The battery is not replaceable. It does not come out of the slot at all and the connection method may not allow for easy replacement (I couldn't disconnect it by hand or any other way). It works, but I do not recommend it since the battery cannot be changed (and its design is poor, go for more standard shapes).

Basically, whatever vacation happened, it worked. I didn't leave it until it finished, I closed the devices and then turned it off. It's heavy, some may prefer this format, others may not. The only observation, and of course logical, it emits a little heat from the air vent on the top side. Two UPS sockets, two other simple Surge Protectors. Battery when needed in a few years, I hope to find for replacement.
It's convenient.

Update Feb 2026.
8 years after purchase.
It works just fine so far. The first battery lasted 3.5 years. The second one lasted 3 years. Of course, the second one was 7ah because I couldn't find an 8ah. I replaced the batteries for €15 from Kafkas. The issue is that the end of the battery's life was accompanied by the device turning on and off by itself continuously. The TV that was connected did the same. (I had power as normal). It should have a safety lock for this. I don't know how other UPS handle this issue.
With the second battery, the TV simply turned off and wouldn't power on again. So the previous problem was due to the battery. Anyway, after about 3 years, change it yourself (it's relatively easy, I'm not even a technician and I managed it).
Other than that:
Completely silent. It doesn't have a fan and works with natural air extraction from the vents on its top. I "tested" it during power outages, circuit breaker trips, voltage drops and it works as it should. As for the duration of power supply, I have no opinion, since I only want it to turn off the TV as soon as I hear the beep. It emits a lot of heat at its bottom, under the 4 screws that hold the transformer, not generally. Not that it caused any problem on the furniture, but I wouldn't put it on a doily or carpet. Plus, it gives you a sense of insecurity in case something happens from overheating. Of course, I think this happens with other brands/models too. I put its feet on a wooden block so I wouldn't worry.
The manual is extremely brief. Extremely. It has almost only pictures. It also has a phone cable input/output I think (or ethernet, they look alike and I didn't check in detail) for surge protection, I assume. It has two schuko sockets/outlets for UPS use and surge protection and 2 schuko sockets just for surge protection. When the power goes out, it makes an intermittent sound (beep-beep), which you can easily turn off by pressing a button on the UPS that deactivates it and stops power supply to the TV. It also has a voltage stabilizer AVR, as stated on the manufacturer's website. Very interestingly, the manufacturer's site mentions that it can be screwed to the wall. Very convenient so it's not visible. From what I see, it has suitable slots for this. You screw it to the wall behind the TV or under the desk. Very practical so it doesn't take up space and isn't visible.
In the end, reading generally that in the UPS category there are many complaints for all brands, I would say it's probably a good purchase. I mainly focus on the fact that in every outage, breaker trip, voltage fluctuation it responded perfectly and protected the TV.
https://energenie.com/item.aspx?id=7609

Positive:
- Design that fits on a desk. That's why I chose it.
- 4 sockets (2 for simple voltage protection, etc. and the other 2 function as UPS and protection)
- Phone protection
- So far, it has worked perfectly during power outages and in 2-3 "tests"
- 850VA ideal for this price
- Immediate response from Gembird when I searched for information (Dutch company)

Negative:
- The user instructions are so few (in image format, without captions) that I had to contact GemBird for information.