Better 12 volt cable standard for solar systems?

Beholder

Senior Member
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1,006
Now that people get solar panels for prepping and saving energy, should lamps, laptops and other devices have a new cable standard between USB-C and high voltage to get rid of up and down volting loss? Even though my laptop charges with a 12 volt cable and solar power regulators often provide 12 volts, I can't plug my laptop directly into a solar power system because the power regulator may not fulfill oscilation margins if the controller is too slow at high input voltage. Using the laptop's adapter would require volting up from 12 to 230 volts, only to volt back down to 12 volts with the warranty approved adapter, wasting lots of power on electromagnetism and heat for a voltage that fills no purpose for locally produced energy with low cable resistance.
 
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MODAT7

Member
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478
Yeah, it's a mess. I've been thinking about building some custom power adaptors that are much more efficient, but my health problems have been really slowing me down. If you measure your laptop power brick, it probably puts out 19v like most others. In full sunlight, most 12v solar panels will put out something close to this. Under load, they will be less. My old netbook is low power enough that it could probably run straight off a small solar panel at noon that I have, but it uses a tiny custom power connector that I don't have. Most laptops/netbooks don't have an internal 12v rail anymore (unlike desktops), so could probably run on a lower voltage without power management kicking in. Just don't expect to charge the battery at any real rate. In the old days, I'd sometimes run one of my laptops off a 12v lead acid brick battery down to 10.5v (plugged into the power barrel connector). It would trigger low power warnings, but it would still work. If you think about the typical 3 cell lithium battery pack, this would be about the level it would trigger a shutdown. In most modern processors and chips, they run 1.2-3.3v, so can take lower input voltages so long as the main power supply doesn't decide to turn off.

Oddly USB-C includes a higher voltage standard mostly intended for battery charging. I haven't done any USB-C microcontroller projects, so I can't say much else on it.

Along the same step up/down complaints, I've been thinking about my own custom UPS for years that would be far more efficient than store bought. It would still step up to 120v for the computer power supply, and that would lose another 20% efficiency stepping back down... which got me thinking about just dumping the computer power supply totally and generating my own 12v, 5v, and 3.3v rails directly.

For off grid, 12v LED car lamps could be used off of a solar battery system. It wouldn't be too hard to modify a 120v/220v desk lamp to work with that system. Maybe use some high output flashlight bulbs instead of something for a car. That might be a little more efficient and generate less waste heat. Most commercial LED lights are medium efficiency because of cost. More industrial suppliers like Digi-Key and Mouser offer high efficienty LEDs that are more expensive but use far less current and could be used for off grid. They need soldering iron and hot air wand experience, though... which isn't too hard to learn for simple stuff.
 

Beholder

Senior Member
Messages
1,006
Yeah, it's a mess. I've been thinking about building some custom power adaptors that are much more efficient, but my health problems have been really slowing me down. If you measure your laptop power brick, it probably puts out 19v like most others. In full sunlight, most 12v solar panels will put out something close to this. Under load, they will be less. My old netbook is low power enough that it could probably run straight off a small solar panel at noon that I have, but it uses a tiny custom power connector that I don't have. Most laptops/netbooks don't have an internal 12v rail anymore (unlike desktops), so could probably run on a lower voltage without power management kicking in. Just don't expect to charge the battery at any real rate. In the old days, I'd sometimes run one of my laptops off a 12v lead acid brick battery down to 10.5v (plugged into the power barrel connector). It would trigger low power warnings, but it would still work. If you think about the typical 3 cell lithium battery pack, this would be about the level it would trigger a shutdown. In most modern processors and chips, they run 1.2-3.3v, so can take lower input voltages so long as the main power supply doesn't decide to turn off.

Oddly USB-C includes a higher voltage standard mostly intended for battery charging. I haven't done any USB-C microcontroller projects, so I can't say much else on it.

Along the same step up/down complaints, I've been thinking about my own custom UPS for years that would be far more efficient than store bought. It would still step up to 120v for the computer power supply, and that would lose another 20% efficiency stepping back down... which got me thinking about just dumping the computer power supply totally and generating my own 12v, 5v, and 3.3v rails directly.

For off grid, 12v LED car lamps could be used off of a solar battery system. It wouldn't be too hard to modify a 120v/220v desk lamp to work with that system. Maybe use some high output flashlight bulbs instead of something for a car. That might be a little more efficient and generate less waste heat. Most commercial LED lights are medium efficiency because of cost. More industrial suppliers like Digi-Key and Mouser offer high efficienty LEDs that are more expensive but use far less current and could be used for off grid. They need soldering iron and hot air wand experience, though... which isn't too hard to learn for simple stuff.
The adapter for my HTPC sais 19 volts, so maybe a separate buck regulator from 24 volts would work with enough margin and keep out noise from other drains. Multiple processors can't sit on the same regulator anyway.
 

MODAT7

Member
Messages
478
The adapter for my HTPC sais 19 volts, so maybe a separate buck regulator from 24 volts would work with enough margin and keep out noise from other drains. Multiple processors can't sit on the same regulator anyway.
You can have lots of processors on the same regulator. It just needs to have enough current to be stable. If a processor (or digital chip in general) produces a lot of rail noise, then it will need isolation and/or a lot of capacitance to filter it (probably throw in some inductors). Main PC CPU's often have a large bank of capacitors around them. The other problem mentioned is ground noise / ground bounce. That's more of a layout design issue, and depending on the chip frequency, can get into magic. They usually need a good star topology that they don't get. Things like audio ADC/DACs are obviously sensistive to noise, so they usually have extra separation... or at least they "should".

When doing audio, for example, most USB ports are heavily criticized for being noisy, when it's mostly a ground noise issue from the rest of the computer. That's not the easiest thing to clean up.
 

Beholder

Senior Member
Messages
1,006
Around half of my devices use 55x21mm DC cables with the black marking, so with a rare male to male DC5521 cable directly from power station to monitor, I can probably save the 4 watts of idle power that the transformer drew just from being plugged in, plus the ~20% lost on conversion. This would bring down the cost of streaming movies with Chromecast from 13 watts to somewhere near 8 watts. The portable DVD player will still be the most energy efficient entertainment at 5 watts. I will probably look for the DC5521 cable standard when buying new products and get those cables in bulk from China to double how long I can go without the grid on my battery.
 

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