dc ups

3 Articles

Second Life UPS Mark II: A UPS For Low-Voltage DC Applications

December 17, 2023 by 17 Comments

When you have a whole stack of devices and appliances that all have an AC to DC adapter and which you’d like to put on an uninterruptable power supply (UPS), you could do the obvious thing and get an off-the-shelf UPS with myriad AC outputs. In the case of a 19″ rack this means wrangling a power strip or two and any combination of differently sized AC/DC adapters into the rack, with questionable efficiency and waste heat dumped into the rack. This is where a DC-only UPS like [Maciej Grela]’s Second Life UPS Mark II provides an interesting alternative.

At its core it’s a pretty simple concept: A single 400Watt power supply handles the AC/DC conversion from mains to 24 VDC, which feeds the battery charger as well as the outputs. These outputs include 5 VDC, 12 VDC and Vrail, with the latter being either the output from the PSU, or the battery voltage. In case of AC power failure, an LT4416 dual power path controller handles the switch-over from the PSU output to the internal batteries. In the article, [Maciej] covers how the buck modules for the 12 & 5 VDC rails were sized, along with the conversion of an old rack-mounted network switch into a UPS. Continue reading “Second Life UPS Mark II: A UPS For Low-Voltage DC Applications” →

Breakers for the system on a DIN rail, with markings like 48V and 24V and 12V and so on on the bottom, and two hefty devices of some kind on the bottom, probably MPTT controllers, with hefty wires running from them.

Low-Voltage DC Network Build Incited By Solar Panels

November 2, 2022 by 51 Comments

Nowadays, some people in Europe worry about energy prices climbing, and even if all the related problems disappear overnight, we’ll no doubt be seeing some amounts of price increase. As a hacker, you’re in a good position to evaluate the energy consuming devices at your home, and maybe even do something about them. Well, [Peter] put some solar panels on his roof, but couldn’t quite figure out a decent way to legally tie them into the public grid or at least his flat’s 220V network. Naturally, a good solution was to create an independent low-voltage DC network in parallel and put a bunch of devices on it instead!

He went with 48V, since it’s a voltage that’s high enough to be efficient, easy to get equipment like DC-DCs for, safe when it comes to legal matters concerned, and overall compatible with his solar panel setup. Since then, he’s been putting devices like laptops, chargers and lamps onto the DC rail instead of having them be plugged in, and his home infrastructure, which includes a rack full of Raspberry Pi boards, has been quite content running 24/7 from the 48V rail. There’s a backup PSU from regular AC in case of overcast weather, and in case of grid power failures, two hefty LiFePO4 accumulators will run all the 48V-connected appliances for up to two and a half days.

The setup has produced and consumed 115kWh within the first two months – a hefty contribution to a hacker’s energy independence project, and there’s enough specifics in the blog post for all your inspiration needs. This project is a reminder that low-voltage DC network projects are a decent choice on a local scale – we’ve seen quite viable proof-of-concept projects done at hackercamps, but you can just build a small DC UPS if you’re only looking to dip your feet in. Perhaps, soon we’ll figure out a wall socket for such networks, too.

DC UPS Keeps The Internet Up

November 1, 2021 by 33 Comments

We occasionally get annoyed that so much gear takes the ubiquitous “wall wart” these days. But one advantage is that the devices operate on DC voltage. [TechRally] takes advantage of this to create an automatic DC UPS with dual outputs to power a router and modem in the event of a power outage. You can see two videos about the project below.

Some may say it would be better to use conventional UPS, but think about it. That UPS has a battery in it that gets converted to AC so the wall wart can convert it back to DC. Each conversion loses some energy, of course, and in the case of a cheap wall wart, you may even lose quite a bit.

The project contains eight 18650 batteries, an off-the-shelf charge controller, and power converters. Could you do a more efficient custom design? Maybe, but the use of these inexpensive and commonly available modules makes it quick and easy to pull something like this together.

No one would mistake this UPS for a commercial unit, but it does have a certain hacker aesthetic. We wouldn’t carry it through an airport, though. With those digital displays and all the wiring, it looks like a bad TV show’s bomb prop.

If you don’t care about the automatic switchover, we hear that 5V will power a lot of equipment these days and that makes battery operation as simple as stripping a USB cable. This could probably drive some other gear like a connected Raspberry Pi. Or, you could do that job with some supercaps.

Continue reading “DC UPS Keeps The Internet Up” →