
A dozen USB chargers in the lab: Apple is very good, but not quite the best - pmarin
http://www.arcfn.com/2012/10/a-dozen-usb-chargers-in-lab-apple-is.html
======
GuiA
" Since the designers of the Apple charger went to a great deal of effort to
build a high quality charger, I conclude they must not consider voltage sag
worth worrying about. Or, more interestingly, maybe they built this sag as a
feature for some reason. In any case, the chargers lose points on this."

I'm not versed in the arcane arts of EE— could anyone give me a basic
definition of voltage sag? And would there be any reason to build it as a
feature in a charger?

~~~
kens
Hi, the author here. I'm using voltage sag to describe how the voltage drops
as the load increases. (This has nothing to do with the presence of a battery
or not.) Chargers normally are designed to output a constant voltage until the
charger hits maximum power. But with the iPhone charger, the voltage is 5.2
volts if there's no load, and steadily drops to 4.6 volts as the load
increases. If a device is expecting 5 volts, this could cause problems. Also,
charging times could increase since the voltage is lower.

Generally, if the voltage drops under load like this, it's a sign of a poorly
designed charger that doesn't regulate well. But since Apple's charger appears
otherwise well-designed, it's a bit of a puzzle. One possibility is that maybe
the exact voltage input to the iPhone doesn't matter, and the designers
knowing this didn't care about the voltage sag. Another possibility is for
some unknown reason they deliberately designed the charger this way.

~~~
sliverstorm
It's almost always a balance between cost of manufacture and performance. I
would bet money it was not designed that way as a feature.

The interesting points to remember here are:

\- USB specifies 5V, not the iPhone

\- Voltage drop across the iPhone's internal regulators and charging circuits
are probably less than 0.5V

\- Most cell phone LiIon batteries are 3.7V

So, presumably they made a charger that allows droop to 4.6V because this is a
voltage still capable of charging the battery, yet also allows a less
expensive charger design.

~~~
zokier
> USB specifies 5V, not the iPhone

Afaik USB specs are 5V+-10%, ie 4.5V-5.5V. So the iphone charger is well
within the spec and all conforming devices should be able to handle that.

------
nicpottier
Too bad the Amazon Kindle charger isn't in the mix, it is my favorite just
because it is so tiny and relatively high output. Would have liked to see same
analysis for it.

~~~
Lagged2Death
I've got 3 USB chargers in the house, including a Kindle charger, and none of
them inter-operate at all. Ridiculous.

~~~
nicholassmith
Out of curiousity whereabouts are you based? I'm in the UK and have about 5
different USB chargers, and they all play nice with each other.

~~~
Lagged2Death
I live in the US.

The chargers _look_ like they'll work together. For example, the Kindle
charger will make my pocket camera light up its charging light, but after a
minute or so, it goes out, as if the charge has completed. In fact, though,
the battery is still dead. The other combinations of cell phone / camera /
Kindle chargers are similar.

------
commandar
I bought up a half dozen Touchpad chargers when they were being cleared out
for $5 a piece. I did it mainly because they were the cheapest 2A adapters
that work with anything I'd come across, but it's good to know they're
efficient and well-built as well.

~~~
Tsts
Is it dangerous to use a high output power charger, like the HP TouchPad one,
with a low consumption device, like a phone?

~~~
dhbanes
No, the current rating is the maximum output of the charger. It's up to
connected device to draw as much current as it needs, rather than the charger
pushing the current into the device.

~~~
zokier
Afaik it's not that clear cut. If some kind of fault occurs in the device
causing it to draw more current than designed then the lower power charger
could be safer assuming it has some kind of current limiter or fuse. Ie high
power charger would happily give faulty device more current possibly causing
more damage (heating up, exploding batteries etc), while a low power charger
could prevent that by tripping a fuse or limiting current.

Of course I'm not sure if this is applicable to USB chargers which all are
relatively low power.

------
acgourley
The lesson here is that if you don't want to pay for an official apple
charger, _do not buy a counterfeit one_ just buy any name brand one with the
right wattage rating.

~~~
kmfrk
And even with Apple chargers you risk using a charger with the wrong wattage
(iPad charger vs. iPhone/iPod IIRC).

~~~
Moto7451
But there will be no damage which is more important. My iPad simply slow
charges (1A) on my old iPhone & my newer/current Samsung & LG 1A phone
charger. Meanwhile my iPad charger works on all my devices - retired iPod
Mini, my old iPhone 3G (now iAlarm Clock), Samsung Admire, LG Motion 4G, iPod
Touch 7G. In the latter case, charging isn't any faster of course since the
devices will only pull 500mA (Admire) or 1A.

The only chargers that I have that won't charge my all of my modern iDevices
are old ones meant for iPods (500mA, no signal on the data pins) and my old
Belkin iPhone car charger doesn't work with my iPad (Probably only 500mA w/
signal for iPhones. I'd have to check).

Another interesting tidbit: It appears that my car's Pioneer DEH 9400 head
unit (aftermarket of course) seems to inform my devices that it can supply 1A
of power through its two USB ports. This is the first time I've seen that
outside of dedicated chargers and Macs (I assume of course that some PCs do
this as well but I haven't seen one yet).

~~~
RShiki
> This is the first time I've seen that outside of dedicated chargers and Macs
> (I assume of course that some PCs do this as well but I haven't seen one
> yet).

My Asus motherboard can do that with the right software/driver installed and
it seems that all products made by Asus these days support this. It's an
optional install you can find in the Asus support website for your devices.

~~~
kmfrk
Ai Charger, specifically:

<http://event.asus.com/mb/2010/ai_charger/>

<http://asus-ai-charger.en.uptodown.com/>

I had to uninstall it, when I upgraded from Windows 7 to 8, though.

------
rhplus
This link just wouldn't have been quite as clickable: _A dozen USB chargers in
the lab: HP is the best_.

~~~
gnu8
Its an appeal to the Apple sycophants who troll this web site: "oh no who
dares best my beloved Apple?!? I'd better click!"

~~~
redcircle
Would you like a higher quality site? Belittling comments such as this, to a
group of the users here, will not get us there.

------
macleodan
I have looked at some cheap car USB power supplies.

Griffin: [http://mm0hai.net/blog/2012/09/30/Griffin-USB-Car-
Charger.ht...](http://mm0hai.net/blog/2012/09/30/Griffin-USB-Car-Charger.html)

Unbranded, common on ebay. [http://mm0hai.net/blog/2012/08/01/Message-to-an-
ebay-seller....](http://mm0hai.net/blog/2012/08/01/Message-to-an-ebay-
seller.html)

They were both awful. I would be interested to know about a known good one.

------
kens
A lot of people have suggested additional chargers I should examine. To narrow
it down, I've created a poll on the article page (upper left). If there's
sufficient interest I'll take a look at your favorite charger, so cast your
vote.

------
mhb
Would be nice to know how the adafruit charger does:

<http://adafruit.com/products/501>

~~~
rhizome
I bought two for ~$3 apiece at Fry's a few months ago. One is OK, the other
was and is DOA. The one that mostly works sometimes requires jiggling in the
jack to make contact, but generally they are a garbage, F-, would not buy
again product.

~~~
ladyada
Hi Rhizome, adafruit does not distribute the specific USB charger we carry at
Frys - sorry to hear you had a bad experience with them but it was certainly
not the same one from the adafruit shop the parent poster was referring to!

~~~
rhizome
This appears to be what I purchased, and it looks exactly the same:

<http://www.frys.com/product/6740515>

~~~
ladyada
I assure you that just because two adapters look the same do not have any
relation to the insides. (After all, counterfeit Apple adapters look the same
as genuine ones, but you wouldn't think they are the same on the inside after
reading this article.) The black plug casing is a common molding style used by
many factories - but its the electronics inside that count :) The best way to
know if they are identical is to look for the UL certificate number, those are
unique to each design.

We have a photo of our label here
<http://www.adafruit.com/images/large/ID501label_LRG.jpg>

~~~
rhizome
I can assure you that as a run-of-the-mill customer, I will likely never check
a UL code. I don't know if you get your casings from the same place, putting
your own electronics inside, but I feel that if you want to trade on your
identity as a purveyor of quality products you're going to have to look at
least a little different from bad products. To borrow and twist a line from
Seinfeld, "Adjacent to trash, is trash."

<http://www.youtube.com/watch?v=KKC5jjFkfgo>

I did make the mistake, though, so sorry about that.

~~~
sliverstorm
ladyada does not manufacture that charger; the website offers it, along with
other general-purpose knickknacks, to compliment the main offerings- DIY
electronics kits. This last bit is significant- ladyada's run-of-the-mill
customer is not going to be your standard Joe looking for a charger for his
cell phone.

------
mseebach
It's off-topic, but I've been trying to figure it out for a while: I have a
two-port "Gear4" USB charger with swappable plugs, so it's great for
travelling. However, my new work BlackBerry won't accept a charge from it,
complaining about it being too low powered - however, the Gear4 charger says
it's 2A, the BB charger is 750mA.

Does anyone know what's the deal?

~~~
philh
On a similar note: I have a second generation iPod nano. Years ago I took a
spare cable for it and cut the data wires, hoping to be able to plug it into a
computer to charge while still being able to play music. (I saw this tip
somewhere online.)

It worked with my brother's iPod classic (maybe 5th gen?), but not my nano;
later I saw something on Adafruit about how the iPhone needed specific
voltages on the data pins to charge, and I figured that was what was going on.

But recently, I got a battery pack, which can output to microUSB, iPod, or
some other things. It works with my iPod, the same one I had years ago. But
the cables it came with have swappable ends, I think 2.something mm jacks. At
any rate they only have two points of connection. Here's what it looks like:
<http://i.imgur.com/8TliS.jpeg>

So, how does this work? As far as I can tell, this should be exactly the same
situation as a standard USB-iPod charger with its data cables cut, but it's
not behaving the same.

It's possible I'm getting some details wrong, but can anyone shed some light
on this?

~~~
joenathan
The data pins may be shorted or bridged on your battery packs' cable.

------
kalleboo
I got a nice charger from Buffalo (respected Japanese brand) that does a max
of 4A (=can charge 2 iPads at once) and has 4 USB ports: 2 with the Apple
power negotiation standard, and 2 with the Everyone Else/Android power
negotiation standard.

It'd be nice to see an even broader test

------
rhizome
I'm pretty sure there is a guaranteed-success Kickstarter for a $10-20 clean-
charging plug in this story.

~~~
wib
Yes. I've never given to a Kickstarter campaign but would totally contribute
to this. Proprietary chargers feel like such a ripoff at ~$30-$50, but clearly
the $5 generics are a bad buy, so what you're suggesting is a real
opportunity.

------
polyfractal
Very interesting review, I enjoyed the dissection and review of what most
people don't even think about (wall chargers).

On a non-technical note, Apple chargers should lose simply because of how
goddamned large they are. They basically eat two spots on a power strip and
are easily knocked out of wall sockets because of their weight.

~~~
kalleboo
One thing that always annoys me when Apple products take over the world is how
they are limited to American constraints. Sony Ericsson made a brilliant
charger that plugged into the wall and you could just stand your phone onto.
Apple would never think of that since the American plug standard is too weak
to carry the same weight a Schuko can. And now everyone has to copy Apple
instead of innovating...

~~~
micampe
Not everyone.

<http://www.bluelounge.com/products/minidock/>

[http://www.amazon.com/Digital-Lifestyle-Outfitters-
DLA49002-...](http://www.amazon.com/Digital-Lifestyle-Outfitters-
DLA49002-17/dp/B002VPDM2K)

<http://store.griffintechnology.com/iphone/powerblock-2011>

------
afterburner
Good to know Monoprice makes a good product.

~~~
vostrocity
Other than the fact that it's butt ugly and comes with an unwieldy loose
cable.

~~~
afterburner
That's ok, there's plenty of other Monoprice chargers.

------
adrr
I have a fake IPad charger, it barely charges my IPhone and can't charge the
IPad at all. It was labelled as an Apple charger when I bought it for $10 and
had good reviews.

------
yooy123
USB chargers? Try this one, I wish I could afford it.

[http://kdyworks.com/index.php?option=com_content&view=ar...](http://kdyworks.com/index.php?option=com_content&view=article&id=46&Itemid=59)

~~~
yooy123
This one is also nice

<http://www.ubergizmo.com/2009/07/cambrionix-49-port-usb-hub/>

------
nodrama
what about noise? Audio noise. If it works, this is the next feature I'm
interested in. For example, I have an HP laptop, and the charger is noisy.

