We've had a lot of talk about USB standards here lately!

For our family's next trip, I'd like to leave the portable power strip behind - along with as many USB chargers as possible - and just bring a hub and cables. Is this going to be possible?

I have an Anker hub with 9 ports, but two of those are advertised as charging ports. I've charged some light devices off the other ports, but I guess I don't understand enough about USB power to know what's going on in there. Is there any hub/device on the market that charge, say 5 phones at once? Is this basically what I'm looking for? Even if it is, I'd love to understand this issue more...

Yeah, gadgets like the one you linked are the state of the art for charging many things from a single outlet. Be careful to read the Amazon reviews, since not everything that's advertised as >1A (@5W) is going to work correctly with all the Apple and/or Android devices.

That one seems to claim it'll work equally with Android and Apple devices. Perhaps there are some smarts in there to detect what's plugged in?

I could be wrong about this, but, if I recall correctly, it's the other way round. The phone is what has the smarts.

I seem to recall that there is some handshaking going on, where the phone/tablet queries the power supply to see if it can deliver a higher-amperage charge signal. I know we've discussed that elsewhere here on the BBS. Apples, for example, have some smarts where they try to detect if they are hooked up to a cheap Chinese charger, and if so, will only try to draw the minimum from that charger, just to be safe. If they detect that they are connected to an actual Apple charger, it will detect the type of charger (large or small) and then draw the appropriate amperage depending on what it finds out.

What I don't know is how exactly the device goes about querying the power supply. I seem to recall that's the details that we discussed here elsewhere on the BBS a while ago.

So your third party charger thingy will, at a minimum, work correctly for slow-charging your devices no matter what. The only question is whether your devices will be convinced that the charger can deliver the higher charge rate, and then take advantage of that for quicker charging.

Confusion regarding USB and charging is widespread, commonly misunderstood even among those that otherwise feel comfortable with 'tech'.

I have yet to see a multi port USB charger that even claims to be able to deliver maximum charging power to all outlets at the same time, let alone a charger that actually does so. As in the example linked above, the maximum power output of the charger is less than the maximum per port output, multiplied by the number of ports.

2.4 amps per port times 5 volts (all commonly found USB is 5 volts, excluding the very recent USB-C and special cases) equals 12 watts per port. 12 * 6 ports is 72 watts, which is significantly more than the '50 watt' product description.

When you plug in a recent model iPad or an iPhone 6/6+ the device will sense the claimed maximum power output of the charger (via signals on the USB port data pins), then attempt to draw the full 10 or 12 watts that the device can absorb. If the charger output voltage stays stable at 5.00 volts or slightly above then the device will draw the maximum allowed power and recharge in the quickest possible time frame.

If the charger cannot maintain the necessary precise 5.00 volts when the device ratchets up the requested charging current then the device will back down the power demand until the charger can again provide a stable charging voltage. You will not see any indication on the Apple device regarding which charging rate is happening, as long as the rate is at or above the minimum.

When the minimum power is not available, (for example) a full sized iPad needs more than 2.5 watts to simply run with the LCD display lit up. If the iPad is plugged into a USB power source that can only deliver the basic 2.5 watts then the iPad will show the 'Not Charging' message where the lightning bolt icon would normally appear (top right corner). When the iPad is sleeping (LCD screen is dark) it will indeed be charging, just very slowly.

How this particular charger will cope with multiple devices that in aggregate demand more than the rated 50 watts, I cannot predict. How your connected devices respond when the charger begins to dial back the available power per per port will depend on the particular devices, and the order in which they are connected. The first three or four devices I would expect to receive full charging power, beyond that would depend on the device mix. And their individual states of charge.

* The 10 Amps spec is related to the 50 watts maximum for the charger overall.
5 volts times 10 amps equals 50 watts.

Excellent explanation.

True, but I don't think they're exactly misleading people. They're not saying you'll be charging six iPads at full power (though as you say, I don't know what would happen then either), they're just giving you the maximum potential output, and 10 amps is more than I'll need.

Here's what I need to charge on a typical family vacation, in which a device like this would typically be found plugged near a nightstand or dresser:

- my wife's iPhone 6
- my Nexus 6
- Moto 360 stand
- 2 bluetooth headphone sets
- Nexus 7 tablet

I don't think my nexus 7 charges at 2.4 amps, so this should put me under the 10 amp total for that device. In that case, I think I'll go ahead and get that thing.

But thanks for some clarification of USB charging.

A couple of mentions of querying the charger here.

Is it that complex or still simply detected by various resistances on the data lines to +5V/GND/each other. That's certainly how older products worked.

Monitoring the voltage and throttling back is a neat way to do it.

It all started off somewhat simply, with the USB port data pins either shorted together or not, then Apple added certain fixed DC voltages on each pin (using resistor voltage ladders) to indicate which power level a charger was rated for. I think Apple has defined three or four discreet charger wattage levels using this method.
http://empegbbs.com/ubbthreads.php/topics/349650#Post349650

Of course the non-Apple and China USB chargers created different ways to indicate charger power capabilities, and with some different power level increments.

We are now at the point where the better USB chargers have a special chip inside which pretends to emulate the 'simple' power signals of each charger type, until the chip finds a pin/signal combo that the 'smart' device at the other end likes and starts drawing lots of current.

So the two ends do a little a signaling 'dance' where each end tries to determine what the other end wants or is capable of. As you can imagine, it all gets more complicated as additional layers of newer specs and USB charging power levels are introduced.

USB-C seems likely to add a whole extra level of 'interesting' to the process.

That is crazy. It seems so simple to somebody as simple as I am, plug it in and it charges.

This board (and EE folks in general) are amazing. No way could I ever understand that stuff.

Often the things that seem 'simple' to the end user involve significant internal complexity, masked by the software or hardware implementation of the electronics. The dark side is that quite often the process behind creating the solution is wrought from compromise and mis-steps. Sometimes it all works out nicely, sometimes it becomes a mess internally, with sub-optimal options going forwards.

In my view USB includes aspects from across the spectrum, the most visible of which may be the multitude of USB connector sizes and variations, especially on the 'B' end.

I did not mention in the prior description of USB charging that there is also a 'smart' negotiation protocol that is used when the charging device is a computer or similar. The host and end devices 'discuss' what is possible and work out what amount of power the device will take from the host. Apple uses this method when you plug an iPhone or iPad directly into a Mac, for example.

There is, of course, also a non-Apple protocol that does similar with Windows USB ports.

While it won't help you Matt, some laptop come with a USB port (see image) that will stay powered even when the laptop is powered off, enabling devices to charge from it - and for some one less think to haul. Note: I had to enable this feature in the BIOS on my laptop.

Look for a port with the lightening bolt

Sorry for the resurrection of this thread, but I couldn't find a newer one, and this didn't quite seem to fit the usb-c cable discussions...

Does anyone have any ideas on a good wall-wart with 4+ usb ports to charge various devices? Ideally something relatively compact, 110-240V, and usb-c compliant.

thanks,

-jk

If you want four or more ports, you're looking at something bigger than a wall-wart. I've got my eye on this new Anker product: http://www.amazon.com/Anker-Premium-Charger-PowerPort-Delivery/dp/B01D8C6ULO/

Four "normal" USB-A ports and one USB-C power port that can shove out 29W for charging a MacBook or other such gadget. That's a pretty cool solution to the "taking the family on vacation and must charge all the things with minimum travel weight" problem.

See also, USB outlets:
http://www.amazon.com/Leviton-USB4P-W-4-2-Amp-4-Port-Charger/dp/B00FANAWY6/

And power strips with USB ports in them. Here's one with USB-C:
http://www.amazon.com/JOTO-Protector-Charger-Charging-Station/dp/B01AT281AY/

Is USB-C a requirement or a future proofing nice-to-have?

USB-C as in capable of some higher rate of charge than 12 watts?
USB-C has many grades of spec ...

thanks! That first one looks good.

-jk

USB-C is definitely a future thing... Nothing I have today needs it, but I hate buying almost obsolete stuff, especially when I'm replacing failed obsolete stuff.

-jk

There is a presumption that first generation USB-C chargers will be long term compatible and optimal for future variations of USB-C and whatever standards oddness lies next in wait.

There was/is already a kerfuffle regarding the Qualcomm Quick Charge 3.0 variant and 'proper' USB-C compatibility.

Somehow I get this feeling that there are more USB-C issues yet to surface, and not just from Qualcomm.

Even today, what does a full specification USB-C charger look like? Does it provide up to 100 watts? 15watts, 18 watts, 36 watts? At what voltages? Per port?

USB power Delivery spec revision 1, or rev 2?

This USB-C charger from Google offers up to 60 watts but has a captive cable. The Apple 29 watt version not only works with the new MacBook but also fast charges the 12" iPad Pro.

Right now it seems rare to find a multiport USB-C charger that can provide more than 5 volts and 15 watts. Eventually that should change, I expect.

That was the stated purpose for starting this thread! I ended up with the device I linked in my initial post. I've taken it on several trips already, and it's been super convenient. It's so nice to keep all the wall warts there they are (usually tucked behind night stands), and streamline my go bag. I do still have a bunch of cables I need to bring, but this device and a half dozen USB cables takes far less space than those cables and a half dozen wall warts. I was also able to ditch a power strip I used to carry, and I'm able to charge more devices at once than I used to.

I used to just bring a few chargers. One would charge my phone at night, and when I left a hotel room for the day I'd plug that charger into my tablet to have it ready for the evening. Now I can charge every device I own.

I'm very interested in using USB C to charge my XPS 13. So far, though, I haven't been able to charge it. The charger that came with my Nexus 5X can't do it, but that doesn't surprise me. I just don't know which of the chargers out there are capable, though, and that's yet another annoyance of USB C.

I have also purchased several of the Choetech six port chargers, very happy with them so far, also recommended to friends.

No compatibility issues, fast 12 watt (2.4amp) charging on the multiple Apple devices that support that charge rate. Android and other stuff charges just fine.

No issues with heat. Compact enough device size.

The power cord jack is a standard figure-8 two wire cord, so very easy to buy or scrounge a replacement cord when on the road. Euro cord and US cords both pack easily in luggage.

I have been using a DROK USB 3.0 charge monitor device , quite handy to confirm actual charging rates.

Not to mention it's pretty darn inexpensive.

I'd forgotten that I've actually replaced most of my nightstand chargers with one of those things.

The most authoritative source on all of this seems to be Benson Leung (Google engineer and one-man Underwriters Laboratories). https://plus.google.com/u/0/+BensonLeung

With regard to all the different power delivery profiles, he nicely summarized:

For the Quick Charge kerfuffle, he wrote that the USB-C spec prohibits Qualcomm's QuickCharge, flat out. (https://plus.google.com/+BensonLeung/posts/cEvVQLXhyRX)

(Always fun to stir things up...)

So how does the consumer know whether their USB-C stuff complies with the new rules or the slightly older rules?



The watt rating shortcut presumes that all devices, cables and power sources are using the same rules. Which Benson has done an excellent job of showing is not always the case.



12 volts is optional ... For whom? If the USB-C device requires it, can the power source deny the request?

For multi-port USB-C chargers there is the potential additional complication when the aggregate power available across all ports combined is less than the maximum power available from each port. Now that multiple port voltages and current capacities are in play it is important that the charger deliver the appropriate power on each port, even if the devices on the other ports are also highly demanding.



Common among USB 2.x multiport chargers is to not allow full power on all ports at the same time. Even the rather nice Choetech six port 50 watt charger cannot deliver a full 12 watts from all six ports at the same time.

I have done no reading at all on what it means to have a multi-port USB-C hub (not just a charger) in terms of power management. Not to mention routing DisplayPort style video through the hub or back charging the laptop through the hub. Don't even know if those things are possible.