Develop Bugs

Quick Charging USB Adapter... Any thoughts?

I am considering buying this usb charging adapter cable to help speed up my charging rate at work where I don't have an AC adapter and my work computer's usb ports are conveniently placed. From what I have read, normal usb charging maxes out at 500ma, but can be increased if your usb port has more juice if you short the data wires, which will tell the phone to grab more power because it thinks it is plugged into an AC adapter.
I have found this adapter http://www.dealextreme.com/p/usb-data-charging-extension-cable-for-samsung-p1000-black-91141
it is meant for a galaxy tab, but From what I see is that it has a switch that either allows data / slow charge or allows quick charging. I have purchased a few of these already because I'm assuming it will still work with my galaxy s2.
I'll let everyone know how it goes, but does anybody see a problem with this or think I'm going to fry my phone for any reason?
Thanks.

very interesting, heck it's only $3 bucks, might as well just buy it and find out
yes, charging via USB port sucks, it's too slow at 500 mAh
if that does the magic trick, by shorting it and making it believe it's an AC then it'll be nice, and it can pull around 1000 mAh off the USB port (depending on your computer mainboard)

Id be curious to see if this actually works but i see no fault in trying it

cbutters said:
I am considering buying this usb charging adapter cable to help speed up my charging rate at work where I don't have an AC adapter and my work computer's usb ports are conveniently placed. From what I have read, normal usb charging maxes out at 500ma, but can be increased if your usb port has more juice if you short the data wires, which will tell the phone to grab more power because it thinks it is plugged into an AC adapter.
I have found this adapter http://www.dealextreme.com/p/usb-data-charging-extension-cable-for-samsung-p1000-black-91141
it is meant for a galaxy tab, but From what I see is that it has a switch that either allows data / slow charge or allows quick charging. I have purchased a few of these already because I'm assuming it will still work with my galaxy s2.
I'll let everyone know how it goes, but does anybody see a problem with this or think I'm going to fry my phone for any reason?
Thanks.
Click to expand...
Click to collapse
Only the Galaxy Tablets have this limitation (they cannot be charged at all via computer usb only via their "special" wall adapter) so the adapter won't do anything for a phone. The adapter works on the tablet because what the adapter is doing is shorting 2 pins on the USB cable to fool the TABLET into thinking it is on the AC adapter "specially made" for it.
As long as you plug the phone it into a self-powered usb port (ie: a hub with a power brick) you will get max current the phone allows. The adapter will make no difference on the phone because the phone CAN charge off the PC port while the tablet cannot. It won't hurt the phone but it won't help it either.

MisterEdF said:
The adapter will make no difference on the phone because the phone CAN charge off the PC port while the tablet cannot. It won't hurt the phone but it won't help it either.
Click to expand...
Click to collapse
Thanks for the info on the galaxy tab, however I disagree with you in your opinion that an adapter that shorts the data wires will not help the phone to charge quicker.
It seems either the devices or android system itself limits charging to 500ma so it does not damage the computer, the phone itself knows that it is connected via usb, and will state "Charging: USB Plugged"
If you let the phone think it is connected to an AC adapter, it will allow the battery to accept whatever amperage you throw at it, and you will see that the system states "Charging: AC Plugged"
Obviously there are two modes of charging going on here.
See this thread:
see here:
http://forum.xda-developers.com/showthread.php?t=844284

Has anyone tried this yet?

I have found that using the Galaxy Tab chargers works the same way. They have a 2amp output vs the .5 amps that most blackberry chargers and USB use... It shortens the charge time significantly.
TMO SGS2, Darkside 3v8, Kernel Venom 3#5, UVLC8

Charger considerations
Hi,
I need advise for the following:
Charger A (Li-polymer battery) output : 5V, 1A
Charger B (Li-polymer battery) output : 5V, 500mA
Device input: 5V, 750mAH (Li-ion / Li-polymer)
When using Charger A, some people comment that it will limit the current of 750mAH for the device and the device's battery should be fine since both the charger and device are at 5V. However, some people comment that this will shorten the battery life of the device since it will perform a 'quick charge' using 1A.
When using Charger B, some people comment that the device will draw more current than it can deliver and causes it to heat up and reduces the charger's life. However, some people comment that Charger B will extend the battery life of the device since it performs a 'slow charge'.
I also read that USB pins on the charger denotes if the charger is a PC or a dedicated charger. If it is a PC, the device will limit the drawing current. If it is a dedicated charger, the device will draw more current to charge itself.
I am confused as to who is right and which charger should i be using.
Can someone enlighten me ?
Thank you very much.

Automobile Quick Charging Solution

What is the best solution for quick charging the Galaxy Nexus in an automobile?

I have started to use 12-220 volt converter so I can use wall chargers.

I have bought a few of the low profile car usb chargers but they were never recognized as an AC charge. Come to find out, it was the USB cable. I bought a usb charging cable from Amazon last week and it goes in the USB charger and the phone does not think it is a USB charge. I have not timed it but it is recognized the same as the wall charger.
http://www.amazon.com/gp/product/B003VYBCAY

ellisz said:
I have bought a few of the low profile car usb chargers but they were never recognized as an AC charge. Come to find out, it was the USB cable. I bought a usb charging cable from Amazon last week and it goes in the USB charger and the phone does not think it is a USB charge. I have not timed it but it is recognized the same as the wall charger.
http://www.amazon.com/gp/product/B003VYBCAY
Click to expand...
Click to collapse
+1 .. this solution has been working great for me, as well.

I've been getting 2.1A car chargers (look for ones for the iPad), most of the ones I had prior to this were 700mA or so and they can't keep up with my 1A phones. Be careful of dual port chargers advertising 2A, they may only be 1A each and may be "optimistic" about that rating. And don't worry about getting one rated for too much current, the Galaxy Nexus won't pull more than an amp no matter what the charger rating.

Some really good solutions here and thank you all for the help.
I'd really hate to use an inventer in my car just to maintain a clean install, so that really isnt an option for me.
Was really hoping to be able to use a off the shelf car charger with the correct pins to trick the GNexus into thinking that it was charging from a USB port, but the above solution should work well with using a socket USB charger.

I've never run into a car adapter that looks like a USB port, including the VZW charger with a spare port or the cheap 2.1A chargers I got from Amazon. My guess is that a charger not built correctly and leaving the data pins open only supports ~500mA anyway. Even if that's not the case I have a moral objection toward buying a cable to fix a design flaw in another cheap product - but that's just me

Grant H said:
Some really good solutions here and thank you all for the help.
I'd really hate to use an inventer in my car just to maintain a clean install, so that really isnt an option for me.
Was really hoping to be able to use a off the shelf car charger with the correct pins to trick the GNexus into thinking that it was charging from a USB port, but the above solution should work well with using a socket USB charger.
Click to expand...
Click to collapse
I've got a charger similar to http://www.ebay.com.au/itm/USB-Car-...ccessories&hash=item4ab18358f4#ht_1638wt_1392
All I had to do was undo the screws at the top, put a bit of solder between the middle usb pins, and my phone recognises it as a AC source rather than USB.

There has got to be a standard car charger on the market with the middle usb pins already soldiered!
I found this on Amazon which advertises itself as a rapid charging device.
http://www.amazon.com/gp/product/B000S5Q9CA

Grant H said:
What is the best solution for quick charging the Galaxy Nexus in an automobile?
Click to expand...
Click to collapse
Make sure the charger has the IC (rapid) chip. I use this one:
http://www.amazon.com/Motorola-Vehicle-Adapter-micro-USB-Charger/dp/B000S5Q9CA

I've heard that Motorola one mentioned a lot as a good one.
The nice thing about having the low-profile usb plug is (a) it is low profile, (b) I can use it to charge other devices. The charge-only cable is only about $4, so I had no issues buying it to work with this to charge as an AC charge over a USB charge.

Grant H said:
There has got to be a standard car charger on the market with the middle usb pins already soldiered!
I found this on Amazon which advertises itself as a rapid charging device.
http://www.amazon.com/gp/product/B000S5Q9CA
Click to expand...
Click to collapse
I have this one and it charges just like it does from the home outlet and its says "AC" charging. I bought another 8 for family and friends and they all love it.

I think I've figured out the disconnect, I've run into chargers that appear as a USB host which limits the charging to 500mA on previous phones I've had.
You guys are concerned about USB vs. AC charging mode. Of the chargers I've got, this one lists as AC while the rest as USB. However, the fact that the other chargers all work just fine keeping up with GPS+streaming music indicates that the USB vs. AC really has no bearing on the charge current delivered. I'd stay away from charge-only cables just because they'll get mixed in with your standard USB cables and you'll knock yourself out wondering why they don't work. On the other hand, if you really want AC in your battery info order the one I linked.

I keep it in my car... i think I've heard on other threads that USB charging doesn't keep up with GPS (for Directions). Any verify?
Sent from my Galaxy Nexus using XDA App

TheKaz said:
I keep it in my car... i think I've heard on other threads that USB charging doesn't keep up with GPS (for Directions). Any verify?
Sent from my Galaxy Nexus using XDA App
Click to expand...
Click to collapse
What's much more important is the rating on the power source. The GN can pull up to 1000mA, if your charger is only rated for 800mA (like many car chargers) it doesn't matter if it's in AC mode.

jdbower said:
What's much more important is the rating on the power source. The GN can pull up to 1000mA, if your charger is only rated for 800mA (like many car chargers) it doesn't matter if it's in AC mode.
Click to expand...
Click to collapse
makes sense.. the one I use has dual usb (1.0 and 2.1)

You went and gave me a project for the weekend, and once again science prevails over anecdotal evidence. I took each of my 5 chargers and hooked them up to a 12V power supply that measures current. I then recorded whether the charger reported AC or USB, for the ones with USB I modified a right-angle adapter to short out the data pins, and I measured the current. The contenders:
Verizon Wireless Dual Charger
XTG Dual Port Charger
Griffen Powerjolt Dual USB Charger
Griffen Portjolt Micro
CostMad Dual USB Charger
The VZW model was USB out the external port as I had tested before, however AC out the built-in cable which I hadn't bothered to test. It pulled 0.25A @12V via the USB port and 0.59A via the cable. Hmmm... A hole develops in my previous observation. While I had used this on a long car trip with no issues, it was via the built-in cable.
The XTG was new, I hadn't used it before as it's in the car I rarely drive. It reported USB and 0.22A. With the adapter to make it report AC it pulled 0.48A.
The pattern was set. I had expected the Griffen adapters to be built more appropriately but the dual charger reported 0.22A without the adapter and 0.42A with. I had used this without losing charge in the past so this was surprising to me, but it's possible I just wasn't drawing as much current because the screen was dimmer or something.
The compact Griffen adapter (which is great for a laptop bag, BTW) pulled 0.21A and 0.47A respectively.
The cheap CostMad adapter was the only one that performed well out of the box, both reporting AC and pulled 0.57A.
In theory, a perfect adapter should pull 0.42A. Anything more is waste, anything less means it's not keeping up. I have doubts about the Griffen 2x allowing for a full amp, but the VZW and CostMad chargers are pretty lossy. What's even worse is that I'm pretty sure the VZW charger is rated for 800mA (but I can't find an actual spec on it) which would mean that it pulled the most power for the least current. Not that this really matters unless you've got an electric car.
Sorry for misleading you earlier, I should have checked the other port of the known-good VZW charger and probably doublechecked the numbers on my other "known good" charger. Still hating cables that work for charging but not for data, I ended up modifying each of the chargers to short the middle pins (except for the VZW one). If I didn't have the soldering iron for this, I probably would have gone for some of these instead.

Grant H said:
There has got to be a standard car charger on the market with the middle usb pins already soldiered!
I found this on Amazon which advertises itself as a rapid charging device.
http://www.amazon.com/gp/product/B000S5Q9CA
Click to expand...
Click to collapse
CyberPunk7t9 said:
Make sure the charger has the IC (rapid) chip. I use this one:
http://www.amazon.com/Motorola-Vehicle-Adapter-micro-USB-Charger/dp/B000S5Q9CA
Click to expand...
Click to collapse
I'm using the same one and it works perfect. Charges even when GPS navigation is running.
Make sure you select Amazon as the seller though. I heard there are a lot of fake ones.

Grant H said:
There has got to be a standard car charger on the market with the middle usb pins already soldiered!
I found this on Amazon which advertises itself as a rapid charging device.
http://www.amazon.com/gp/product/B000S5Q9CA
Click to expand...
Click to collapse
+1 to those recommending this one. I have this exact model and it does indeed charge at the "AC" rate, about twice as fast as the "USB" rate.

TheKaz said:
I keep it in my car... i think I've heard on other threads that USB charging doesn't keep up with GPS (for Directions). Any verify?
Sent from my Galaxy Nexus using XDA App
Click to expand...
Click to collapse
The Motorola one will charge even when using GPS. I have a friend I bought one for that uses his GPS all day and loves the Motorola charger.

Are iPad chargers compatible with Galaxy Tab 10.1?

I picked up one of these chargers:
http://www.macally.com/EN/Product/ArticleShow.asp?ArticleID=326
which, in principle, should charge the Tab. It does charge it but it also does some strange things while plugged in:
1. Starts MTP USB mode
2. Completely messes up digitizer - I've installed TouchScreenTune and in the test area I can see when I touch, sometimes the perceived touch seems to rapidly cross the entire vertical area and in regular use it will activate the status bar when I touch anywhere.
I exchanged it for this one:
http://www.macally.com/EN/Product/ipod4show.asp?ArticleID=391
It doesn't have as high a wattage output but still higher than a standard USB charger so should charge faster.
I still get:
1. MTP USB mode
2. not quite as messed up digitizer - seems to be okay in normal use but when I test it in TouchScreenTune I can see that the perceived touch is very jittery. It's now jittery only to a small amount of error so it's usable, but something is going on.
I've also found the tablet completely non-responsive to touch a couple of times today (not plugged in) and eventually it comes back but behaves very slowly until I reboot. I don't know if this has anything to do with the charger or just a coincidence.
I'm concerned with the behaviour of the digitizer that these chargers are doing something bad to my tablet. These behaviours don't occur when I use the official charger. I was hoping to get something with multiple charging ports so I have less to carry and plug in when I travel.
Should I be concerned about use this charger? If so, other than the official Samsung charger, does anyone know of a compatible multi-port charger?
Thanks!

You might be looking at different effects caused by different things.
1) There are two different kinds of USB cables for the Galaxy Tab 10.1: a data cable and a charger cable. These are slightly different. Using a data cable will still allow the Tab to charge, but probably slower. But this can cause the MTP USB mode to kick in (but this also depends on the charger)
2) Some chargers go way above the normal 5 Volt. With most devices that is not a very big problem. But capacitive touch screens are very sensitive to that. That's most probably what you notive. I see the same if I use some cheaper chargers.
3) I don't think your touch screen is damaged by the use of these chargers. If that would be the case, it would probably malfunction all of the time and not occasionally. Chances are a lot higher that you installed some new software or widget that is behaving badly.

USB chargers designed for apple devices in principle will not supply more then 0.5A to non-apple devices.
Apple uses a special technique to signal to the USB charger to supply more power, while non-apple devices uses a different technique. And unfortunately all the charger manufacturers only seem to consider Apple.
So all those chargers proclaiming 2.1A that you can find on Amazon or eBay are all designed for Apple devices. And don't believe when it says on Amazon or eBay that Android devices are supported. Read the reviews and you will typically find someone with charging problems with a non-apple device.

USB chargers are basically all the same except for the amperage that they put out. The stock GTab will not charge very well unless the amperage is around 2A. If you root, you can install a tweak that allows the device to charge with any amperage but with the typical .5A charger it will take a lot longer than with a 2A version.
I use the charging pucks for my iPhone and my wife's iPad interchangeably for those devices and my GTab. They all work fine. The iPad puck puts out about 2A and is about the same as the one that ships with the GTab. Since the GTab version is on my desk, I also use it to charge a bunch of other USB devices such as my hands free car speaker and some wireless headphones. I just plug the appropriate cable into the puck. I have not experienced any problems and suspect that I could use my wife's iPad puck the same way. (I have not yet tried this).
I just ordered a couple dual 2A USB car chargers that allow two USB cables to be plugged in, each getting 2.1A. From what I have been able to discover, these devices will charge just about anything as long as the charging cable has a standard USB connector. They come from China on eBay for less than $3 ea.
I will follow up this post with a review when they arrive.
Bob

USB chargers are not all the same.
"Modern" Adapters that implement the USB Battery Charging Spec, short the middle two data wires (D- and D+), the device can use that to detect that it can draw up to 1.5A (instead of the 0.5A that you get from a regular port).
Apple instead using a different (non-standard) scheme where they communicate to the power supply using voltages, and where different voltages represent different Amperage (I don't know the exact details).
So power supplies sold for Apple devices, as far as I have seen, do not short the data wires and as such a non-Apple device will not draw more then 0.5A
*edit*
Just to add to this, because apple devices communicates with the charger over the two data wires using voltages, while devices that implement the USB Battery Charging Spec require the data lines to be shorted, the two implementations are incompatible.
What you could probably do, is crack open a 2A apple compatible charger and just short the D- and D+ and have a charger that will charge non-apple devices up to 1.5A. And it should also be possible to put a switch on the charger to switch between Standard and Apple charging mode. But if you mess up, don't come and complain to me!
Here is a nice video on how the apple charging works for the iPhone on youtube. But unfortunately this crap forum software won't allow me to post outside links.
Just do a google search for "reverse engineering apple charger"

I made some usb adapters that plug between any usb port and galaxy tab 7.0 plus usb
I made some usb adapters that plug between any usb port and your samsung galaxy tab 7.0 plus usb connector that allows charging from any usb port. I think it's the same for any galaxy tablet/phone. This way you can charge from any pc, or generic wall charger, any car charger, etc. If you're interested in one let me know. I can list them on ebay or some other site.
See pictures, nothing fancy but they work perfect with any charger and or usb port
Pic 1 is adapter
Pic 2 is adapter plugged into portable 12000mAh battery charger made for apple products
Pic 3 I added another adapter I made in between to measure amperage
Pic 4 is screen shot showing "AC" not "USB" and little batter icon without RED "X"

[Q] Can use ipad charger to charge galaxy note?

Hi bringing one charger around would be much convenient. Can i use ipad charger, with 2A output to charge galaxy note?
Tq.

Yes. I've charged mine with it many times.

Hey thanks...

Apple out of norms
Hi
Using a standard USB cable will get you a slow charge, even if the Ipad charger is very powerfull. This is because apple doesn't follow the rules.
Charging your Note may take 6 hours then.
To get fast charge, you need to modify your cable or charger, as stated in this thread : http://forum.xda-developers.com/showthread.php?t=1497864&page=2

jabab said:
Hi
Using a standard USB cable will get you a slow charge, even if the Ipad charger is very powerfull. This is because apple doesn't follow the rules.
Charging your Note may take 6 hours then.
To get fast charge, you need to modify your cable or charger, as stated in this thread : http://forum.xda-developers.com/showthread.php?t=1497864&page=2
Click to expand...
Click to collapse
The increased charge in this mod seems to work for charging via usb port, power from a pc. Charge from main ac lead still higher.
So does charging my Note with an ipad adapter + Note usb cable help increase charge since the ipad adapter has an 2A output??

I'll try to make it clear.
Using a common adapter or any pc USB II or ANY apple adapter will give give you a slow charge with a standard USB to micro-USB 4 wire cable.
This is simply because they can't usually deliver more than 0.5A. For apple, they have a specific standard out of the USB norm.
To go into fast charge mode, the gnote scans pin 2 and 3 of the USB link. If they are short circuited, the gnote tries to go into fast charge mode, and draws up to 1A.
The short circuit of data pins (2 and 3) is specified in the USB norm to state "this adapter can provide 1A"
Some adapters, such as the Samsung one I got with my gnote, already have these pin short circuited inside them and make your phone go into fast charge mode.
If you have an adapter able to supply 1A or more, such as your Ipad's, the simplest way to fast charge your gnote is to have a modified cable. No risk to harm your phone nor your adapter if you respect the wiring.
Sent from my GT-N7000 using Tapatalk

I think i understand now. Thanks so much Jabab.

jabab said:
I'll try to make it clear.
Using a common adapter or any pc USB II or ANY apple adapter will give give you a slow charge with a standard USB to micro-USB 4 wire cable.
This is simply because they can't usually deliver more than 0.5A. For apple, they have a specific standard out of the USB norm.
To go into fast charge mode, the gnote scans pin 2 and 3 of the USB link. If they are short circuited, the gnote tries to go into fast charge mode, and draws up to 1A.
The short circuit of data pins (2 and 3) is specified in the USB norm to state "this adapter can provide 1A"
Some adapters, such as the Samsung one I got with my gnote, already have these pin short circuited inside them and make your phone go into fast charge mode.
If you have an adapter able to supply 1A or more, such as your Ipad's, the simplest way to fast charge your gnote is to have a modified cable. No risk to harm your phone nor your adapter if you respect the wiring.
Click to expand...
Click to collapse
what i want to know is:
if the ipad charger is 2A, will the phone draw all that 2A or just 1A?
im asking because if it designed to work with a 1A charger - is the draw capped at 1A?

Hi
The draw of any phone is limited to its maximum power consumption ie phone consumption + battery charging.
I believe this draw is limited to 1A within the gnote.
Having a 2A charger only means it can provide up to 2A. It's the "pipe" size, in a way.
If there were a way to increase the gnote draw to more than 1A, by example in order to charge the battery faster while using the GPS, this could be :
Either telling the gnote, using a resistor on the 5th pin of the micro-USB plug.
Or using a specific app.
(or both)
I'm not aware of this possibility at the moment.
Sent from my GT-N7000 using Tapatalk

Jabab, thanks for ur valuable expert info. I've notice that charging my gnote with the ipad charger isnt much faster. But charging iphone with ipad charger does gives a great boost. What makes it possible with iphone?

Apple uses a not so different system to tell the iphone or the Ipad that it is connected to a powerful charger: the data pins are connected to the power pins through a ladder of resistances.
I see one main advantage to this: apple could change the resistances values inside the charger to indicate to the device if it is an 1A, 2A or any other current charger.
The main drawback is that this system is compatible with nothing but... Apple devices. This why you get a slow 0.5A charge with a 2A capable Ipad charger.
Sent from my GT-N7000 using Tapatalk

I found the original thread where I learned all this. It may be much clearer than my own explanations.
http://forum.xda-developers.com/showthread.php?t=1384253
I believe though that you need a 1A (1000mA) at least charger to do the indicated mod on the charger for use with a Galaxy Note.
Sent from my GT-N7000 using Tapatalk

Do I need a new USB cable or is there an issue with my phone?

I just got the Galaxy S 4 the other day. It didn't come with a USB cable so I used an old HTC micro-USB cable. Even though the cable worked with my HTC phone, it doesn't exactly work with my Galaxy S 4. I have to move the cable in a certain way to get it to charge or connect, otherwise it doesn't work.
I was able to charge my phone using a micro-USB charger for a bluetooth device (trickle charge, took 12 hours to charge), but obviously this isn't ideal. So is there something wrong with my phone, or just my cable? And what type of micro-USB cable should I get that might work?

It doesnt come with usb ??
Charger works as USB too.
Htc cable doesnt work on samsung phone. Motorola does.
Sent from my SGH-M919 using xda premium

I swapped it with someone for an HTC One and they didn't have a cable.
Sent from my SGH-M919 using xda app-developers app

kgor93 said:
I just got the Galaxy S 4 the other day. It didn't come with a USB cable so I used an old HTC micro-USB cable. Even though the cable worked with my HTC phone, it doesn't exactly work with my Galaxy S 4. I have to move the cable in a certain way to get it to charge or connect, otherwise it doesn't work.
I was able to charge my phone using a micro-USB charger for a bluetooth device (trickle charge, took 12 hours to charge), but obviously this isn't ideal. So is there something wrong with my phone, or just my cable? And what type of micro-USB cable should I get that might work?
Click to expand...
Click to collapse
It isn't your usb cable. You need a charge that output 2A at 5V to charge the S4 at decent speed. Computer's USB or typical 5V USB chargers will not do.

Just FYI when I use an older usb cable other than the samsung one, my charging time increases. So using the right USB cable matters. I use an app called Galaxy Charging Current Lite to determine my charging amp with other cables and other wall and car chargers. Very useful app. When using the samsung usb cable with the wall adapter I get 1900 and I can see the battery percentage go up faster. Using an older usb cable with the samsung wall adapter I get about 460 and battery percent goes up slowly. Try the app out and see what you get.

First thing I'd be doing is complain to T-mobile or Samsung. Both GS4s I've received (one on launch, one from insurance) came with the USB cable and charger ready to go.
Next, you need 2A @ 5V, but ya need the right power brick to supply that.
and most likely using older/newer/non-Sammy cables and charge time increasing is because the cables use a smaller gauge wire (like 28 or 30 AWG IIRC) rather than say, 24 or 20 AWG (keep in mind that the smaller the number the bigger the conductor, and larger numbers have smaller conductors). Even with the right power brick, the USB cord still matters; I remember on my Nexus 7 that unless you used its cable charging was either sluggish or non-existant. (FYI the Nexus 7 cable should work with the GS4, I use it for file transfers o my computer and when I did all my rooting.)
also I personally use the battery monitor widget on my Nexus 7 to monitor voltage/current input/output. I may consider putting it on my GS4.