USB Power Delivery

I have an idea. It is not mutually exclusive to tiny homes and I don't think this will greatly benefit people with grid power or large power generation systems. The idea is that many things run off of low voltage DC power and the number of devices using this type of power is increasing. Or maybe it would be more correct to state that many higher voltage AC devices step down that power to DC and a lot of devices are on the verge of putting a USB connector between this step-down converter and the device.

The new specification I came across several weeks ago is USB Power Delivery (USB PD). This specification has several profiles, the highest of which allows for substantially more total power to be drawn. This can remove many of the region specific high voltage power cables from typical computer systems (and countless other devices) in favor of the Universal Serial Bus (USB) connector. Having power conversion devices for your home and vehicle will allow you to power and/or charge a myriad of existing devices, with vastly more devices on the horizon that can use a versatile standardized plug. You can already find many power adapters and device that provide USB power, and I believe it is inevitable that billions of new devices will roll out over the next few years utilizing newer USB specifications.

For those with large power generation sources, it will be as simple as plugging in an adapter. There are probably many people with tiny homes that run high voltage cables through the walls and wouldn't consider anything less. But for those going off-grid and looking to maximize efficiency, I think the new USB-PD spec is worth serious consideration. Given that the standards are already published, it would be very easy to run wires and even provide the power needed to run these new devices during the early building stages of a tiny house. The minimal extra cost and labor to do so could pay dividends as opposed to omitting it and wishing you had done it after the fact.

The USB PD Wiki Page shows the basic table of the MINIMUM power outputs of each voltage requirement for particular power profiles. After digging through the information from reference 100 of that page, I found the minimum requirement for any of the power delivery cables is 5 Amps. Given the inexpensive nature of wiring a tiny house, it would probably be worthwhile to go above and beyond that minimum. Also noteworthy from the documentation was that while the 5V, 12V, and 20V minimums must be satisfied to meet a particular profile, aftermarket power supplies may include additional voltages as they see fit. These would be ancillary to the USB PD standard profiles. I doubt you would find too many devices using more than a few voltages on any single device, but it wouldn't hurt to add an extra pair of cables if you are running wires depending on the situation.

Even if this seems a bit over the top, many devices today are already exceeding previous USB power standards. Providing a steady power source of 5V 3A will meet the maximum power requirements of the USB Type C connectors that have been equipped on newer devices over the past several months. This doesn't have to be a complex installation. I added a car USB phone charger to my solar PV setup by opening it up, soldering wires and connecting them to my charge controller. There are many voltage converters out there that can accomplish the same goal without any soldering. Once USB PD becomes the norm, similar voltage converters will be every bit as easy to find. If your tiny home is prewired for it, then it could possibly be installed in a matter of minutes.

The one thing I think about with the new USB PD spec coming out is all of the non-computing devices that will come with it. Think of all the different lights and fans and battery chargers available that can plug into the current 5VDC USB connectors. The new wave of items powered by USB PD could easily cover most of the needs for a tiny home or other off-grid area. The more things you power directly from DC with an off-grid power source, the smaller or fewer power inverters you will need. This can be a savings of energy and money. I hope this gives people some food for thought.

Daniel -

I agree with you 100%. With LED lighting and DC powered refrigerators now available, I don't see why anyone that wants to go off-grid is installing large solar arrays with equally huge inverters. They are losing a ton of efficiency switching from DC to AC and back to DC for simple things like running their DC laptops and phones, and they could further improve their efficiency by running other devices off DC where possible. Years ago I had wanted to wire my house with DC, but this was long before USB was publishing standards for power like in the spec you posted.

AC is good for high power going long distances, otherwise there would be way too much transmission loss on the wires. But once in the house (or if the power is generated locally), I think there's a huge opportunity to go DC in our homes with very small inverters for those devices that need AC. This isn't practical for the average American running their AC at 65F year round and 3 big screen TV's on, but for tiny homes or homesteaders it's totally possible.

it makes sense...

in our tiny hut (completely off grid, some 12V PV) i ll install 12V DC jacks, like the one in cars for cigarette lighters. a 2,1A usb connector for these comes around 1€ here. 12V DC will give more flexibility (LED lighting, 12V equipment, small inverters, charging older laptops etc.). where usb power is needed, i could install double jacks and put usb connectors in it.

i like the flexibilty of 12V with a small inverter. there are many appliances that run on 230V AC but have below 50watts. like a fan, a charging-thing for a laptop, soldering iron, charging thing for electric drill. this is easier than to run the generator for these small things.

there are fridges that run on propane. so there is little use for most 230v AC appliances.

Thanks for the replies. I think one of the main issues with using DC power ports has been a lack of standardization. It causes fragmentation which can make things more expensive and inconvenient. I agree that many people will benefit from having cigarette lighter jacks in an off grid situation, but I wish they weren't the norm. They are massive connectors with connection issues that can cause increased resistance or a complete lack of connection. They were made for cigarette lighters to fit inside.

I'm hoping the new USB PD standard will be expanded in time to handle 10 Amps like typical cigarette lighter circuits in cars. For something more powerful, the XT60 connectors are cheaper and much higher current capacity than many other options out there. They seem to be popular with the RC crowd. I'm thinking of using these and making a couple of break out cables to go from XT60 to a cigarette lighter, with an appropriately sized fuse built in of course. I think these XT60 connectors will be particularly useful when installing some permanent DC appliances, since it will be easier to work with as opposed to hard wiring something in place with a junction box. It would also be really nice for something like this to be molded into a receptacle for use in standard electrical boxes. This would make for a clean and easy installation that would be more easily accepted by governing bodies.

It doesn't necessarily have to be the XT60 connector, but something with similar properties that could become standardized would make it easier and safer to install and use. Until the USB standards start to catch up, it wouldn't be a bad idea to have a tiny home prewired for it and use something like XT60 connectors.

you could use 230V or 110V (or whatever you have there) plugs and sockets and connect them to the 12V devices. you could wire your tiny house like you would with 110V or 230V and connect that to your battery-bank or charge-controller. it would work in most situations, some situations would call for a higher wire-diameter.

another advantage of 12V is that you can use 12V car fuses as protection.

but the xt60 connectors look like they shoud do a good job.

Using automotive fuses is an excellent idea. You can even use a fuse block from an old car as your fuse box. There are some screw down types that would be easy to use for making a custom fuse box. Plus you can go to a junkyard and get a lifetime supply of fuses for just a few bucks.

I have used standard household receptacles and plugs for a quick fix, but I think it is a bad idea to implement in a tiny house. For one, anybody who doesn't know any better will just try to plug something in that isn't meant for it and could blow fuses. The biggest problem for me is the price. I can cut cords off of things and I have a box full of old receptacles that I can use, but I save those for other projects. The XT60 connectors are rated for higher amperage DC at a cheaper price. I have also used standard household light switches, but they are not made for DC and if you draw a lot of current across them and use them frequently then they can burn out much faster than they would using them with AC.

There are lots of places to draw inspiration from and reuse existing hardware. I guess for many people building their own PV power system then they are familiar enough with what they are doing that they can get away with things that other people would surely have problems with. I'm just inspired by the whole USB connector situation where it works great at what it does and is the same around the world.

yay ... i wonder if there comes a time when people will charge their electric drill via USB. it might happen. i mean, things are being build for USB that weren´t when USB first came out.
atm i am looking to buy loudspeakers that are powered by USB to connect to laptop or mp3 player. it makes more sense than transforming 12V DC to 230AV and then to maybe 6-10V DC for the loudspeakers.

I have been using one of these - DROK 3W + 3W Amplifier. It isn't going to be enough for a block party, but certainly enough for me out in my shed. I used an old USB cable for power and an old headphone cable for sound input. What is really nice about that device is the size. The knob I put on it is bigger than the whole unit! Roughly postage stamp sized with a small potentiometer. A pair of Sony satellite speakers someone was throwing away work well for my needs, and I couldn't beat the price.

I had previously bought another sub $10 amp for a car that I had directly connected to my batteries powered by the sun. It worked fine but had an annoying color changing LED light inside. I eventually gave that to my mother and hooked it up next to her bed as a headphone amplifier for her TV, after removing the LED of course. It worked as well as could be expected for the price.

I definitely can't wait to see 12V USB power become common. I have been using cheap automotive interior replacement LEDs for task/emergency lighting. I have run a pair for a couple years straight and they still appear like they haven't degraded significantly. They draw 4 watts at around 14 volts, so you could hook up a bunch of them in parallel on a USB cable that can handle up to 100 watts. It would be pretty nice to have USB ports in your ceiling to customize your lighting on a whim. For some reason I have be really enjoying making my own light fixtures out of stuff most people would throw away or recycle.

I don't much like the idea of using AC sockets for DC, sounds like a recipe for accidents to me.

Daniel, I like the idea of the XT60s, I'll have to check those out. I'm intrigued by the possibility of a lower priced connector rated for a higher amperage compared to the Anderson connectors I used currently.

OTOH the Anderson is well designed as far as self-cleaning and maximizing life by minimizing arcing.

I really like Anderson connectors, they just get pricey when you want to put them on every damn thing. I've got some salvaged SB175s that I've used for a few different applications, and a bag of PP45s for smaller stuff. I like the SB design better in use, but the PP style is more flexible.

AC sockets would work. but they re not designed to handel high Ampere. not sure about the specs, but over here, normal house-wiring is 16A. so the sockets, plugs, switches etc. will handle a bit more than that. it would not handle high watt 12V devices. so it s not the best solution.

i ve got a small desktop LEd lamp which runs on batteries or could be plugged to USB, that s nice.

are there any laptops which can be charged via USB? in know about tablets, that can... but laptops?

Not really as far as I know, save for a few Intel Atom tablets with keyboards magnetically attached, but the new USB PD standard is supposed to be designed to allow charging of laptops with USB and sharing power with devices. For instance, any USB device with a power source or battery can charge another USB device that has the same or lower power profile. Their documentation goes over the proposed methods of determining what does what under different circumstances.

It probably would be better to use a DC-DC power supply designed to charge a laptop from a cigarette lighter/power port. There are also a number of PC monitors out there using ~19V power bricks which could also be powered by one of those laptop car chargers. Combining that with a M3-ATX Pico PSU from mini-box or similar power supply can create a nice off grid solution for a desktop computer.

I picked up one of those M3-ATX PSU's many years ago and have it running the computer I am typing on now. I dug it up more than a year ago and found that for lower power computers, using it with a power brick used less energy than standard ATX power supplies. The computer I was testing went from ~40 watts at idle to just under 30 watts. 10 watts may not seem like much, but a 25% reducing in power usage is enormous for an off grid situation. I got a newer motherboard with a built in CPU that draws around 12 watts idle and 22 watts max. It isn't fantastic, but it does everything I need. These numbers are via a power brick plugged in to a Kill-A-Watt meter, so I am certain it would be more efficient directly connected to batteries. I don't have any good test equipment to measure power draw, but I will try to give it a shot in the coming months.

This again is where the USB PD would shine. I could rig up the 12VDC USB power to this computer and be well below the 100 watt limit. Not that I need it for myself, but it could introduce new markets for green building and power. There is a race to the bottom of power consumption between ARM and[ x86 based processors. Right now on the desktop the Intel x86 processors still have the best performance per watt per dollar spent from what I have seen for desktop solutions. However the lines are beginning to blur and it is creating a lot of new opportunities for powering devices with renewable energy. The new Raspberry Pi 3 certainly looks nice for quite a few tasks such as lightweight desktop or HTPC and takes USB power. Not to mention the dozen of developer boards that have come out since the success of the Raspberry Pi.

daniel, that s interesting stuff. i imagine, one could build a "desktop" computer into a very small space in a tiny house.

thank you for putting your effort here...

have blessed and nice easter holidays