Battery powered PC server for radio project

[fergusonnn]

Basic background.. I have 6-8 small computers running in different locations that stream the local railroads as well as decodes the radio codeline (radio transmissions used to control signalling, switch position, track occupancy, etc)..each server consists of a cellular modem, standard Dell PC, and 2-4 two-way radios running off the +12v rail of the power supply (not ideal.. I know.. but it's worked fine on my servers for over a year and a half now)

Most of these sites are at remote radio towers on mountaintops which require the tower company on site to access, and are prone to power failures which can cause the computers to hang up and freeze while rebooting. Originally I was thinking about just taking a good quality UPS and modifying it for extended runtime using car batteries, but I feel like that would take a lot of work and reduce the efficiency of the setup. I'm deciding to try a different route. Instead of standard computers connected to AC, this is what I'd like to do..

- Mini PC converted to run off 12v DC power from battery
- Sealed car battery with charge controller that will allow charging/power from AC supply, then change to battery power during power failure
- Add a solar panel and charger/controller to keep batteries maintained during extended outages

While this may seem overkill for a project of this caliber, my goal is to reduce downtime due to power failures and such, while allowing the systems to continue operation during extended power outages.

I'm mainly looking for assistance with recommendations for Mini PC's to use. Price is of course a big factor, since these are not a profitable operation. However, they do not have to be super powerful. I was given Optiplex 380's by a friend of mine to use, and they run Core 2 Duo's with 4GB RAM, which is way more than what is needed (the original servers we used were Compaq Ipaq's with Pentium III processors.. if that tells you how little processing they require).

Right now, I have been looking at a Mini PC from Amazon, from a company called ACEPC.. $99, uses an Intel x5-Z8350 processor, 2GB RAM and 32GB of storage. (Warning, the description translations will make you cringe) https://www.amazon.com/dp/B07D9YX3W6/
 

I've read through the reviews, and a lot of them seem positive considering the computer and price point it is at. From the photos though, it doesn't look like I can go straight +12v into the computer, so I'd have to find a way to go from +12v to +5v.. have to see if it's an AC adapter or what would need done. I'm looking at other options as well, like some from Zotac, as well as some used options. Any suggestions on Mini PC's, or any tips/tricks for the power solution I'm working on?