Oh boy. Where do I begin with this article. Let's start with: Happy New Year!

Okay, maybe a table of contents is a better start:

One preface before we begin:


I'm not saying I'm qualified. I'm not. But I have a decent idea of what I'm doing and have lots of tools, paranoia, and people to consult to guide me through it. Also - since I'm posting this for internet scrutiny, you, dear reader, can email me if I have done something dumb (at 7666@lain.la)!

Okay, without further ado:

The Problem

As you may or may not recall, I had a generator project in the works over on the begging donations page over here. This was designed to provide Lain.la's full 1kW power requirement with the ability to tolerate an extended power outage, with the inclusion of a 15kW propane generator and automatic transfer switch into my home's electrical system. This idea was great and all, but came at a price tag of nearly $16,000 for labor, parts, the generator itself, permits, gas lines, the ATS, etc etc. This was simply too costly to run and maintain. I don't need my whole home powered, and I don't need a $16k hole in my wallet. But - my current UPS systems can only run Lain.la for a maximum of 15 minutes before they start failing.


This was the conundrum that I couldn't quite figure out. I had some options:

  • Wait a year or two to work up the funds to buy the generator.
  • Wait a couple years and put in a whole solar system with solar batteries at a cost roughly 3X the generator.
  • Do nothing and if Lain.la fails, whatever. Not like I charge for these services.
  • Find another way.

Indeed - all the options sucked. Waiting didn't solve any problems, and accepting the risk of a power outage really weighed heavily on me. I had to find a solution for option 4 that met the following basic goals:

  • The idea can't be too expensive.
  • It has to work seamlessly - no human intervention.
  • Don't burn down the house.
  • Provide power to run all systems for at least a few hours.

As far as I'm aware, there are no commerical UPS systems, outside of Cyberpower's EBM compatible UPS systems, that can do all of this for cheap. You could buy a PR1500RTXL2U with 3 BP48VP2U02 battery modules, but you're looking at $3000 for less than 2 hours of runtime at 1kW. Not gonna cut it.

The Plan

After searching and striking out on off the shelf solutions, I had an idea. What if I bought most of the components of an off-grid solar installation, and just didn't buy the solar panels? What if I ran the batteries on AC, and had the system prefer AC power? It turns out - This is kinda what people with RVs do! The concept is simple: You have an inverter (device that turns DC power from batteries into usable AC power for regular power consuming appliances) that prefers "Shore Power". Shore Power is a term used in the boating business to refer to power you get when docked at shore so you can turn your power generating engines off - but RV'ers sort of stole the term for when they're parked at a place that offers a power plug so they don't have to run their engine. I'm going to steal the term to just refer to an outlet in my own home. Then, if this perpetually connected shore power fails, it will switch to the DC batteries, just like a UPS.

The concept of a power system for an RV looks like this:

Where my design differs from this RV setup is simple:

  • The entire Green side of this system is gone, minus the batteries.
  • The entire Blue side of this system is gone.
  • The Yellow side is just a wall socket in my house.
  • The Red side is the Lain.la systems and servers.

The Build

So, with this concept in mind, I came up with this:


This, ladies, gentlemen, and enbys, is the (new v1.1) diagram for the Lain.la DIY UPS system. It's a beauty, despite the abuses of electrical diagram symbols. So, a quick breakdown:

  • We're using 2 CHINS 12.8v 300Ah LiFePO4 batteries here for our battery power, in parallel. That's 7.68kWh of storage!
  • I'm using a SunGoldPower 3000W Inverter/Charger/ATS combo box as the central unit in this system. It handles inverter, charger, and transfer switch duties, making this build very simple. It's basically all the brains of a traditional UPS, minus the batteries. The transfer switch delay is basically nonexistent too.
  • The Bank A/B UPSes are my Cyberpower 1500VA PFC units. I'm re-using those in the system - that's what gave me battery power for quick power interruptions before.
  • The Shunt and Inverter monitor provide a really nice graphical display of the system. Pic below!

And for some FAQ stuff:

  • 2/0 AWG wire is more than sufficient for what I expect to be, at worst, 100A of draw from the batteries. We're only powering Lain.la, and it pulls a very consistent 1kW. I'm assuming 200W for conversion losses from DC to AC. I did a test run of 1.4kW using a resistive load (a heater) and that pulled 125A from the batteries. The wiring got a little hot (80C at the fuse after 1 hour) but nothing outside of the spec sheet ratings.
  • I have a camera, spare fire extinguisher, temperature/humidity sensor, and smoke detector for safety reasons.
  • I'm using 3 12AWG extension cables for the AC input and AC output side. More than capable considering the loads. 12A of AC load (8A for Lain.la, 4A temporarily for battery charging) on the input, and 5A or less on each output.

This was not a cheap project, but considering the generator price, this was a perfectly acceptable alternative. Here's the cost breakdown:

  • Ampper Battery Switch - $13.99
  • 2/0 AWG EPDM Insulated 3ft Cables - $42.04
  • 2/0 AWG EPDM Insulated 1ft Cables x4 - $91.44
  • Plastic Drop Cloth - $6.79
  • Smoke Detector - $18.95
  • REOLINK 4K Security Camera - $101.99
  • GoGreen Power 12AWG Extension Cord x3 - $66.00
  • Genuine Joe Rubber Mat - $56.62
  • CHINS LiFePO4 300Ah 12V Battery x2 - $1,939.98
  • Sungoldpower 3000W DC 12V Inverter/Charger/ATS - $825.00
  • TopstrongGear Brass 300Amp Fuse with Holder - $12.99
  • Fastronix Terminal Covers x5 - $42.45
  • GE 6 Outlet Surge Protector x2 - $29.98
  • Renogy 500A Battery Monitor with Shunt - $61.99

Grand Total: $3,310.21

Sounds like a lot, until you realize it's 1/5th the generator project.

Final Results

So, the system is now fully completed. It took quite some time to build. I placed it in my generously sized crawlspace, after putting down a big rubber work mat and stapling some plastic to the ceiling (should the insulation ever fall down - don't want THAT on the batteries). I haven't transferred the servers to it yet, but I expect to within the next week after I test charging, discharging, safety, heat, system behavior, break-in period, etc. It works as I expected it to so far, and I'm only minorly injured from a small drill incident.

With this system, Lain.la should be able to run for 7 hours+ on battery!

Ok, so it's picture time! Oh, and the security camera footage at the bottom makes the whole thing look worse than it is. Blame the lighting.

NEW: Improved output side with enclosed 20A breaker for safety:

I hope you enjoyed this article. I'm going to chill out on changes and projects in 2023 now that this is done. I've spent too much time and money as it is.