Im happy to explain pastermil. So first off let’s talk power.
Electrical Power Systems
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.
AC vs DC Appliances
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 easy to transmit long distance however its very high voltage so only very power hungry devices like kitchen appliances and washing machines and AC compressors use it directly. It’s why american homes have a seperate 240v circuit for kitchen and basement.
Offgrid electrical systems with batteries tend are DC powered by nature. The difference is technical but the way the power flows through the system is different. Direct current moves in a straight path while alternating current moves back and forth.
Most consumer devices in your home dont actually use wall outlet AC power directly, it uses converted stepped down DC power. Desktop computer power supplies, Laptops, monitors, vaporizers, led lights, DVD players, audio speakers, your phone. everything that can powered by usb and batteries. Everything that has barrel plug inputs and power bricks plugging into it.
If you look closely on the power bricks plugged into the appliance 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.
Device vs Voltage Examples
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.
Energy Conversion Efficency Losses
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 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
Convert the DC power of the batteries to AC through an inverter. 15% efficency loss.
Then convert that power right back down into DC with the power brick plugged in. 15% efficency loss.
The inverter and power brick are both parasitic draws. They eat a bit of power just sitting there even if nothing is being powered. Lets add 5% total system efficency loss each.
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?
What DC-to-DC Converters Are
Thats where dc to dc converters come in. They still introduce efficency loss but way way less only 10% total.
Traditionally you would hope your device had a 3rd party travel adapter for car batteries and use car plugs. If you were SOL you has to wire up boost converters to raise up voltage and add resistors in series to lower it. You ever try to wire and solder your own circuts before? Its a tedious experience. Imagine doing that for each device voltage.
A USBC-pd 100w charger that plugs into a cigarette port or is built into a power bank 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.
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.
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.
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.
One of DCs main issues is transmission distance. Its hard to say for your case without details but its a good possibility. 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.
Im happy to explain pastermil. So first off let’s talk power.
Electrical Power Systems
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.
AC vs DC Appliances
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 easy to transmit long distance however its very high voltage so only very power hungry devices like kitchen appliances and washing machines and AC compressors use it directly. It’s why american homes have a seperate 240v circuit for kitchen and basement.
Offgrid electrical systems with batteries tend are DC powered by nature. The difference is technical but the way the power flows through the system is different. Direct current moves in a straight path while alternating current moves back and forth.
Most consumer devices in your home dont actually use wall outlet AC power directly, it uses converted stepped down DC power. Desktop computer power supplies, Laptops, monitors, vaporizers, led lights, DVD players, audio speakers, your phone. everything that can powered by usb and batteries. Everything that has barrel plug inputs and power bricks plugging into it.
If you look closely on the power bricks plugged into the appliance 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.
Device vs Voltage Examples
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.
Energy Conversion Efficency Losses
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 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?
What DC-to-DC Converters Are
Thats where dc to dc converters come in. They still introduce efficency loss but way way less only 10% total.
Traditionally you would hope your device had a 3rd party travel adapter for car batteries and use car plugs. If you were SOL you has to wire up boost converters to raise up voltage and add resistors in series to lower it. You ever try to wire and solder your own circuts before? Its a tedious experience. Imagine doing that for each device voltage.
A USBC-pd 100w charger that plugs into a cigarette port or is built into a power bank 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.
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.
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.
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.
One of DCs main issues is transmission distance. Its hard to say for your case without details but its a good possibility. 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.