Database Develop

[Q] Making an external battery charger.

Hi there!
My brother just bought me a spare battery. Well it still needs to be charged after usuage. The thing is I have to swap the batteries everytime I used them both. The solution is to buy a cradle to charge it but these are kinda expensive.
My solution would be to build my own charging cradle. But I lack the knowledge of electricity skills to succesfully making such charger without blowing up my battery. Therefor I'm asking the community on XDA for help!
Well this is what I need:
- Battery has 3 connectors: + and - and on in the middle but i dont know what that is.
- I have a usb cable with 4 wires (black/red/green/white)
- I want to connect the usb connecter to my PC or AC adapter and the wires to my battery.
This way I can charge both my HD2 and the spare battery at the same time.
The question is, is this possible and if yes, can this be done just like that or do I need transistors or conductors (or whatever they may called). It needs to be safe, I dont wanna blow up my battery or my AC adapter nor my PC...

Do not even contemplate it.
It is clear that you do not know enough about batteries.
A quick google for desktop chargers came back with one for only £30

For 25quid i got a spare battery, desktop charger and 2 screen protectors from e-bay. Carnt go wrong at that price

I know that the AC adapter converts the input of electrical energy to my phone, I believe my phone does it to my battery too (thats where I'm not too sure).
All I need to know is if I can charge the battery safely when connecting the red wire to the + and the black wire to the - side of the battery... (The green and white wires are data)
I'm not to sure because the AC adapter has a different output than the PC USB output. Although the USB dilivers a tiny bit less voltage it delivers a significant less amount of Whats (or Amps) Basicly that means it just takes longer for the USB to charge as long as the voltage remains identical. (The USB delivers less voltage but the effect on damaging the battery is minimal because the difference is discardable)
My actuall question was: can I connect my battery directly to the AC adapter or do I need to convert the electical energy again (if my phone does a second convert after the AC adapter).

You can find chargers on eBay for less than 5usd. Buy one or you will fry your battery.

VerusAmos said:
I know that the AC adapter converts the input of electrical energy to my phone, I believe my phone does it to my battery too (thats where I'm not too sure).
All I need to know is if I can charge the battery safely when connecting the red wire to the + and the black wire to the - side of the battery... (The green and white wires are data)
I'm not to sure because the AC adapter has a different output than the PC USB output. Although the USB dilivers a tiny bit less voltage it delivers a significant less amount of Whats (or Amps) Basicly that means it just takes longer for the USB to charge as long as the voltage remains identical. (The USB delivers less voltage but the effect on damaging the battery is minimal because the difference is discardable)
My actuall question was: can I connect my battery directly to the AC adapter or do I need to convert the electical energy again (if my phone does a second convert after the AC adapter).
Click to expand...
Click to collapse
Watts not Whats
Simple answer: No you cannot connect your battery directly to the AC adaptor.
Detailed answer:
The USB port of a computer/AC adaptor provides approx 5V and a variety of currents depending on what the USB lead is plugged into.
This 5V goes to the phone.
Inside the phone is the battery charging circuit, this detects the level of charge in the battery, controls the voltage and current going to the battery to stop it releasing too much hydrogen which would cause the battery to swell and explode (look on youtube for lithium polymer battery fires).
If you think you can create a charging circuit (including selecting the right ICs and programming them) without burning yourself in a hydrogen/lithium fire, be my guest.

Incapable of making an external battery charger...
Here I am trying not to be a complete idiot and then I go and spell watts the wrong way...
But tnx for the replies, that was all I needed to hear... I guess I'll be swapping batteries after all untill I find a cheap external battery charger...
Cheers!!!

Amzer makes a very nice cradle with charging slot for your spare battery. I got mine for $28USD. I'm not going to provide the link to the outfit I bought mine from because they weren't the best of suppliers to buy from. But the Amzer cradle works very well. Downside is that you cannot use it if you have a case for your Leo that wraps around it, and is designed to stay on. Leo must be caseless to fit into the cradle. But even if you don't use the cradle as a cradle, it does have the ability to charge your spare battery.

[Q] Compatibility with car charger on 1.5A and 5V

Hi,
a friend of mine have gifted to me a car charger that is incompatible with my Legend, because is miniusb (with output: 5V - 1.5A) and the regular charger in bundle with the phone is microusb with output: 5V - 1A.
Can I use the car charger, with a differte cable (the car charger can use usb cables), or the current in output is to much for the phone?

It doesn't actually matter how powerful the PSU (power source unit) is, even if it was 5V / 10A you could still use it... To put it to easy talk, the phone will just take what it needs. The important parameter is Voltage, which is OK - 5V

Dr.Romca said:
It doesn't actually matter how powerful the PSU (power source unit) is, even if it was 5V / 10A you could still use it...
Click to expand...
Click to collapse
That's not quite true. The power does matter, but only in a limited way. The voltage (volts) must match. The current (amps) or power (watts) rating of the supply must be at least that which the device draws.
So in this case; yes, you are absolutely fine. You just need an adaptor to make the plug fit.
My work phone has a mini-USB socket, but requires 1.5A to charge successfully, which is three times as much as standard USB. My personal phone has the same socket, but will charge when connected to a conventional USB host like a laptop, which only supplies up to 0.5A. I can use any USB charger with my own phone, but I can only charge my work phone from its own charger.
Apparently I've not made enough posts to include links, but you can google "Charging Batteries Using USB Power - Maxim" and click on the first link, as long as you don't mind reading a moderately technical document.

Don't nitpick I'm an engineer so I know how these things work end to end, If you have power and a good charger (not meaning the car charger, but the actual charging circuit handling the battery charging inside the phone) you can charge even from 5V / 200mA It'll just take more time, of course you'd have to add more than the phone consumpts, but if you do that you're basically OK...
What you're referring to is USB charging, we all know USB doesn't have to have full 5V but in case of charger, there will be 5V...(possibly even more when open)

I have this car charger with 5V and 1000mAh
http://www.ansmann.de/cms/de/consumroot/chargers-and-power-supplies/universal-chargers/carcharger-micro-usb.html
and i must say it is worse than the Original charger for the Wall outlet from HTC -- it takes about twice as long to charge the phone.
And when i use my phone for Navigation it even slowly discharges the phone - which is truly annoying!
EDIT:
I did some research: on original HTC Chargers the Data+ and Data- pins on the micro-USB-connector are short-circuited to tell the HTC-Phone that it connected to an original charger - only when the phone realizes this, it charges with 1000mA!!! Otherwise it only charges with the USB-specificated 500mA
You can easily check this when you charge your Phone with a 3rd-Party charger, go to:
Settings-> Telephone-Status -> Battery
Here is usually written charging (USB)
only with original chargers you get "charging" (AC)
I opened the connector of my Car-charger and short-circuited the Data+ and Data- --> Now it says charging (AC)
I still have to test if charges faster now, and charges the phone while navigation - because until now it discharges while navigation, despite being connected to the Car-charger.
So to say it short: If you want to quickly charge your phone in your car buy a original HTC Car charger, or short-circuit a 3rd-Party one.

f4b1ck said:
Hi,
a friend of mine have gifted to me a car charger that is incompatible with my Legend, because is miniusb (with output: 5V - 1.5A) and the regular charger in bundle with the phone is microusb with output: 5V - 1A.
Can I use the car charger, with a differte cable (the car charger can use usb cables), or the current in output is to much for the phone?
Click to expand...
Click to collapse
don't worry you can charge your phone with no problem
i have the same 5V 1.2 A ,it's charging with no problem

It's good to have stornger charger. Probably you wil be able to charge your phone faster But it always have to be 5V.

USB charging in car?

Iam using the Dell Streak 7 as a sat nav system in the car. Ive tried to charge it up on the usb car adapter but it seems to loose its charge over time, making the D7 unusable for the purpose of a sat nav. Am i doing something wrong or is there a special usb car adapter for the job?
Thanks, David.

Does it say it's charging when plugged in?
Depending on how powerful your charger is it's likely that it's draining faster then the charger can provide. At best on my s5 it's just barely faster then the charger and the s7 needs more power then that.

Thanks for peply, yes it states it is plugged in. I came to the same conclusion. Wonder if there are any other chargers that have more juice.

diddy64 said:
Thanks for peply, yes it states it is plugged in. I came to the same conclusion. Wonder if there are any other chargers that have more juice.
Click to expand...
Click to collapse
There are several that will do the job. Just look for specs that include putting out 5.5 volts and 2 amps. Several of the chargers that are made for the iPad2 will work. And you may want to install a lighter adapter that you can wire directly to the battery that will allow up to 2 or 3 amps from each port

Most standard USB ports do not put out enough power to charge the DS7. The best bet is to use a inverter that plugs into your cigarette lighter and then plug the charger into that, not just the USB cable.
http://www.amazon.com/Power-Inverter-Charger-Portable-SmartPhones/dp/B00144KS6W

I use this setup:
Bestek Adapter
Trans4m lighter adapter
The Bestek I have wired to the battery so I have no fuse problems with lighter, and with that I can charge either my iPad2 or my Streak7, IF I need to charge both, then I plug the Transform adapter into the Bestek and can then charge BOTH devices, the Ipad2 AND the Streak7 and a couple of other things if need be

Thank you guys, this gives me alot of hope. Once again you all get my thanks.
Cheers,
David.

Yea, like they previously stated not all chargers are created equal.
Unless it states it's a tablet/ipad charger you cant assume it's doing 2+ amps. Most phone/lower end ones can only do 500mA/1A.
Realistically you'd prob need at least 2 amps to get a net gain while using gps/anything demanding. But I dont know if it would even try and draw above that if given the chance. [email protected] is what the bundled wall charger does and can accept up to 5.5v (as it's still within the +/-10% tolerence of the usb spec, but just barely)

My fully charged stock S7 WiFi running 514 draws only 45-70mA. Maybe starting fully charged would help?

wptski said:
My fully charged stock S7 WiFi running 514 draws only 45-70mA. Maybe starting fully charged would help?
Click to expand...
Click to collapse
I don't know anything about how it works, but I imagine tablets are wired to know when they are receiving the correct amount of input. For instance, if you connect your Streak 7 to a powered USB hub that only puts out 5 volts, it won't charge nor will it charge when connect via usb to the PC, it has to be receiving 5.5 volts and 2 amps before it will let itself receive charge. I have an iPad that is the same way and have noticed all the tablets I have had my hands on are the same, Galaxy Tabs, Transformers, Xoom... all those have to receive higher numbers to charge. So you have to have a cigarrette lighter adapter that puts that out, if it's for a cell phone it won't do anything for it

cdzo72 said:
I don't know anything about how it works, but I imagine tablets are wired to know when they are receiving the correct amount of input. For instance, if you connect your Streak 7 to a powered USB hub that only puts out 5 volts, it won't charge nor will it charge when connect via usb to the PC, it has to be receiving 5.5 volts and 2 amps before it will let itself receive charge. I have an iPad that is the same way and have noticed all the tablets I have had my hands on are the same, Galaxy Tabs, Transformers, Xoom... all those have to receive higher numbers to charge. So you have to have a cigarrette lighter adapter that puts that out, if it's for a cell phone it won't do anything for it
Click to expand...
Click to collapse
The voltage is constant but current isn't. It won't know how much current is available unless it asks for it. It's like a 2A fuse, you can draw up to 2A, no more.
Even with a fully charged battery it'll show charging at 98% for a short time and that's when I saw the higher 70mA but I'm not sure if it's in the CC or CV part of a Li-Ion charge cycle but I'd guess CV because it's less than 100mA.

My bad thinking measuring AC input current instead of DC current since this thread is about USB power.
Used a cheap ReTrak USB extension cord that loses connections to seperate the wire to measure DC current. My fully charged S7 showing 100% charge still draws 150mA after hours of being plugged in. Since Li-Ion cells normally don't use a constant trickle charge, I "assume" something draws on the battery all the time along with the indicator light and buttons.
Booting up it draws a little over 1A, fully charged while booted up, it draws around 600mA. While charging and powered up, it draws 914mA. Charging while off, it draws 1160mA. Far from 2A.

wptski said:
My bad thinking measuring AC input current instead of DC current since this thread is about USB power.
Used a cheap ReTrak USB extension cord that loses connections to seperate the wire to measure DC current. My fully charged S7 showing 100% charge still draws 150mA after hours of being plugged in. Since Li-Ion cells normally don't use a constant trickle charge, I "assume" something draws on the battery all the time along with the indicator light and buttons.
Booting up it draws a little over 1A, fully charged while booted up, it draws around 600mA. While charging and powered up, it draws 914mA. Charging while off, it draws 1160mA. Far from 2A.
Click to expand...
Click to collapse
I understand that, but you are missing the point, if the internal wiring of these tablets don't receive the 2A they want they WILL NOT even begin to charge. I tried literally dozens of chargers when I first got my S7, spent a couple hundred bucks actually, and none of the chargers not meant for larger devices won't work, and what those chargers all had in common, 2A output

The S7 can and will draw off low capacity ports, it just wont admit to charging unless it's at least 1A as it's just that.
I've had my S7 charge off a 500mA port on my pc at the rate of like 1%/hour while sleeping. As it's barely gaining even while idleing it's not really charging in the literal sense, but it's definitely charging in the technical sense.
Are your data lines shorted together? I believe most high draw devices wont attempt to pull 2A unless it detects that it's on a high draw charger (which I think do this to indicate it as such)

cdzo72 said:
I understand that, but you are missing the point, if the internal wiring of these tablets don't receive the 2A they want they WILL NOT even begin to charge. I tried literally dozens of chargers when I first got my S7, spent a couple hundred bucks actually, and none of the chargers not meant for larger devices won't work, and what those chargers all had in common, 2A output
Click to expand...
Click to collapse
I don't know why your various chargers didn't work but it doesn't seem to be because of current. It didn't charge at 2A or even close to that.
If what your saying correct, why was I able to charge at less than 2A then? Could this be a ROM issue? I only had Froyo for a few hours but I've read that it didn't support USB charging which came with HC but it only charges with the S7 OFF.
It's possible that the demand went higher and I just didn't see on my current clamp meter. I'll have to try a current clamp and a scope to see if I missed a peak level.
Also what we are refering to as the charger might not be a charger but only a power supply and the actual charging circuit is in the S7.
I did notice one odd thing though. The green LED lights up at around 90% battery level and it's still charging. I downloaded a battery app which read the same level.

wptski said:
I don't know why your various chargers didn't work but it doesn't seem to be because of current. It didn't charge at 2A or even close to that.
If what your saying correct, why was I able to charge at less than 2A then? Could this be a ROM issue? I only had Froyo for a few hours but I've read that it didn't support USB charging which came with HC but it only charges with the S7 OFF.
It's possible that the demand went higher and I just didn't see on my current clamp meter. I'll have to try a current clamp and a scope to see if I missed a peak level.
Also what we are refering to as the charger might not be a charger but only a power supply and the actual charging circuit is in the S7.
I did notice one odd thing though. The green LED lights up at around 90% battery level and it's still charging. I downloaded a battery app which read the same level.
Click to expand...
Click to collapse
You were able to charge because your charger was CAPABLE of outputting 2A at least... try charging with one that CAN'T put that out and you should find that the Streak will not charge, on ANY ROM has been my experience, custom or stock

cdzo72 said:
You were able to charge because your charger was CAPABLE of outputting 2A at least... try charging with one that CAN'T put that out and you should find that the Streak will not charge, on ANY ROM has been my experience, custom or stock
Click to expand...
Click to collapse
Capable is the magic word here. The wall wart isn't putting out 2A from what I've seen, unless it does for a split second at the start which I'm going to look into.
Most wall warts at whatever their rating is put out a higher voltage with no load and slightly higher than its marked voltage under a load. If it required [email protected] max., you used a [email protected], S7 needs more current, the voltage would decrease. What's been stated here might be that the voltage was being pulled down and that's why the S7 wouldn't charge, not "really" the 2A issue.
I have a battery pack/cell load testing device used on RC stuff that connects via USB port for its graphic software. There were issues with certain Dell laptops that had a low voltage at their USB ports.

Maybe starting fully charged would help?
I have the OEM T-Mobile car charger and I've found that if I have a full charge before plugging the Streak into the charger it maintains a full charge for as long as I'm driving/using it. Otherwise, with a less than full charge I've watched it slowly discharge even though it's plugged in and is charging.
FYI: I also have a top of the line car charger for an iPad2 that charges the iPad no matter what charge level I plug it in. This iPad charger has a USB port which I have plugged the Streak USB cord into and it also doesn't keep up with the Streak's discharge if the Streak isn't a full charge to begin with. Kind of strange because I would think the iPad would draw more than a Streak. (the iPad isn't plugged in at the same time the Streak is charging)

DCoop said:
Maybe starting fully charged would help?
I have the OEM T-Mobile car charger and I've found that if I have a full charge before plugging the Streak into the charger it maintains a full charge for as long as I'm driving/using it. Otherwise, with a less than full charge I've watched it slowly discharge even though it's plugged in and is charging.
FYI: I also have a top of the line car charger for an iPad2 that charges the iPad no matter what charge level I plug it in. This iPad charger has a USB port which I have plugged the Streak USB cord into and it also doesn't keep up with the Streak's discharge if the Streak isn't a full charge to begin with. Kind of strange because I would think the iPad would draw more than a Streak. (the iPad isn't plugged in at the same time the Streak is charging)
Click to expand...
Click to collapse
The S7 must run some check before it tries to charge . Whatever it is the OEM supplied power supply passes the test.
What's the specs on your two power supplies?

Just remember if you dont have the same 2A for charging in the car. You cannot charge the streak while its TURNED ON. Same with USB charging, just turn the streak OFF, then charge. It will work. =)
Otherwise, Id get a DC to AC converter for the car, plug in your normal adapter.

NC charger

I was wondering where to get a charger for my NC, whether it be car or home, that will not be 30 like in the stores.

smayer85 said:
I was wondering where to get a charger for my NC, whether it be car or home, that will not be 30 like in the stores.
Click to expand...
Click to collapse
Just search for ADP-H01 on the web. I have seen them as low as $16.

Good suggestion leapinlar, looks like I'm gonna acquire a spare soon.

The NC is a mature product, and anything worth talking about has been talked out. Search these NC forums (or just Google in general) for "nook color charger".
Here's one that's interesting: The OS makes a difference. Those using CM7 can charge using any 2.0 or 2.1A charger, with any cable (presumably of sufficient gauge to carry 2A). Those using stock ROM must use OEM charger & cable.
http://forum.xda-developers.com/showthread.php?t=1002332
I'm not sure about stock, since I converted my NCs OOB. But my experience (using CM7) is same as the OP in above-linked thread. I can charge with any 2A charger and standard cable.

e.mote said:
The NC is a mature product, and anything worth talking about has been talked out. Search these NC forums (or just Google in general) for "nook color charger".
Here's one that's interesting: The OS makes a difference. Those using CM7 can charge using any 2.0 or 2.1A charger, with any cable (presumably of sufficient gauge to carry 2A). Those using stock ROM must use OEM charger & cable.
http://forum.xda-developers.com/showthread.php?t=1002332
I'm not sure about stock, since I converted my NCs OOB. But my experience (using CM7) is same as the OP in above-linked thread. I can charge with any 2A charger and standard cable.
Click to expand...
Click to collapse
Yes, you can charge, but not at the full rate. The charging block must have the two center pins shorted (d+/d-). Some charging blocks have that and some do not. If they are shorted, the nook might allow the block to deliver the full 2+ A rated on the block. But the cable must be able to deliver that much current. Only the stock cable can do that. It has extra pins (a total of 12) in the nook end of the connector to deliver that much. Regular microUSB cables do not have those pins. That is why nook cables have an end that look longer than standard cables. So the charging circuits in the nook sense the shorted data pins and the extra pins in the cable, then it turns on full charging. It does this for all roms. If it does not detect those two conditions, it assumes you are connected to a USB port and limits charging current to 500MA regardless of block capacity.

leapinlar said:
Yes, you can charge, but not at the full rate. The charging block must have the two center pins shorted (d+/d-). Some charging blocks have that and some do not. If they are shorted, the nook might allow the block to deliver the full 2+ A rated on the block. But the cable must be able to deliver that much current. Only the stock cable can do that. It has extra pins (a total of 12) in the nook end of the connector to deliver that much. Regular microUSB cables do not have those pins. That is why nook cables have an end that look longer than standard cables. So the charging circuits in the nook sense the shorted data pins and the extra pins in the cable, then it turns on full charging. It does this for all roms. If it does not detect those two conditions, it assumes you are connected to a USB port and limits charging current to 500MA regardless of block capacity.
Click to expand...
Click to collapse
I have found that as long as I have my charger cable, I can use any "block" to charge. I generally will use my IPAD block and that charges it just as quickly. So instead of having to spend 30 bucks for a new nook block, I can just use my cable and a different block. its very convenient.

IPAD bricks provide 2.0A and the B&N ones are rated at 1.9A. It boils down to the (semi-)proprietary cable.

ufkal said:
I have found that as long as I have my charger cable, I can use any "block" to charge. I generally will use my IPAD block and that charges it just as quickly. So instead of having to spend 30 bucks for a new nook block, I can just use my cable and a different block. its very convenient.
Click to expand...
Click to collapse
iPad chargers also have the data pins shorted.

leapinlar said:
Yes, you can charge, but not at the full rate. The charging block must have the two center pins shorted (d+/d-). Some charging blocks have that and some do not. If they are shorted, the nook might allow the block to deliver the full 2+ A rated on the block. But the cable must be able to deliver that much current. Only the stock cable can do that. It has extra pins (a total of 12) in the nook end of the connector to deliver that much. Regular microUSB cables do not have those pins. That is why nook cables have an end that look longer than standard cables. So the charging circuits in the nook sense the shorted data pins and the extra pins in the cable, then it turns on full charging. It does this for all roms. If it does not detect those two conditions, it assumes you are connected to a USB port and limits charging current to 500MA regardless of block capacity.
Click to expand...
Click to collapse
In my experience there are actually 3 possible max charging rates into the Nook Color
1) USB mode where a charger / cable doesn't have shorted data lines (including PC) - Max 500 ma
2) AC mode (half) where a charger does have shorted data lines but a standard USB cable is used - Max 1000ma
3) AC mode full where a charger has shorted data lines and a Nook proprietary cable is used with the extra power pins - Max 1900ma

>In my experience there are actually 3 possible max charging rates into the Nook Color
How did you measure the differing DC current? Clamp meter? In-line resistor?

Battery Widget in the Play Store will tell you near real time.
Rodney

rhester72 said:
Battery Widget in the Play Store will tell you near real time.
Rodney
Click to expand...
Click to collapse
That's what I have used and it seems to tally well with rate of charge of the battery. It indicates AC or USB charging (shorted / non-shorted data lines) and showed 1000mA in AC mode with standard USB cable as opposed to 1900 with Nook cable.

>Battery Widget in the Play Store will tell you near real time.
Can you provide the developer name? There are many battery widgets, and those I've tried don't indicate charging level. TIA.

e.mote said:
>Battery Widget in the Play Store will tell you near real time.
Can you provide the developer name? There are many battery widgets, and those I've tried don't indicate charging level. TIA.
Click to expand...
Click to collapse
I use Battery Monitor Widget Pro by 3C. It has a history screen that shows charging current vs time. I think they have a free version.

Thanks for the tip. Battery Monitor Widget is a better monitor than those I've tried, although it overloads on detail. However I think the +/- mA reading is a net reading (charge - discharge rate) rather than the charge current by itself. Since the unit needs to be on for the widget to run, it's probably not possible for it to get just the charge reading.

+1 for the battery information widget. I actually like all of the information.
Sent from my Thunderbolt using Tapatalk 2

Want faster charging/Device discharging while charging/not charging? Read within!

Background
Hi all, I, for a very short period of time was suffering from the problem of my phone DISCHARGING while it was charging. This made no logical sense to me until I did some research, which I will detail below.
How USB Power works (Roughly)
Firstly let's discuss USB power provisioning. Strictly speaking, the specifications say that any given USB port should provide a maximum of 500mA (or 0.5A) at 5 volts. *Don't shoot me electronics guys, I'm simplifying for ease of explanations sake*. Imagine that ampage as the actual force of the charger, how quickly it can ram power into your phone. Like the rate of flow on a pipe.
The beginning of the problem
This was all fine and dandy when all USB was really used for was Keyboards, Mice, Memory, etc, low current draw devices. Something else I should mention here is that the Ampage that a port CAN provide is not the Ampage it DOES provide - the device draws a certain Ampage and if the USB controller agrees it outputs said Ampage. Later, when USB was beginning to be used for more power hungry applications, ie External hard drives, these required more power than the port could (In theory) provide. However, most more modern motherboards/USB controllers were more than capable of supplying plenty more Ampage if it was requested. This was breaking the specification but not in any massively dangerous way so as such nothing bad happens.
This is where we get to the actual issue people are experiencing here. The Nexus 4 is a standards compliant device in the respect that it seems to only draw 500mA from any USB port no matter what it's potential, unless it's an AC Wall wart. If you're experiencing problems with wakelocks (see XDA) and other things, this causes your phone to draw more than 500mA which means your phone actually discharges while it's charging! Terrible!
This is quite easy to get around, but again I'm going into detail so let's explain how the phone tells the difference between a dumb wall wart and a USB controller. Easily! The USB controller obviously makes use of the data pins found within the USB cable, whereas a wallwart just (almost always) shorts them out. The Nexus 4 can detect this short, and as such draw more power *While still in quotation marks staying in spec*.
The root problem is not with how the N4 is charging, it's with the wakelock you're experiencing which is causing the phone to draw so much power while the screen is off. While the screen is off and the phone is in Deepsleep (A CPU state where it uses very little power) - it should draw no more than 50mA leaving 450mA for charging the battery, but you guys are probably experiencing a wakelock of some sort.
Solutions to the problem or How to break a specification for the good of mankind
The simple solution is to install this app: https://play.google.com/store/apps/details?id=com.rootuninstaller.batrsaver
This forces the device into a Deep sleep when the screen goes off by killing applications and turning off all internal chipsets that have wakelock capability, most commonly networking on the Nexus 4. This will allow your phone to charge (slowly) off USB without an issue. Another common wakelock is when the device is picked up by your desktop as a media device. The USB controller inside the Nexus 4 forces a wakelock which keeps it from charging. Stupid design, I know.
* A more hackish solution is to install Francos kernel, buy his app, and tick the Fast charging option in the kernel settings dialog. This will force the phone to think that everything is an AC adaptor and will force the phone to draw as much current as it can from the USB port (which on most modern motherboards is fine, and results in extremely quick charging).
* An even simpler solution than all this is to just use a 'USB Charging cable' - this is simply a cable that does not have the Data pins, and as such does exactly the same as what enabling USB fast charge above does. http://www.ebay.co.uk/itm/Micro-USB...487076?pt=PDA_Accessories&hash=item51a465d124
If you live near a Poundland store here in the UK they sell a 4 in one USB cable type thing which turns 1 USB port into Ipod sync connector, Nokia connector, MicroUSB and MiniUSB, and this doesn't have the data pins and as such is excellent.
One final point, an excellent app for monitoring whether your device is actually charging or not and how quickly is Current widget: https://play.google.com/store/apps/details?id=com.manor.currentwidget&hl=en
This widget will tell you how much Ampage is going into or leaving your battery. If the battery icon is green, then it's discharging, if it's black/white then it's charging. The bigger the number, the faster the discharge/charge. This is an extremely easy way to test speed of chargers too.
Recommendations
Another solution, just use an AC Wall wart - they're cheap as hell and the one supplied with the Nexus 4 is an extremely fast charging one. Shame I've gone and lost mine.
A way to roughly monitor charging current draw
I'd also recommend you install https://play.google.com/store/apps/details?id=com.manor.currentwidget&hl=en and monitor, if the battery is green while charging it's discharging and you need a more powerful charger/to figure out what's causing your phone to use so much power.
General good values in Current Widget
I generally saw a max draw of about 750mA for charging (not including draw for powering the device, the Nexus 4 can draw more power to charge and power the device) on my old Rev10 first generation Nexus 4. On my new Rev12 board I'm noticing this increase to about 850mA.
Are higher amperage chargers any benefit to anyone?
Yes and no. You will not notice faster charging unless you use your device while charging. Your nexus will draw as much power as it needs to power the phone while charging at the fastest rate. For example on the stock 1.2a charger
1200mA | 800mA goes to charging 400mA goes to powering the phone idling
Let's say you start a stability test. Your phone will obviously be using a lot more power so this will happen
1200mA | -600mA goes to charging and 1800mA goes to powering the phone stability testing
That minus value above may look strange! Let me explain. If the phone needs more power than the charger can supply, it will draw from the battery. That's the minus number.
If you have a higher ampage charger like for example a 2.5a charger
2500mA | 800mA goes to charging 400mA goes to powering the device
Stability testing
2500mA | 700mA goes to charging 1800mA goes to powering the device
Can you see the difference?
DISCLAIMER: I am not an electronics engineer nor do I claim to be, I am simply a hobbyist and this is what I've found to be the case. Please correct me if I've made any mistakes, I want to learn.

Thanks!
Thanks so much for this post. It's very helpful.

kn100 said:
Another common wakelock is when the device is picked up by your desktop as a media device. The USB controller inside the Nexus 4 forces a wakelock which keeps it from charging. Stupid design, I know.
Click to expand...
Click to collapse
This isn't true for everyone then as mine connects and charges just fine off of my laptop and desktop when connected as a media device. In fact its on my laptop right now charging, gone from 68% to 81% in about 30 minutes and it shows connected as a portable media player.

Great info! Thanks for writing this!
In certain use cases the Nexus4 discharges faster than it charges and this is a very useful guide.
I use my phone for navigation in my car and having the GPS on and the screen at high brightness
drains the battery faster than the 0.5A car chargers can supply. Car chargers rated for 2.0A work well.
I haven't tried a 'USB charging cable' with the data pins shorted, it may work as well.

-Mindroid- said:
Great info! Thanks for writing this!
In certain use cases the Nexus4 discharges faster than it charges and this is a very useful guide.
I use my phone for navigation in my car and having the GPS on and the screen at high brightness
drains the battery faster than the 0.5A car chargers can supply. Car chargers rated for 2.0A work well.
I haven't tried a 'USB charging cable' with the data pins shorted, it may work as well.
Click to expand...
Click to collapse
was over in Nexus 7 forums and the 4.2.x kernel should have solved the problem at least for having to use shorted cables. have to wait and see if 4.2.2 brings any more changes.
http://forum.xda-developers.com/showthread.php?t=1984838
Section 6 in this link is about power supplied through USB
http://en.wikipedia.org/wiki/Universal_Serial_Bus
I can't tell if we have an updated kernel allowing faster usb charging as I'm limited by the power output of the usb port in my laptop. The output (5V at 500mA max) is controlled by the laptop (USB Standards) and it doesn't matter what the phone or cable is capable of as that's the max it will give out and that's about what I'm charging at. If I had a dedicated charging port in my laptop then it would be different and I could see if its able to draw more power. I have a 1.0 amp port in my car and it does charge at the higher amperage, I would assume it would do the same thing if I had a 2 amp usb port in the car. So I think the stock kernel has the fast usb charge built in it just depends upon if you have a usb port capable of providing a faster charger, it has nothing to do with the cable as I'm using a standard unmodified micro usb cable and its able to draw the max a usb device is able to put out.

thanks
thanks for a great detailed post!!!
I have the same trouble with my N4 when I was charging while using my phone...
I find it very slow... I guess I've been spoiled by my previous iPhone (which charges fairly fast)....
i might be stating the obvious but I find the phone charged "a lot" faster when it's OFF
if you are running low with your battery and need a quick 10 min charge, just do yourself a favour by turning off your phone...
the difference is quite significant!

kzoodroid said:
This isn't true for everyone then as mine connects and charges just fine off of my laptop and desktop when connected as a media device. In fact its on my laptop right now charging, gone from 68% to 81% in about 30 minutes and it shows connected as a portable media player.
Click to expand...
Click to collapse
Yup, me too. It only discharges while charging when I am playing like NFS most wanted.
Sent from my Nexus 4 using xda app-developers app

The issue with cables is with the LG usb wall charger as the one supplied isn't capable of getting the 5 volts at 1.2 amps that the charger is rated at, mine is getting around 300 - 400 mA. The micro usb cable I have in my car and use with my laptop (for charging and data transfer) is able to handle the higher amperage, it gets around 1 amp with the LG plug. There are no specs on these cables so I can't list a definitive difference and I would assume that the cable mod in the OP might help with the LG cable. It also might just be simpler to only buy those cables capable of handling higher amperage as obviously they are out there from my experience.

The cable I'm using is an RCA coiled charging/syncing cable model AH732CBR (has data pins). The maximum I'm getting from this is about 870 mA regardless of the amperage of the usb port, I've tried a 1.0, 1.2 and 2.1 and they are all around 870 mA on current widget. I would suppose if I could find a strictly charging cable I could get higher (link to ebay in OP is outdated) but this is still 2x that which I'm getting from the LG cable supplied with the phone which only puts out 300-400 mA. Our phone also has Qualcomm's quick charge which is supposed to improve battery charging times by 40%.
http://www.droid-life.com/2013/02/1...allows-your-device-to-charge-up-to-40-faster/

How do you measure how much mA the device draw from the charger?
Sent from my Nexus 4 using Tapatalk 2

omrij said:
How do you measure how much mA the device draw from the charger?
Sent from my Nexus 4 using Tapatalk 2
Click to expand...
Click to collapse
current widget, link is in the OP

kzoodroid said:
The cable I'm using is an RCA coiled charging/syncing cable model AH732CBR (has data pins). The maximum I'm getting from this is about 870 mA regardless of the amperage of the usb port, I've tried a 1.0, 1.2 and 2.1 and they are all around 870 mA on current widget. I would suppose if I could find a strictly charging cable I could get higher (link to ebay in OP is outdated) but this is still 2x that which I'm getting from the LG cable supplied with the phone which only puts out 300-400 mA. Our phone also has Qualcomm's quick charge which is supposed to improve battery charging times by 40%.
http://www.droid-life.com/2013/02/1...allows-your-device-to-charge-up-to-40-faster/
Click to expand...
Click to collapse
Bit of a late reply but please bear in mind the Nexus will NOT draw anything more than about 800mAh from the wall for charging alone. That is the absolute max and is a hardware limit - If the cable is transmitting that and it's showing in current widget you've got a good setup. See the added section in OP for more info on higher amperage chargers.