Microblog Memes

I am off-grid for much of the time so I rely on an entirely DC to DC system. 200 watts of solar panels power up my batteries which supply 12V at a capacity of about 400 watt hours. So for many appliances like laptops and speakers and computer screens which use DC power it makes sense to try to convert the voltages directly though other means than the typical AC to DC power plug supplies that you usually use in homes. Doing this I can cut down total power consumption for each device down by about half which is really important for conserving power on a limited energy supply.

In a theoretical scenario you could totally run a seperate voltage line for DC energy through a house, though this has several complications. The main drawback of DC energy is that the lower the voltage the more resistance losses you get running power through a foot of cable. So the cable losses would become signifigant after running 200 feet of cable probably less even. You could bump up the voltage to 48VDC for longer stretches of wire and to power high end RV appliances but now were loosing some of the safety that comes from a lower voltage DC system. Im not familiar with commercial solar installations in homes but I think its easier and more economical to eat inverter losses and use the batteries to supply AC power using preexisting wiring. If you were building a offgrid home its a design thing to consider, reducing and centralizing wiring and appliances.

They have solar + batteries, so they have to convert the sun into DC, hopefully directly supply that DC to their batteries, then convert that DC to AC power, then convert that AC power back to DC. Converting AC to DC or vise versa is a reasonably lossy process, so not doing double the conversion is even better.

Also some less than ideal setups convert solar directly to AC, so in order to charge your batteries you have to convert it back to DC.

Thanks, glad to have inspired you! The other person who replied is spot on. I have an entirely DC system so my main advantage comes from cutting out pointless double-conversion from dc to ac back to dc again. Powering on an DC to AC inverter is a parasitic draw that consumes enough power to eat through a good amount of battery capacity if left on by itself. Then using that AC inverter just to power another inverter to step back to DC introduces even more losses and parasitic load. So, its worth my time to try figuring out ways to directly power devices by directly converting DC to DC voltages and cut those needless loads out greatly boosting total efficiency.

USBC-PD technology is an incredibly useful innovation for direct variable dc to dc voltage supply. Specifically a 100 watt usbc-pd charger can supply 5v,9v, 15v, 20v at up to 5 amps (5Ax20V=100 watts). A car cigarette plug can supply 12V at 10A or 120 watts of power. Together they can directly power a great many household DC appliances off of batteries powering a DC to DC inverter.

For some examples:

A 24" lcd computer monitor at full brightness consumed 50Wh through AC inverter. It was brought down to 25Wh running through DC inverter. On half brightness it consumed 15Wh and 10Wh at minimum brightness.

A thinkpad laptop full brightness was 25wh idle -50wh full load, then brought down to 12-20wh.

My nintendo switch game console docked into the lcd screen consumed about 15-20Wh with inverter, brought down to 10Wh.

Desktop dry herb vaporizer (Arizer Extreme Q): 80Wh heating up, 30-50wh idle brought down to 50Wh heating up 15-25Wh idle.

Electric blankets. During the cold months using my electical energy to help keep warm is very important to me. But I cannot keep a regular house electric blanket on for more than an hour or two. I could not keep a car plug blanket on overnight at 80wh. I could keep on a USB powered blanket on overnight at 10-15Wh. And you know what suprised me most? It was damn warm, when I figured out the right way to sleep with it. Have to sleep on it as a matress warmer and layer some heavy blankets on top and let it warm up for an hour or two. But it works and works well. The USB blanket doubles as wearable poncho too which is nice. I wish a USBC-PD one existed with variable wattages.

So as you can see each time I macguyver a way to directly power these devices the total power usage is cut by almost half per device. To someone else who can afford an array of solar panels and a massive bank of batteries they can get away with not caring about saving 20Wh here or 15Wh there. I have a very modest system of 200watts solar feeding into ~400Wh battery capacity total so these savings mean the difference between my batteries being dead overnight and having lots of spare juice left over to brew a cup of coffee with those AC inverters when I wake up.

Of all these devices listed, the LCD monitor is one that has a noticable parasitic load even when the screen is off it consumes a noticable amount of power at idle. The way I would deal with most instances of parasitic draw like this is to find a product throws a physical switch to manually cut contacts with the DC-DC inverter when not being used. In this case a car plug extention cable with a knife switch built in would work great.