Server power

Presumably, you need that much horsepower -- even in the absence of mains power? (I fall back to slower devices that draw very little power for longer uptimes during outages; *this* machine, router and modem won't last more than 3 hours in such cases)

Some of the NUC models have respectable performance:power ratios (I'm building a pair of media servers with some older i7's as I'm typing this)

You'll also have to consider what your display(s) cost (in terms of power). Or, is this truly a headless server application?

Do you think an automotive battery charger will be more effective than the charger in a UPS? I.e., why not pick up a scrap UPS and just add your batteries externally (many have Anderson connectors for that express purpose -- either internally or externally "for expansion")

I plan a similar approach (but with a 48V battery pack) as the power source for my PoE switch using solar as the primary source into the pack and a considerably smaller mains powered "charger" to keep the (reduced) load up in its absence (but, I have already planned for a large variation in "battery voltages").

And, will be moving my "farm" to an outbuilding with separate solar power (fiber to a display cluster in the house).

Economics is also a factor. I might parallel two batteries if necessary. Since that charger unit and a 12V lead-acid car battery are popular items, they are not hugely expensive. It would be unusual in this area to be without main power for 24 hours but not impossible.

Hard to say but it seems like a reasonably simple solution.

I meant "computing power" available during a power outage. I usually scale back my needs during outages (but our outages have never exceeded 4 hours) -- email, etc. instead of any real "work".

Do you have to worry about out-gassing where it will be sited?

I would look into maximum input voltage that the PC can tolerate and make sure the charged battery never exceeds that -- as well as the *charger* output (in the absence of a battery load).

You haven't said but I am assuming you are running it headless so no need to power anything else (monitor, printer, etc.) off of mains (in the *absence* of mains).

I am lately seeing UPSs with lithium packs. But, unaware of what the cost effectiveness would be for your storage needs.

Probably not but good point. That reminds me of watching a video recently where the presenter said the atmosphere is about 78% nitrogen and 21% oxygen but the subtitles said 78% hydrogen and 21% oxygen. I've got the matches locked away.

Yes that's a good point too. If I do this I'll watch the battery voltage in all charger modes to make sure it's not more than might damage the computer. A series diode or two could be added but it wastes power.

Yes just Linux servers. No display needed after setup.

There are other things with displays but they have their own 115V AC UPSs.

And at "high line" as the charger may be little more than a hefty transformer with diode bridge; if line voltage climbs, so will the output voltage.

OK, so having backed up mains power available isn't an asset. You may also want to look for a noname display that will run off

It is annoying how often one has to drag out a monitor to see what the server is trying to tell you (regarding why it won't boot). I've taken to "storing" monitors near servers with multiple servers cabled to a single monitor (using the "input select" on the monitor to determine which output I need to review). I figure it's a bit more of an eyesore but takes up the same amount of space whether it's being "stored" in a closet vs. adjacent to a set of servers!

Yeah I had that not long ago when an old dell laptop with hard drive replaced with ssd and broken display went into kernel panic just because I pressed the power button. So I needed a display on the VGA port to get it going again.

I have a tiny little box that provides my core network services (DNS, TFTP, BOOTP, fonts, etc.). It "hides" under a dresser as, for the most part, "it just runs". I used to keep a 9", 12V display plugged into it but the display was more of an irritant (where to put it?) than an aid.

I started getting complaints from SWMBO about "the printer being broken". Or the scanner. This invariably was the result of BIND not running (easy to verify by pinging IP addresses instead of hostnames).

Problem was always that the little box had powered itself off (evidenced by the super tiny LED not being lit). Reapply power and all is well.

Until the next time.

Eventually (by making time to actually INVESTIGATE the problem), discovered that it wasn't plugged into the UPS that I had placed there primarily for it's use! (I had taken advantage of the UPS's presence to power a couple of 1U servers that also hid under furniture -- but, neglected to plug the little box in!)

I've since added a monitor so I can power THAT on to see if the little box is alive (instead of getting on my hands and knees to check the power indicator on the little box!). And, a wireless portable "toy keyboard" so I can interact with it without having to make space for a real keyboard.

Of course, I could also have configured the little box to power itself back on when power returned but I always fear glitchy power bringing a box down, then up, then down, then up... so have every machine set to stay "off" after power fails.

That method is okay, but somewhat dated these days. Backup solar "generators" are all the rage. Anker SOLIX has units designed specifically for UPS backup with fast switch-in times and pure sine wave inverter. For solar, you only have to plan for a 16 hour blackout before recharging, which is a major simplification.

You can use the SOLIX to float charge your car battery through the Schumacher and not the other way around.

Google-AI:

Essential Technical Requirements

Pure Sine Wave Inverter: Only use generators with pure sine wave output. "Modified sine wave" inverters can damage sensitive computer power supplies and components.

UPS Functionality: Look for units with a switchover time of 20ms or less (like the Anker SOLIX C1000 or Jackery HomePower 3000) to prevent your computer from rebooting during a power transition.

Battery Chemistry: Prefer LiFePO4 (LFP) batteries. They are safer for indoor use and typically last over 10 years (3000+ charge cycles) compared to older lithium-ion models.

I think the point was to eliminate the need for a backed up mains source as the PC seems to have been /specifically/ selected to run on a typical battery voltage.

Google AI has this to say about that situation (not necessarily better or even feasible):

1. Industrial Solar-Integrated UPS For remote or industrial sites, integrated systems combine solar panels with DC-native UPS components.

Solarcraft Hybrid Systems: These Hybrid Solar & UPS Systems are designed specifically for remote electronics like PLCs and radios, combining solar power to top off batteries when utility power fails.

Solar Electric Supply (SES): Offers Outdoor AC/DC UPS™ Systems in NEMA enclosures. While they list 24V systems, these are often adjustable or available in 28V configurations for specialized microwave and private network sites.

United Tel-Supply VOLTAR 2.0: A specialized Solar UPS designed for off-grid SCADA and wireless equipment.

1. DIY & Component-Based Setup

If you are building your own, you can create a highly efficient DC-coupled system.DC-DC Charge Controller: Use a solar charge controller (like those from Renogy) to charge a 24V battery bank. Most 24V lithium (LiFePO4) or lead-acid systems naturally operate near 27.2V–28.8V during charging, which matches your 28V requirement.

Voltage Regulation: If your computer is sensitive to voltage swings, use a Wide Input DC-DC Regulator (e.g., from Newark Electronics) or an M2-ATX power supply which can handle inputs from 6V to 28V DC.