DC as a supply to equipment

There are plenty of devices that use DC to power them. However in forums I find people are dismissive of this option. The holy grail appears to be inverters with large battery banks…

I suppose it really depends on what equipment you want to power with DC, and the DC voltages and currents involved. I wouldn’t recommend powering equipment in your home with high voltage DC which could be dangerous, but network equipment etc. that uses 12Vdc should be fine.

All of my routers, alarm system and Intel Nuc (running Home assistant) runs of a 12Volt bus. My POE switches and camera’s runs off a 48volt bus. All directly from my 48Volt battery bank. (12 Volt from a 48Volt to 12 Volt DC Converter)

I initially started with a pure 12v system, distributed through two houses. Two 100w solar panels, with an EPever MPPT charger and two 100AH batteries in the garage.

This was powering multiple 12v lights for both inside and outside. Also the various routers and multi 12v charge sockets in each house, used for cellphone charging.

I dont think this is entirely true, people that normally comes to the forums are in the market for bigger backup systems and to them MicroGrids and devices to keep their routers live is just not an option, they normally have much bigger plans and use the 48volt backs to create DC supplies to other equipment.

I wouldn’t say people are dismissive, at least not without good reason. I think anyone who understands this business knows that a DC setup is more efficient and costs less, but what fewer people understand is that the equipment (cabling and switching) costs so much more.

I grew up on a farm in Namibia where our lights were a 36V DC system. You can imagine that we had many many 60W lamps (they were technically 32V lamps), so each one would draw a good 2A. At some point some shop in the nearby city started making 36V flourescent lamps, and those were excellent cause they only drew 20W!

So I relate that story just so you know that I fully understand how well DC can work. However… since it was a farm, and since farmers are rarely acquainted with grid codes, I can also tell you that installation would not pass. The switches for the lights were normal AC-rated units, and most of the light wiring was done with normal 2.5mm^2 wiring (for perspective, the battery bank was anything between 200Ah and 1000Ah in later years). There was a DC-rated breaker on the other end, cause Hoffberg made a whole kit back in the 70s with a generator and a DB board that farmers could just install. So there was some safety…

Now imagine doing a DC install in a home today. In a city. Complying with grid codes. The first issue is that you cannot have AC and DC in the same raceways, so get out ye olde angle grinder, ship the wife to a hotel (cause she is not going to like all the dust), and start chasing new paths for your conduits. Then find DC-rated switches for everything, with all the cost related to that. Then imagine what happens if you sell the house one day, and you decide you’re taking your expensive batteries with you, and all of it has to be returned to AC-spec.

Pretty soon a good old inverter – efficiency be damned – just looks like a heap less trouble.

What I will say however, is that low power DC-bus solutions, for example PoE, is an excellent solution, and one I can wholeheartedly recommend.

Indeed! I attended a webinar a few years ago on the emergence of DC standards.
The voltages they indicated as standard are: 5V, 12V, 24V & 48V (Above 48V is another class which is considered dangerous and requires qualified personnel to work with it)
In my time I have seen 6V, 9V, 19V etc.
Clearly the USB standard has made its mark!

I do like my DC as well.
I think that the buzz in the media is all about inverters, so that also contribute to many people not thinking about a DC option as they don’t know about it.

I am curios to know what cables you use for a DC bus in your house @JacoDeJongh @Deon_in_ZA ? Are those POE ethernet cables or something bigger?

The next question would also be if the POE will conform to the DC SANS requirements. Most I have seen are not in ducts or labeled.

Most of my cables are 6mm with around 35 meters length, from the garage to the first house. So voltage drop there is around 3.6% if I were to use up to 10A. I only have around 25 meters to the second house, so even less voltage drop. Each line out only has 4A automotive fuses.

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Yeah, I THINK I know what you are referring to… saw that too, if we are on the same page.

Mine is 4mm and max lengh 12m. My POE is eathernet.

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This is clearly an issue with DC reticulation. The only heavy current connectors I have noticed are the Anderson range.
What I see with the smaller supplies (e.g. power adapters) is the 5.5 x 2.1 mm barrel plug becoming a standard. Pretty much all ONTs have these plugs so I reckon that will become a de facto standard (with 12V as the supply voltage)

Rechecked my old 12v system last night, and although it starts out at 6mm, it only stays 6mm for about the first 6 meters. Thereafter it drops down to 4mm as well.

My first junction box on my side is 15 meters, with an 150A Banggood watt meter and analyser, mainly just to check voltage and amps drawn. On my daughter’s side, I only added the multi 12v sockets, for basic phone and tablet charging.

What are you powering with the DC wiring?

On my side, I have 4 sets of 12v LED remote lights outside, 3 inside as well as always on LED lights in our snake room, plus the wi-fi repeater. On my daughter’s side, she has 7 LED lights throughout the house. Two are dimmable, for the kids rooms. Also has the fibre equipment and main router on her side, on the 12v system.

After Jaco installed the Goodwe inverter, I left the 12v system in place, so I can still access everything in case the inverter has issues during load shedding.

… fokolie DC other than on the Victron stuff. :laughing:

I think there are difficulties trying to reticulate DC wiring what with no available fittings to help you, not to mention the thick cables if you want to draw any current.
However if you move down the order to ‘mobile’ devices these all run on a battery which supplies DC. From your laptop to cellphone to any widget that requires power this will be provided by a battery. This makes a lot of sense since there is no reticulation required and it’s no accident that this is the way it is.
To be continued…

Typical modern electronic components require 5V and 3.5V
However these must be regulated so the supply voltage from the power adapter is typically 12V which allows plenty of headroom.
Even 12V LED lighting doesn’t require 12V exactly. LED drivers are constant current so as long as the required current is achieved the voltage isn’t critical.
This gives you an idea of how low the voltage that is required to power electronics.(which makes 220V look like a total overkill which it is)

Again some feedback from my 80s farm background.

For higher DC-power applications, in my experience, the watershed moment is when you discover you need a refrigerator. One that is larger than the average camping type, or the cheap peltier coolers. There are refrigerators with DC motors, but they are usually built locally, they are expensive, and they often don’t last. I saw one on a Karoo farm a few years ago. It was a 12V refrigerator, about a meter tall. It was noisy too.

In any case, this was the wisdom of my father back in the late 80s. He said that because your “dorpsyskas” (city fridge) is so much better in terms of quality and longevity, the correct thing to do is buy the most efficient one you can find (which back then meant AEG, or Bosch if you couldn’t find an AEG), and an inverter.

Once you pulled the trigger and installed an inverter, the rest of the debate becomes less heated. In our case the lights remained on DC, because it was on DC before the inverter arrived. On the neighbouring farm the lights remained on AC, because it was on AC before the inverter came.

Indeed! Since the DC option is so untested it brings up these issues which you stumble on as you proceed down this path. That said there is no doubt that the regulators are bringing pressure to bear on manufacturers to standardise their plugs and voltages. (witness the mobile phone industry that has been forced to use standard plugs for their phones)
Even the PC laptop vendors will be driven down this road. (I saw a new Dell laptop recently that was being powered by USB C)
Regarding fridges we are seeing progress: Defy hybrid fridge freezer