always be the same however.
F1 vs F2 terminal connector size
F1 Terminal – 3/16” (0.187”, 4.8mm) wide
F2 Terminal – 1/4" (0.25”, 6.35mm) wide