7 ms·

Searching for USB Power Supplies That Won't Explode

78 points by szczys 11y ago

tibbon 11y ago
From what I've experienced, most power supplies are just awful and don't hold up at all to their specs, especially current in excess of 500mA. I've been working with LEDs recently (APA102s), and I attempted just doing some testing with 4 meters (60 LEDs/m) and a cheap old 5VDC laptop power supply that in theory was rated for 5A+. Didn't work so well. Overheating, not providing enough current to keep the LEDs acting stable, power on spike, etc... To solve my problem, I've purchased two 5V 90A Meanwell power supplies, and those seem to work pretty well. But needless to say, I cannot imagine cheap/small power adapters working well at all. At my day job, we have some hardware that requires 800mA at peak to run. Even many 1A USB supplies we've found to offer nowhere near that current capacity. And if they do, they frequently fail after a while.
- andmarios 10y ago
  With a quick look, APA102 LEDs draw 0.04-0.2A. Even at minimum intensity, we have 4m × 60 LED × 0.04A = 9.6A for the best case scenario.
- Gibbon1 10y ago
  > we have some hardware that requires 800mA at peak to run. Even many 1A USB supplies I've been doing this for 30 years now. My rule is. Power supplies? Derate by 50% or you will be sorry. That power IC that says it's good for 1.2A? Yeah read that as 600ma. Capacitors are the same way, rated for 16 volts? Try 10 volts. If you look at capacitors specs you'll often see MTBF at rated voltage and temperature of 2000 hours which is three months.
  - gh02t 10y ago
    Usually I see a big voltage sag when you get near the rated voltage on most wall wart type supplies. I try and stick to 50% or maybe 75% if I think it's quality.
- digi_owl 10y ago
  > At my day job, we have some hardware that requires 800mA at peak to run. Even many 1A USB supplies we've found to offer nowhere near that current capacity. And if they do, they frequently fail after a while. What you could be running into there is a charger OEM that thinks Apple way is the proper way. Thing i that Apple uses a couple of resistors on the data pins to give slightly different V between them this indicates to an Apple device that they can go 1A or higher. But the USB spec says to basically short the data pins. Depending on the device OEM you may have the device think it is dealing with a normal computer port rather than charging port when encountering the Apple setup, and dropping back down to .5A.
darkclarity 10y ago
I think the best power supplies are those commissioned by big manufacturers to go with their hardware. The HP Touchpad's power plug being a good example. These brands don't want a poorly designed adapter killing their products.
- manyxcxi 10y ago
  I was going to say something similar. I often use USB power supplies that came from old phones/laptops for my various little robot/gizmo projects. I do this with the (naive) assumption that If I'm Apple/Dell/Samsung/etc. I don't want to taint my products because of bad power supplies. Other than using my non-pro knowledge and tools to roughly test voltage stability, sustained amperage, and output voltages on some of the power supplies, I don't have any hard evidence that this is true- but if I'm choosing between an Apple USB power supply or a no-name power supply from Amazon for a project, I'm taking the Apple one because I can assume it's a minimum level of quality that's good enough for my use. I've got a couple of iPad USB power adapters that I guard pretty closely because the other USB power supplies I have that say they're good for at least an amp or two are from no-name suppliers.
- NoGravitas 10y ago
  My (Asus) Nexus 7 charger died, and none of the cheap replacement chargers I found would charge my tablet. Bought an HP Touchpad power plug off of eBay based on an XDA Developers recommendation. Worked perfectly for years.
mrob 10y ago
Sometimes even a well designed and assembled power supply can be dangerous because of defective components. Big Clive on Youtube does many teardowns of cheap electronics, and here's one of a USB power supply that's dangerous because of internal damage to the transformer: https://www.youtube.com/watch?v=3Hdn0MuCK_0 https://www.youtube.com/watch?v=3Hdn0MuCK_0 Because this is an intermittent fault it's possible that non-destructive testing would not find it.
- Obi_Juan_Kenobi 10y ago
  That's not a random failure, though. The quality control for the transformer manufacturing was inadequate. This wasn't some difficult to anticipate error, either; maintaining the integrity of the winding insulation is basically the most important thing to monitor. The machines were either poorly designed or improperly operated. Sourcing higher quality components would prevent such issues. I'll concede that nothing can be perfect, but this type of error is preventable. It starts to cost quite a bit when you move from 0.1% error to 0.01%, though.
  - tsomctl 10y ago
    It's not just quality control on the part of the transformer manufacturer. It was a cheap design. They could've completely isolated the two transformer windings, either with heavy tape, or wound them on two separate bobbins. That way, if the enamel on the wire wears off, the two sides are still completely isolated. I still agree with your conclusion, though.
  - aembleton 10y ago
    They might not have been built by machines. Here's a video of those transformers being made: https://www.youtube.com/watch?v=HEJn74Z3wHk https://www.youtube.com/watch?v=HEJn74Z3wHk
synaesthesisx 10y ago
There's a difference between active and passive protection systems - similar to certain Lithium-ion batteries. A lot of the cheaper manufacturers skimp out on a lot of such components (hence why you hear of e-cigs blowing up, etc).
LeoPanthera 10y ago
I trust Anker's chargers more than anyone elses. (No association with them, just a happy customer.) In general, chargers from big brands (Apple, Amazon, Samsung, even Ikea) are fine because they don't want to risk damage to their brand if one were to burn down a house or something. If your charger has a brand you've never heard of, beware!
- TazeTSchnitzel 10y ago
  Also, don't trust the name on the case. Know the provenance. There are plenty of fake chargers out there that look on the outside identical, down to the tiniest details, to Apple chargers, for example.
- swah 10y ago
  Me too - my Anker car charger delivers 1800 mAh as measured by an Android app called Ampere - I can charge my phone only during commute and use it for 24 hours. A cable I have from them is also high quality. OTOH some Ebay cables might drop it down to 500 mAh. It was a shock to me because for years I exclusively bought Ebay chargers and cables (around 1/5 of the price of Anker) thinking they would work as specified (or not at all)...
  - digi_owl 10y ago
    Different gauge on the power wires give different results during charging. The original .5A of USB worked well with 28 AWG, but you need to go with 24 AWG to get 1A or more out of a charger. Sadly very few cables list this kind of info. And even when you have the proper cable, you can run into the problem that the charger manufacturer thought the Apple way was the proper way. Thing is that Apple has some very odd resistor setup on the data pins to indicate max A out of their chargers, while the USB charger spec basically says to short the data pins so that the device can sense it. Try to charge a non-Apple device in an Apple type charger and you can get anything from full to .5A, depending on how clever the device engineers were...
  - arantius 10y ago
    FYI: "mAh" or milli-amp-hours is a unit of capacity, in this case it makes no sense. Perhaps you mean just "mA", a unit of current, which does make sense in context?
eumoria 10y ago
This is obvious to the point of not reiterating but don't ever plug your stuff into cheap/unknown chargers. I've seen the AC jump across to the low power DC side MANY times and it insta-destroys anything designed to just take the +5vdc. I work in the event industry and we supply recharging cabinets for corporate events. We use Anker.
mrbill 10y ago
After reading Ken Shirriff's review a few years ago, I bought a bunch of Touchpad chargers off eBay (before the clones started appearing) and use them for tons of stuff. http://www.righto.com/2012/10/a-dozen-usb-chargers-in-lab-apple-is.html http://www.righto.com/2012/10/a-dozen-usb-chargers-in-lab-ap... Otherwise I stick with Anker/Aukey; am a huge fan of the 6-port "charger bricks" and have used one next to my bed (phone, two tablets, a couple of USB-powered devices like a sleep monitor) for 3-4 years now.
nikanj 10y ago
I've been searching for a good-quality usb hub. After a few years of intense competition, there are basically two options on the market: cheap chinese crap, and cheap chinese crap in an expensive designer enclosure.
- paulmd 10y ago
  It's not like any of it's made in America, so... I have one of these and it's been fine so far. http://www.amazon.com/EasyAcc-Bus-Powered-Self-Powered-Ultrabooks-Microsoft/dp/B00ID270ZU http://www.amazon.com/EasyAcc-Bus-Powered-Self-Powered-Ultra... To reiterate everyone else, Anker is great. I've had good results with TronSmart too. And the Amazon Basics lineup is universally reliable. They have all sorts of chargers/hubs/cables at reasonable prices.
  - voltagex_ 10y ago
    If anyone can shed some light on the supply chain for these I'd be interested - I've seen Anker, Aukey and Tronsmart 5 or 6 port chargers that look identical (performance has been almost identical too, luckily). I can't buy Anker or Aukey in Australia (easily / for a reasonable price) but I can get Tronsmart through Geekbuying.
- illumin8 10y ago
  I have a couple Anker USB 3 hubs (one is a 9 port and one a 7 port) and they have not had any issues.
- dawnerd 10y ago
  I've had really good luck with this one from Amazon http://www.amazon.com/AmazonBasics-Port-USB-3-0-Hub/dp/B00GGYU8TC/ http://www.amazon.com/AmazonBasics-Port-USB-3-0-Hub/dp/B00GG... It's fairly inexpensive (there's smaller versions too), is powered, and backed by Amazon if there's an issue.
binman 10y ago
Here are some good analytical reviews of USB power hardware, including safety: http://www.lygte-info.dk/info/indexUSB%20UK.html http://www.lygte-info.dk/info/indexUSB%20UK.html In general I buy Anker stuff - decent pricing and solid stability/quality/safety.
dublinben 10y ago
I've been very satisfied with my charger from ChoeTech. I figure that if something is Qualcomm Quick Charge Certified, then it is probably adequate to charge my devices.
- seanp2k2 10y ago
  For inexpensive USB power, Anker has been my go-to. They also do the Qualcomm quick charge with many of their products. Related, I liked their stuff so much, and was so impressed when ripping apart one to use for lots of 5V amps, that I bought their LED desk lamp (Lumos A2) which I've been very satisfied with. They also have the E1 out now, which is more powerful as lumens go. Edit: tear down of the charger I like by Anker (thanks binman): http://lygte-info.dk/review/USBpower%20Anker%2040W%205-port%2071AN7105%20UK.html http://lygte-info.dk/review/USBpower%20Anker%2040W%205-port%...
fpgaminer 10y ago
Makes me wonder if DC wiring will ever catch on in newer homes. We don't have much need for AC anymore. The only places in a home where one needs AC is in the kitchen for large appliances, and garage/laundry room. And really that's just because of the motors. I'm not sure if those could be converted to DC motors and what powerloss that might entail. But the point stands; you could totally get away with building a new home where you drop AC to the kitchen and garage, and then 12VDC+5VDC everywhere else (12V on the wires, put a regulator to drop to 5V in the outlet for USB-C ports). The power-loss of DC in a home won't be that large. The end result is that the AC to DC transformer will be centralized to one location, where you can spend more money up front to get higher reliability, cleaner power, better safety, and better efficiency. Plus, if you have solar, you can avoid AC to DC conversation altogether, saving on a good chunk of powerloss there. The caveat, of course, is that lots of devices don't natively support DC input. Phones, tablets, and modern USB-C laptops are fine. Lighting is easy; just do permanent LED installations. The LEDs will last a very long time since they won't have regulators in them. Desktops are an issue. I believe the only desktops that support DC input are HTPC builds, using those micro PSUs. Perhaps there's an HTPC PSU that's got enough beef to power a normal desktop? You'd also have to find monitors that accept DC input, which do exist but that will narrow your market significantly. Rob Rhinehart is an early adopter (see: http://robrhinehart.com/?p=1331 http://robrhinehart.com/?p=1331) of this type of home. Sounds crazy, but it seemed like a glimpse at a hopeful future, at least everything outside of the kitchen.
- mmagin 10y ago
  Well, uh, AC vs DC and 100-250 volts versus 5-48 volts are two completely different dimensions to the problem here. For example, there has been some standardization of high voltage DC power distribution for datacenters, seeing as that could simplify providing battery backup, etc. But back to the residential case: As soon as you go to lower voltage power distribution, unless you spend a lot more on copper (larger conductors), you're really hurting as far as power distribution losses: your load uses 10 times as many amps running on 12 volts DC as it did on 120 volts RMS AC. Thus your loss due to the resistance of the wire is 100 times what it was, given the same wiring. (i.e. the same series resistance -- your loss is P = V * I = I^2 * R) And no, you don't suddenly get much greater efficiency in the power supply of the device - a lot of off-line power supply designs today are already 90% efficient, and even if you provide 12 volts (or 12 and 5) to the plug, there's going to be a lot of things you want to do in the device that does not satisfy, and if you want exactly 12, you're going to need some kind of DC-DC converter with regulation, because you cannot predict how the 12 volt supplied at the wall will go down due to other load at any given point in time -- so just like a laptop has various DC-DC converters from the 18 volts supplied by its power brick to the various internal circuits (Vcore logic, 1.8 volt logic, 3.3 volt, 5 volt USB, backlight circuits, etc) most devices will still have that. They might not require as much safety isolation, but you're not going to get them to be magically far more efficient than what we have today.
mmagin 10y ago
I generally avoid anything that doesn't have legitimate safety certifications: UL, ETL, TUV, etc. ("CE" as printed on random imported crap seems to mean nothing in particular.) Also, you can usually count on actual, non-counterfeit chargers from well-respected phone and tablet vendors being just fine. I've never thrown out an old USB charger from an iphone, samsung, motorola, asus, just put them in a box for possible later use :)
- sbierwagen 10y ago
  "CE" as printed on random imported crap seems to mean nothing in particular. http://www.icomuk.co.uk/News_Article/3794/17103/ http://www.icomuk.co.uk/News_Article/3794/17103/ https://en.wikipedia.org/wiki/CE_marking#China_Export https://en.wikipedia.org/wiki/CE_marking#China_Export

78 points by szczys 11y ago

From what I've experienced, most power supplies are just awful and don't hold up at all to their specs, especially current in excess of 500mA. I've been working with LEDs recently (APA102s), and I attempted just doing some testing with 4 meters (60 LEDs/m) and a cheap old 5VDC laptop power supply that in theory was rated for 5A+. Didn't work so well. Overheating, not providing enough current to keep the LEDs acting stable, power on spike, etc... To solve my problem, I've purchased two 5V 90A Meanwell power supplies, and those seem to work pretty well. But needless to say, I cannot imagine cheap/small power adapters working well at all. At my day job, we have some hardware that requires 800mA at peak to run. Even many 1A USB supplies we've found to offer nowhere near that current capacity. And if they do, they frequently fail after a while.

andmarios 10y ago
With a quick look, APA102 LEDs draw 0.04-0.2A. Even at minimum intensity, we have 4m × 60 LED × 0.04A = 9.6A for the best case scenario.
Gibbon1 10y ago
> we have some hardware that requires 800mA at peak to run. Even many 1A USB supplies I've been doing this for 30 years now. My rule is. Power supplies? Derate by 50% or you will be sorry. That power IC that says it's good for 1.2A? Yeah read that as 600ma. Capacitors are the same way, rated for 16 volts? Try 10 volts. If you look at capacitors specs you'll often see MTBF at rated voltage and temperature of 2000 hours which is three months.
- gh02t 10y ago
  Usually I see a big voltage sag when you get near the rated voltage on most wall wart type supplies. I try and stick to 50% or maybe 75% if I think it's quality.
digi_owl 10y ago
> At my day job, we have some hardware that requires 800mA at peak to run. Even many 1A USB supplies we've found to offer nowhere near that current capacity. And if they do, they frequently fail after a while. What you could be running into there is a charger OEM that thinks Apple way is the proper way. Thing i that Apple uses a couple of resistors on the data pins to give slightly different V between them this indicates to an Apple device that they can go 1A or higher. But the USB spec says to basically short the data pins. Depending on the device OEM you may have the device think it is dealing with a normal computer port rather than charging port when encountering the Apple setup, and dropping back down to .5A.

darkclarity 10y ago

I think the best power supplies are those commissioned by big manufacturers to go with their hardware. The HP Touchpad's power plug being a good example. These brands don't want a poorly designed adapter killing their products.

manyxcxi 10y ago
I was going to say something similar. I often use USB power supplies that came from old phones/laptops for my various little robot/gizmo projects. I do this with the (naive) assumption that If I'm Apple/Dell/Samsung/etc. I don't want to taint my products because of bad power supplies. Other than using my non-pro knowledge and tools to roughly test voltage stability, sustained amperage, and output voltages on some of the power supplies, I don't have any hard evidence that this is true- but if I'm choosing between an Apple USB power supply or a no-name power supply from Amazon for a project, I'm taking the Apple one because I can assume it's a minimum level of quality that's good enough for my use. I've got a couple of iPad USB power adapters that I guard pretty closely because the other USB power supplies I have that say they're good for at least an amp or two are from no-name suppliers.
NoGravitas 10y ago
My (Asus) Nexus 7 charger died, and none of the cheap replacement chargers I found would charge my tablet. Bought an HP Touchpad power plug off of eBay based on an XDA Developers recommendation. Worked perfectly for years.

mrob 10y ago

Sometimes even a well designed and assembled power supply can be dangerous because of defective components. Big Clive on Youtube does many teardowns of cheap electronics, and here's one of a USB power supply that's dangerous because of internal damage to the transformer: https://www.youtube.com/watch?v=3Hdn0MuCK_0 https://www.youtube.com/watch?v=3Hdn0MuCK_0 Because this is an intermittent fault it's possible that non-destructive testing would not find it.

Obi_Juan_Kenobi 10y ago
That's not a random failure, though. The quality control for the transformer manufacturing was inadequate. This wasn't some difficult to anticipate error, either; maintaining the integrity of the winding insulation is basically the most important thing to monitor. The machines were either poorly designed or improperly operated. Sourcing higher quality components would prevent such issues. I'll concede that nothing can be perfect, but this type of error is preventable. It starts to cost quite a bit when you move from 0.1% error to 0.01%, though.
- tsomctl 10y ago
  It's not just quality control on the part of the transformer manufacturer. It was a cheap design. They could've completely isolated the two transformer windings, either with heavy tape, or wound them on two separate bobbins. That way, if the enamel on the wire wears off, the two sides are still completely isolated. I still agree with your conclusion, though.
- aembleton 10y ago
  They might not have been built by machines. Here's a video of those transformers being made: https://www.youtube.com/watch?v=HEJn74Z3wHk https://www.youtube.com/watch?v=HEJn74Z3wHk

synaesthesisx 10y ago

There's a difference between active and passive protection systems - similar to certain Lithium-ion batteries. A lot of the cheaper manufacturers skimp out on a lot of such components (hence why you hear of e-cigs blowing up, etc).

LeoPanthera 10y ago

I trust Anker's chargers more than anyone elses. (No association with them, just a happy customer.) In general, chargers from big brands (Apple, Amazon, Samsung, even Ikea) are fine because they don't want to risk damage to their brand if one were to burn down a house or something. If your charger has a brand you've never heard of, beware!

TazeTSchnitzel 10y ago
Also, don't trust the name on the case. Know the provenance. There are plenty of fake chargers out there that look on the outside identical, down to the tiniest details, to Apple chargers, for example.
swah 10y ago
Me too - my Anker car charger delivers 1800 mAh as measured by an Android app called Ampere - I can charge my phone only during commute and use it for 24 hours. A cable I have from them is also high quality. OTOH some Ebay cables might drop it down to 500 mAh. It was a shock to me because for years I exclusively bought Ebay chargers and cables (around 1/5 of the price of Anker) thinking they would work as specified (or not at all)...
- digi_owl 10y ago
  Different gauge on the power wires give different results during charging. The original .5A of USB worked well with 28 AWG, but you need to go with 24 AWG to get 1A or more out of a charger. Sadly very few cables list this kind of info. And even when you have the proper cable, you can run into the problem that the charger manufacturer thought the Apple way was the proper way. Thing is that Apple has some very odd resistor setup on the data pins to indicate max A out of their chargers, while the USB charger spec basically says to short the data pins so that the device can sense it. Try to charge a non-Apple device in an Apple type charger and you can get anything from full to .5A, depending on how clever the device engineers were...
- arantius 10y ago
  FYI: "mAh" or milli-amp-hours is a unit of capacity, in this case it makes no sense. Perhaps you mean just "mA", a unit of current, which does make sense in context?

eumoria 10y ago

This is obvious to the point of not reiterating but don't ever plug your stuff into cheap/unknown chargers. I've seen the AC jump across to the low power DC side MANY times and it insta-destroys anything designed to just take the +5vdc. I work in the event industry and we supply recharging cabinets for corporate events. We use Anker.

mrbill 10y ago

After reading Ken Shirriff's review a few years ago, I bought a bunch of Touchpad chargers off eBay (before the clones started appearing) and use them for tons of stuff. http://www.righto.com/2012/10/a-dozen-usb-chargers-in-lab-apple-is.html http://www.righto.com/2012/10/a-dozen-usb-chargers-in-lab-ap... Otherwise I stick with Anker/Aukey; am a huge fan of the 6-port "charger bricks" and have used one next to my bed (phone, two tablets, a couple of USB-powered devices like a sleep monitor) for 3-4 years now.

nikanj 10y ago

I've been searching for a good-quality usb hub. After a few years of intense competition, there are basically two options on the market: cheap chinese crap, and cheap chinese crap in an expensive designer enclosure.

paulmd 10y ago
It's not like any of it's made in America, so... I have one of these and it's been fine so far. http://www.amazon.com/EasyAcc-Bus-Powered-Self-Powered-Ultrabooks-Microsoft/dp/B00ID270ZU http://www.amazon.com/EasyAcc-Bus-Powered-Self-Powered-Ultra... To reiterate everyone else, Anker is great. I've had good results with TronSmart too. And the Amazon Basics lineup is universally reliable. They have all sorts of chargers/hubs/cables at reasonable prices.
- voltagex_ 10y ago
  If anyone can shed some light on the supply chain for these I'd be interested - I've seen Anker, Aukey and Tronsmart 5 or 6 port chargers that look identical (performance has been almost identical too, luckily). I can't buy Anker or Aukey in Australia (easily / for a reasonable price) but I can get Tronsmart through Geekbuying.
illumin8 10y ago
I have a couple Anker USB 3 hubs (one is a 9 port and one a 7 port) and they have not had any issues.
dawnerd 10y ago
I've had really good luck with this one from Amazon http://www.amazon.com/AmazonBasics-Port-USB-3-0-Hub/dp/B00GGYU8TC/ http://www.amazon.com/AmazonBasics-Port-USB-3-0-Hub/dp/B00GG... It's fairly inexpensive (there's smaller versions too), is powered, and backed by Amazon if there's an issue.

binman 10y ago

Here are some good analytical reviews of USB power hardware, including safety: http://www.lygte-info.dk/info/indexUSB%20UK.html http://www.lygte-info.dk/info/indexUSB%20UK.html In general I buy Anker stuff - decent pricing and solid stability/quality/safety.

dublinben 10y ago

I've been very satisfied with my charger from ChoeTech. I figure that if something is Qualcomm Quick Charge Certified, then it is probably adequate to charge my devices.

seanp2k2 10y ago
For inexpensive USB power, Anker has been my go-to. They also do the Qualcomm quick charge with many of their products. Related, I liked their stuff so much, and was so impressed when ripping apart one to use for lots of 5V amps, that I bought their LED desk lamp (Lumos A2) which I've been very satisfied with. They also have the E1 out now, which is more powerful as lumens go. Edit: tear down of the charger I like by Anker (thanks binman): http://lygte-info.dk/review/USBpower%20Anker%2040W%205-port%2071AN7105%20UK.html http://lygte-info.dk/review/USBpower%20Anker%2040W%205-port%...

fpgaminer 10y ago

Makes me wonder if DC wiring will ever catch on in newer homes. We don't have much need for AC anymore. The only places in a home where one needs AC is in the kitchen for large appliances, and garage/laundry room. And really that's just because of the motors. I'm not sure if those could be converted to DC motors and what powerloss that might entail. But the point stands; you could totally get away with building a new home where you drop AC to the kitchen and garage, and then 12VDC+5VDC everywhere else (12V on the wires, put a regulator to drop to 5V in the outlet for USB-C ports). The power-loss of DC in a home won't be that large. The end result is that the AC to DC transformer will be centralized to one location, where you can spend more money up front to get higher reliability, cleaner power, better safety, and better efficiency. Plus, if you have solar, you can avoid AC to DC conversation altogether, saving on a good chunk of powerloss there. The caveat, of course, is that lots of devices don't natively support DC input. Phones, tablets, and modern USB-C laptops are fine. Lighting is easy; just do permanent LED installations. The LEDs will last a very long time since they won't have regulators in them. Desktops are an issue. I believe the only desktops that support DC input are HTPC builds, using those micro PSUs. Perhaps there's an HTPC PSU that's got enough beef to power a normal desktop? You'd also have to find monitors that accept DC input, which do exist but that will narrow your market significantly. Rob Rhinehart is an early adopter (see: http://robrhinehart.com/?p=1331 http://robrhinehart.com/?p=1331) of this type of home. Sounds crazy, but it seemed like a glimpse at a hopeful future, at least everything outside of the kitchen.

mmagin 10y ago
Well, uh, AC vs DC and 100-250 volts versus 5-48 volts are two completely different dimensions to the problem here. For example, there has been some standardization of high voltage DC power distribution for datacenters, seeing as that could simplify providing battery backup, etc. But back to the residential case: As soon as you go to lower voltage power distribution, unless you spend a lot more on copper (larger conductors), you're really hurting as far as power distribution losses: your load uses 10 times as many amps running on 12 volts DC as it did on 120 volts RMS AC. Thus your loss due to the resistance of the wire is 100 times what it was, given the same wiring. (i.e. the same series resistance -- your loss is P = V * I = I^2 * R) And no, you don't suddenly get much greater efficiency in the power supply of the device - a lot of off-line power supply designs today are already 90% efficient, and even if you provide 12 volts (or 12 and 5) to the plug, there's going to be a lot of things you want to do in the device that does not satisfy, and if you want exactly 12, you're going to need some kind of DC-DC converter with regulation, because you cannot predict how the 12 volt supplied at the wall will go down due to other load at any given point in time -- so just like a laptop has various DC-DC converters from the 18 volts supplied by its power brick to the various internal circuits (Vcore logic, 1.8 volt logic, 3.3 volt, 5 volt USB, backlight circuits, etc) most devices will still have that. They might not require as much safety isolation, but you're not going to get them to be magically far more efficient than what we have today.

mmagin 10y ago

I generally avoid anything that doesn't have legitimate safety certifications: UL, ETL, TUV, etc. ("CE" as printed on random imported crap seems to mean nothing in particular.) Also, you can usually count on actual, non-counterfeit chargers from well-respected phone and tablet vendors being just fine. I've never thrown out an old USB charger from an iphone, samsung, motorola, asus, just put them in a box for possible later use :)

sbierwagen 10y ago
"CE" as printed on random imported crap seems to mean nothing in particular. http://www.icomuk.co.uk/News_Article/3794/17103/ http://www.icomuk.co.uk/News_Article/3794/17103/ https://en.wikipedia.org/wiki/CE_marking#China_Export https://en.wikipedia.org/wiki/CE_marking#China_Export