tetris11How much of a game changer was USB-C for you, compared to other cables?
SmokeyDopeUsbc-pd is an absolute game changer as an off grid person. The facg a 100w charger can act as a dc to dc converter with up to five output voltages, at up to 100 watts is crazy. And that the protocol automatically detects and communicates the proper voltage is very convinent. The problem is that usbc-pd 100w chargers are expensive and you need to know what you are doing if you want to diy power appliances with it.
pastermilI’m curious as to what exactly you do with it as an off-grid person, and what you mean by DC-to-DC converter.
Im happy to explain pastermil. So first off let’s talk power. Most off-grid electrical systems have a few major components. A device that generates electrical energy, a battery that stores excess electrical energy for later, and a power distribution interface which allows for connecting appliances to the batteries in a safe standardized way.
My particular electric system has a 200w solar panel for power generation, two 20ah lifepo4 batteries for capacitance, and the charge controller acts as a very basic interface with two usba slots and a car cigarette port.
Now let’s talk about AC and DC appliances. Theres essentially two kinds of electrical power people deal with. The one most people are familiar with is AC power it comes to your home from power plants through power lines and transformer boxes. Its very high voltage so only high power devices like kitchen appliances and washing machines and AC compressors use it directly. It’s why american homes have a special circuit for 240v.
Besides that, most consumer devices dont actually use AC power, it uses DC power. Desktop computer power supplies, Laptops, monitors, vaporizers, led lights, DVD players, audio speakers, everything that can powered by usb and batteries. Everything that has barrel plug inputs and power bricks.
If you look closely on the power bricks that plug into your wall, you’ll see that it has an input and output voltage rating. The input tends to be 120vac here in america 240v over the pond, and the output tends to be either 5v, 9v, 12v, 15v or 20v DC usually up to 5 amps.
Laptops and computer monitors tend to be 20v, fast charging smart phones and the Nintendo switch docked are 15v, very bright home LED lights can be bought that are powered at 12v directly, the ps2 could be powered with 9v, and most usb devices charge at standard 5v. Would you like to guess which voltage profiles the USBC-PD protocol is capable of? Its all of them.
Now let’s discuss energy efficiency. Converting from AC to DC eats up some of your power. So does converting from DC to AC. And its not small losses either, each time you convert its about a 10-15% loss in efficency.
This loss through conversion doesn’t matter when you pay cents on a kilowatt and have unlimited power at the tap. It adds up very quickly when you have a limited power supply.
Let’s say I want to power a laptop on my offgrid DC system, and I only know how to power it with the AC cable that it came with. I would need to
Add these up and you get 30-40% of your power eaten up needlessly double converting the power. Wouldnt it be really nice if we could convert the battery DC voltage directly to the appliance DC voltage without those power hungry inverters and transformers?
Thats where dc to dc converters come in. They still introduce efficency loss but way way less only 10% total. A USBC-pd 100w car charger that plugs into a cigarette port can convert a batteries 12vDC into 5v, 9v, 12v 15v, and 20v dynamically depending on the device.
Do you know how magical that is? How much trouble that saves when it comes to mcguyvering a DC appliance that only came with AC cable to supply proper power directly? All I need is a 10$ cable to manually select the voltage needed and some barrel plug adapter bits to fit into the appliance.
Is DC why my 12V water pump doesn’t run but the LED bulbs on the same circuit are fine? The pump is by the creek and I’m thinking it can’t pull enough amps over the length of the run. Working on that today.
If you have a volt meter and know how to use it check the voltage at the start of the run and compare it to the end of the run and see how much the voltage has dropped. If your trying to push 12v over 20-30ft I would say theres a good chance of it being too little voltage over too far a length. Wire diameter is also a factor if its very small gauge wiring.
No voltage drop, but it’s an easy 80’, maybe 100, maybe even a little more. Hard to say as it cuts through the woods.
Picked up an old Fluke at the store, I’ll try an figure out how to read amps.
Did you measure voltage drop across the pump while it’s trying to start up? The voltage will only drop when there’s current being drawn. So with the pump off you woukd see full supplt volts even on a highly resistive line. You could try lugging a battery down to the pump, and jump it to get it started, then remove the battery jumpers but keep the pump running on your main run, then measure the volts across the pump.
I appreciate that you’re really thorough, both with that explaination as well as the implementation in the first place.
I guess I’ve never give it much thought. I mean, I’m familiar with electricity, but I’m paying dirt cheap for it.
One more question: How do you do your lighting? Most light fixtures I know are using e27 bulbs, which are AC powered. I know the LED panels requires driver circuits between them and the main, theoretically they probably could live off your DC straight-up, but they’re generally a pain to work with.
Thanks. Lighting has been an ongoing puzzle I’m figuring out. I originally went with rechargeable Luci light it was really nice warm bright lighting but expensive and failed within a season. Currently I’m using a cheap 5v plastic led light bulb that plugs into regular usba slot. Its enough to see what you are doing comfortably. But really the average person whos used to house bulbs including me wants the luxury of bright lighting. For now I’ve been firing up the AC inverter to run a nice lamp. However I have been considering making my own 12v light fixture with 12v e26 bulbs that plugs into either car cig plug or usbc-pd.
In this picture is marked all the parts of an LED circuit that convert AC Into DC. It takes up about 40% of the board. Its much easier to power LEDs directly.
entropicdriftHey entropicdrift good question. Those kinds of lanterns are expensive and complicated electronics with a definitive life expectancy. The lantern you linked is over 20$ for a single unit. It uses a non replaceable rechargeable lithium battery built inside it that will only last about 500 charge cycles give or take before degrading, if you are lucky and one of the other cheap electrical components doesn’t fry first.
In the long term I deem its more cost efficient to create a simple light fixture with easily and cheaply replaceable bulbs. A pack of 4 cost less than that lantern.
Its also a simple matter to convert any lamp fixture into one that can interface with my power system. Cut off the AC plug and replace it with a male cigarette plug. The trick is knowing thst you have to buy the right kinds of bulbs.
So when the 12v led bulbs do eventually burn out its a cheap single 5$ bulb that and a minute to replace it.
Apotential benefit if I choose to power it with usbc-pd instead is variable dimmable lighting based on voltage level if the bulb is 12-24v.
Thank you! Very enlightening (heh)
Hi! You seem knowledgeable about this stuff, so if you can answer a question. I have an older Jackery power station that has a single USB-C PD port. I need more when camping and I have been plugging a AC USB-C charger into one of the AC ports on the power station. From what you wrote that make me think that is not an efficient way due to the conversion from DC to AC to DC. Would I be better off using the DC “Car Charger” port or maybe a USB-C hub of some sort?
Hey there panicnow! I would be happy to help give some input. It is better to avoid firing up the AC inverter whenever possible. If you have a car travel adapter for your devices that plug into the jackeries cigarette plug port that would be better. If you absolutely need more usbc-pd ports for your devices, there is a way to do that given your jackary has one or two of those circular barrel plug outputs that output 12v. Most powersttions should have one or two of them.
If you have one of those barrel plug inputs youre in luck. Go on amazon and buy one of these to turn those jacks into car cigarette plug inputs.
Then get a really nice usbc-pd car charger. I don’t actually have one but I like anker and trust their 100w pd charger would be high quality. You can go cheaper if you only need 65w or lower.
Thanks so much! I was kind of on that line after I read your earlier comment, but thought I would just ask. My jackery doesn’t have barrel plug outputs—just inputs. But it does have a 12V, 10A cigarette plug port. I’ll get an anker car charger like you suggested and use that.
Blaze (he/him)Great explanation, FYU I just posted this to [email protected]
now someone needs to make USB-C jack to barrel plug “tips” with the PD chip built in so I can substitute USB-C for wall wart transformers.
Hey aubeynarf think you are talking about something like this.
Its a special usbc-pd to 5.5x2.5 barrel jack with manually selectable voltage. You just plug it into a pd charger and select the voltage of the device. The rest is finding a barrel plug to barrel plug adapter that plugs into your device. Hope this helps.
I want that whole arrangement to be in a tip with a USB-C receptacle and a fixed voltage and barrel size so it’s barely bigger than my thumbnail and can be used with standard usb-c cables.
So I can get a “9V-5.5x2.5-Pos” to convert my casio keyboard to usbc, without all that other stuff hanging off and extra, unnecessary pieces
If your device happens to be 18-20v you can get a usbc-pd laptop connector with a dc barrel jack output. It has the USBC-PD chip built into it to tell the charger to output 20v and you can probably hunt down barrel adapter bits.
The other voltages are tough theres not really a consumer market for 15v or 9v specific usbcPD to barrel things.