As an engineer I pulled some info from the datasheet for the chip the nook uses, it may help better understand charging issues.
full datasheet is on the TI site at:http://www.ti.com/lit/ds/symlink/bq24196.pdf
USB Timer when Charging from USB100mA Source
The total charging time in default mode from USB100mA source is limited by a 45-min max timer.
Click to expand...
Click to collapse
If you connect the nook to a low power pc port you will only be able to run the charging for 45 minutes before the charger IC stops. To start it again you have to unplug and re-plug the USB cable. The charge current for a 500ma usb port is about 440ma.
The device initiates and completes a charging cycle without software control. It automatically detects the battery
voltage and charges the battery in three phases: pre-conditioning, constant current and constant voltage. At the
end of the charging cycle, the charger automatically terminates when the charge current is below a preset limit in
the constant voltage phase. When the full battery falls below the recharge threshold, the charger will
automatically start another charging cycle.
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Click to collapse
The device fast charges at 1.5A using the charger and charges at 4.208V to the battery. The bad battery setting is for 1.8V, so if your device battery falls to that level it will not charge because the chip assumes a failed battery. I see this a lot in tablets. Someone stops using the tablet when the charge is 10% or less and then 2 weeks later picks up the tablet and it appears dead. The battery cells have discharged below the limit and now will not charge. The device will consume power even if you power off the device because the charging controller is on 24/7 regardless of any mode except shipping mode which we do not have access to . Fix for dead battery is remove the battery from the tablet, charge on external charger , replace.
The USB ports on personal computers are convenient charging source for portable devices (PDs). If the portable
device is attached to a USB host, the USB specification requires the portable device to draw limited current
(100mA/500mA in USB 2.0, and 150mA/900mA in USB 3.0). If the portable device is attached to a charging port,
it is allowed to draw up to 1.5A
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Click to collapse
if you want the info on your own charge stats just type dmesg in a shell prompt.
data to look for is like this:
Code:
<7>[224884.880706] bq2419x_is_vbat_in_range: vbat = 4135000
<7>[224884.881378] bq24196 1-006b: bqSetSYSMIN: 3200
<7>[224884.882019] bq24196 1-006b: adj_fast_ichg_lim: 2036, 240, 2036
<6>[224904.594329] android_usb gadget: high speed config #1: android
<7>[224904.594818] bq24196 1-006b: USB_EVENT_ENUMERATED
<6>[224904.595306] android_work: sent uevent USB_STATE=CONFIGURED
<7>[224904.600708] bq24196 1-006b: INTERRUPT 08=6c, 09=0
<7>[224904.600952] bq24196 1-006b: S: Power Good
<7>[224904.601165] bq24196 1-006b: S: CHARGE STATE = 2 (FAST CHARGING)
<7>[224904.601531] bq24196 1-006b: S: VBUS STATE = 1 (USB host)
<7>[224904.601745] bq24196 1-006b: S: Dynamic Power Management enabled
I have had a few close calls with my battery. It does not charge if verygreen's or other app that permits the Nook to host other USB devices is active, and in most cases I had accidentally activated it. Since it then refuses to charge when connected to power, its in greater danger of completely depleting. Easily fixed as long as the unit is still operating, but no obvious clue when that's the problem.
Also, when you put the power plug in real slow at the nook port, even when the battery is not 100%, it will turn green as if full charged and will no longer show that its charging. Possibly, could be initiated in another way I would think.
modelworks said:
If you connect the nook to a low power pc port you will only be able to run the charging for 45 minutes before the charger IC stops. To start it again you have to unplug and re-plug the USB cable. The charge current for a 500ma usb port is about 440ma.
Click to expand...
Click to collapse
Interesting about the "low power" port. But I haven't seen one yet. Nowadays, many USB2 ports provide up to 1000 mA without negotiation. Originally, the USB specification required that devices connect in a low-power mode (100 mA maximum) and communicate their current requirements to the host, which then permits the device to switch into high-power mode. But the USB Battery Charging Specification changed that. In recent years I've tested several PC mainboards, and an Xbox 360, all of them provide around 1000 mA on USB2 ports without negotiation.
But the Nook HD+ won't make use of that and limit itself to the 440 mA you mentioned. Why? Because it uses the two data lines (D+ and D-) of the USB connection to detect dedicated USB chargers. If the data lines are shorted, the Nook assumes it's connected to a dedicated USB charger and it will draw up to 2000 mA (about 1880 mA in my measurements). If the data lines aren't shorted, it'll limit to 440 mA no matter if the USB power source could provide more.
modelworks said:
The device fast charges at 1.5A using the charger and charges at 4.208V to the battery.
Click to expand...
Click to collapse
From where do you get the 1.5 A? Your own dmesg output says "adj_fast_ichg_lim: 2036, 240, 2036", and as I said, mine charges with around 1.8 A.
Also, the line in the dmesg output that gives away the charging speed isn't "CHARGE STATE". It always reads "= 2 (FAST CHARGING)" when an external power source is connected.
The line "DCP detected" is the real confirmation (DCP = dedicated charging port), and apparently also "VBUS STATE".
"VBUS STATE = 1 (USB host)" means the data lines are NOT shorted => max. current intake is 440 mA
"VBUS STATE = 2 (Adapter port)" means the data lines ARE shorted => max current intake is ~2 A.
Furthermore, keep in mind that power from the external source is prioritized to first supply the system, and then the battery. That is, the battery is charged with the "leftovers". Therefore, if you connect the Nook to a source from which it'll only draw the mentioned 440 mA, and you're continuing to use the tablet, then it can happen that the battery won't be charged, or even will be discharged! If you perform some CPU/GPU intensive tasks on the tablet, its power consumption can easily exceed 440 mA, meaning the tablet will use the external source in combination with the battery to satisfy its hunger.
TL;DR:
Nooks will only fast charge on dedicated charging ports, which are recognized by having their data pins shorted. That's more or less standard nowadays for generic USB chargers (USB Battery Charging Specification). However, some chargers still don't meet this requirement, and Apple has their own incompatible standard, naturally.
Don't use your tablet if you want to charge it from a low-power source (i.e. USB data connection on the Nook), because depending on the workload, the battery will be charged very slowly or will actually be discharged.
Tzul said:
Interesting about the "low power" port. But I haven't seen one yet.
Nowadays, many USB2 ports provide up to 1000 mA without negotiation. Originally, the USB specification required that devices connect in a low-power mode (100 mA maximum) and communicate their current requirements to the host, which then permits the device to switch into high-power mode. But the USB Battery Charging Specification changed that. In recent years I've tested several PC mainboards, and an Xbox 360, all of them provide around 1000 mA on USB2 ports without negotiation.
Click to expand...
Click to collapse
Read page 19 of the document.
From where do you get the 1.5 A? Your own dmesg output says "adj_fast_ichg_lim: 2036, 240, 2036", and as I said, mine charges with around 1.8 A.
Click to expand...
Click to collapse
I just posted that for people to know the general section not as a specific example.
Page 28 of the document explains why the log may read 2036 but actually be 1.5A
modelworks said:
Read page 19 of the document.
Click to expand...
Click to collapse
Have you read it? It's talking about the USB standard there rather than the bq24196. "If the portable device is attached to a charging port, it is allowed to draw up to 1.5A". That's straight from the USB standard, as the common USB2 connectors are rated for up to 1.5 A. However, B&N have engineered their own proprietary cable and connector and provide a 2 A capable power supply, so that limit doesn't apply.
Also, see Table 2 on the same page. The automatic input current limits are 100 mA, 500 mA, and 3 A. Not 1.5 A.
modelworks said:
I just posted that for people to know the general section not as a specific example.
Page 28 of the document explains why the log may read 2036 but actually be 1.5A
Click to expand...
Click to collapse
It would be interesting to open a Nook and take a look what resistor value they used for that safety setting, if they used one at all. As I said before, I've measured currents up to 1.88 A on my Nook HD+ from the official charger, so I seriously doubt they hardwired it to 1.5 A max (and wasted money by providing a 2 A power supply when a 1.5 A one would suffice).
PS: Do you know the power supply dir in the Linux SysFS? Check out /sys/class/power_supply/ and its subfolders (one for each power source). There you can find various virtual files, part of which contain monitoring values straight from the hardware, as read by the driver.
In /sys/class/power_supply/bq27500-0/current_now (or in the file "uevent" which contains a summary of the individual values) you can read the battery charge/discharge current, as measured by the PMU chip. I saw values above 1.7 A there last time I charged and checked. And in order to check, I had to wake up the tablet from standby, of course, meaning that some of the power was spent on running the system rather than charging the battery... All of this paints a pretty clear picture: the device really does fast charge at about 2 A (if you use a suitable power supply and if you let the tablet sleep while charging). Not 1.5 A.
modelworks said:
The device fast charges at 1.5A using the charger and charges at 4.208V to the battery. The bad battery setting is for 1.8V, so if your device battery falls to that level it will not charge because the chip assumes a failed battery. I see this a lot in tablets. Someone stops using the tablet when the charge is 10% or less and then 2 weeks later picks up the tablet and it appears dead. The battery cells have discharged below the limit and now will not charge. The device will consume power even if you power off the device because the charging controller is on 24/7 regardless of any mode except shipping mode which we do not have access to . Fix for dead battery is remove the battery from the tablet, charge on external charger , replace.
Click to expand...
Click to collapse
Just wondering how do you charge the battery externally?
invinciblemo said:
Just wondering how do you charge the battery externally?
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Click to collapse
By opening the tablet, removing the battery, and connecting it to a dedicated Li-ion charger, of course. Something like this - but that's just an example, that model would not work. You'd probably have to do some soldering for the connector, too.
Tzul said:
By opening the tablet, removing the battery, and connecting it to a dedicated Li-ion charger, of course. Something like this - but that's just an example, that model would not work. You'd probably have to do some soldering for the connector, too.
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Click to collapse
I tried finding online to see if anyone had tried charging the battery externally.
It seems that dormouse1, from the second post in this thread http://4pda.to/forum/index.php?showtopic=431820&st=1900, had tried charging it using Imax B6.
I'm going to try charging my battery using his setup and see if it works.
To anyone that is interested in charging their battery externally, i think a TP4056 a Lipo Battery Charging Board works.
I had managed to charge my battery, and it shows that it has a discharge voltage of 4V, but I am not sure if it is correct.
When my charged battery is connected to my tablet, the battery discharged and my tablet became hotter.
However, my tablet failed to boot.
So its either that my tablet is bricked, or the charger did not charge my battery properly.
I would like to ask does anyone knows, what is the voltage of a fully charged battery?
invinciblemo said:
I would like to ask does anyone knows, what is the voltage of a fully charged battery?
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Click to collapse
Lithium-ion cells are typically charged to 4.20V. The Nook HD+ uses that value, too. Nominal voltage is 3.7V. I forgot the cut-off voltage that the HD+ uses to decide that the battery is empty, but I think it was 3.4V or 3.5V.
Tzul said:
Lithium-ion cells are typically charged to 4.20V. The Nook HD+ uses that value, too. Nominal voltage is 3.7V. I forgot the cut-off voltage that the HD+ uses to decide that the battery is empty, but I think it was 3.4V or 3.5V.
Click to expand...
Click to collapse
To add to that, make sure you put a load on the battery if you are measuring the voltage of the battery disconnected.
Something like a single 330 ohm resistor would be good.
Bad lithium batteries sometimes will appear charged until you place the load on it then it falls to 2 or lower volts.
Another quick check is to make sure the battery casing is completely flat, if the battery has bulges of more than a few millimeters the battery is about to fail and should be discarded immediately. Another trick you can use is smell the battery, I know sounds weird , but failing lithium batteries have a very unique odor , almost sweet, reminds me of the smell of bananas.
HTML:
Tzul said:
[*]Nooks will only fast charge on dedicated charging ports, which are recognized by having their data pins shorted. That's more or less standard nowadays for generic USB chargers (USB Battery Charging Specification). However, some chargers still don't meet this requirement, and Apple has their own incompatible standard, naturally.
[*]Don't use your tablet if you want to charge it from a low-power source (i.e. USB data connection on the Nook), because depending on the workload, the battery will be charged very slowly or will actually be discharged.
Click to expand...
Click to collapse
I have an HD+, which I have not been able to get to charge on a 3amp, 2amp or even a 1amp wallwart, but it does charge via its Nook wallwart. Does the above mean that were I to 'repurpose' a short USB extension and simply short the D- and D+ (clear of the +ve and ground) together in the USB lead, that I should then find it will charge via that lead? Please?
harrym1byt said:
Does the above mean that were I to 'repurpose' a short USB extension and simply short the D- and D+ (clear of the +ve and ground) together in the USB lead, that I should then find it will charge via that lead? Please?
Click to expand...
Click to collapse
Sorry for the late response.
Yes, that is correct, I have built such a cable myself and it does work.
Battery Issues
I have a Nook HD and it immediately dies as soon as it is unplugged, however there is no apparent damage to the battery, no bulges, leaks, or smells. After I plug it in and it reboots it goes from 10-20% charge to 100% charge within minutes. Is there a way other than removing the battery and charging it externally (outiside of my mechanical ability) to reset the battery to determine if it is a software issue or an issue with the battery itself. Currently running CM 10.2.1 stable.
Charging problem - solved
I had similar symptoms with my Nook HD+ : when plugged into charger the indicator light turned green, then orange, but only for a second, then went dark. When left on charger for many hours, the indicator would start blinking red. Nothing worked, until I read technical details in this thread.
The bottom line: if the battery voltage drops below 1.8 V, the stupid control chip assumes the battery is "bad" and refuses to pass the charging current; consistent with the observed symptoms. This gave me an idea on how to fix this:
Step 1: Open the Nook by prying the front panel to get access to mounting screws, then unscrew the back panel.
Step 2: Locate the battery cable composed of three red, three black, one blue, and one yellow wires.
Step 3: Locate the gold test points on circuit board _under_ the wires: "VBAT" under the red wires, "BAT-" under the black wires.
Step 4: You have to trick the control chip into "thinking" that the battery is still "good". For this, you'll need an external voltage source. I used my homemade adjustable DC power supply setting it to 2.5 V. I guess, any voltage between 1.8 - 3.7 should work.
Step 5: Connect the _positive_ lead from the external power source to the "VBAT" test point, connect _negative_ (or ground) lead to the "BAT-" test point.
Step 6: Plug your Nook into charger and wait a few seconds: the indicator light will now stay solid orange meaning the charging current is passing through. Yay! You should disconnect the external DC source; it's no longer needed.
I can confirm that applying voltage to the test points does absolutely nothing. In examining the PCB the test points mirror the positive and negative connections of payload from the battery.
That is NOT how the charging chip works. There are 2 control lines tied internally to the LiPo battery which are NOT payload lines. That is what we need to play with but there's no information on how those control lines are tied into the cell's internal chemistry or what the expected levels might be for the chip to "think" that the battery is good. It could even be an interface, i2c or who knows
I guess I am in trouble then...
I found my Nook HD+ back after not having used it in 3 years. Battery is dead as a door nail. When I plugged it in though, it showed the battery symbol for a dead battery and then the amber light next to the cable connector lit up and is still lit 30 minutes later. I am going to let it charge overnight and hope that it works again. If not, I don't think I will bother with pulling the battery, etc.
Related
Hi, I'm really a noob when it comes to electronics. For all I know, when a cable fits it should work
I have a couple of microUSB chargers laying around. They all have an output of 5 Volt but they output a currency that differs from the standard charger (1A).
What is the "golden rule" wrt currency? Are chargers with a currency that is less than 1A save?
current is not pushed, it is pulled by your device as necessary. voltage is pushed, so correct voltage,5V in this case, is very important. As for the current, if the charger can't supply enough current with that voltage it will get hot and cause problems. i.e., you should have a current greater or equal to your original charger and same voltage. this applies to ALL of your electronics.
ozkaya said:
current is not pushed, it is pulled by your device as necessary. voltage is pushed, so correct voltage,5V in this case, is very important. As for the current, if the charger can't supply enough current with that voltage it will get hot and cause problems. i.e., you should have a current greater or equal to your original charger and same voltage. this applies to ALL of your electronics.
Click to expand...
Click to collapse
Thank you very much for this explanation. What do you think, a 5v charger with a current of 850mA will that cause big problems when I use it just accidentally to charge my device.
appelflap said:
Thank you very much for this explanation. What do you think, a 5v charger with a current of 850mA will that cause big problems when I use it just accidentally to charge my device.
Click to expand...
Click to collapse
It probably wouldn't be a lot of problems, if you really have to do it, charge it when the screen is turned off, so that you will need less current.
You can charge without risk with any USB charger. Unless the charger "signals" that it can supply more than 500mA by having the 2 USB data pins shorted, the HD2 won't pull more than 500mA, which is the minimum a USB charger must be able to supply.
"Golden rule" - If You have 5V its safe for Your phone, current level is determining the time that You need to charge battery.
Kilrah sad that HD2 'pull' no more than 500 mA - ok, if this is true ( i believe it is , he always make some test for it ) original charger needs about 2h, with 250 mA charger it will take more than twice of that time - 4h ( it's not fully linear )
@Kilrah - did You test what's power ( current taken ) consumption during charging ? it's really only 500 mA ? if so, than why HTC use 1A charger ? usually safety rules are about 15 - 30% more than max current needed.
0.5 A + 30% = 0.65A , so why 1A ?
The minimum current what HD2 accepts is 500mA because this is the USB standart.
If the supply could deliver more than 500mA the HD2 will take it up to 1000mA. The maximum current which the HD2 can use is 1A (1000mA).
So if your charger can deliver 5V and 2000mA the HD2 will limit the current to 1000mA. So you can use a charger, when the voltage is 5V and the current at least 500mA.
The push pull principe in the post before is correct, because the charger is a voltage source and not a current source.
I am already enjoying the benefits of proposed standardisation of phone chargers to micro usb pin. Since I upgraded with HD2 from Nokia N97 I am using the nokia wall chargers as well as well as car charger. I didnt have to buy new charging accessories for this mighty HD2.
By the way would the Nokia data cables (micro usb) be able to sync data when used with HD2. Havent tried yet.....
afropolak said:
@Kilrah - did You test what's power ( current taken ) consumption during charging ? it's really only 500 mA ? if so, than why HTC use 1A charger ?
Click to expand...
Click to collapse
As said, IF the 2 USB data pins are NOT shorted (that's how it is by default on <500mA/3rd party chargers, or on a PC), the HD2 will limit the current it pulls to ~450mA.
IF they are shorted (on chargers that support higher current like the supplied one) the HD2 will pull more. With the supplied charger it's about 850mA, with a 3rd party "800mA" Chinese charger that didn't have the pins shorted but was modded to have it done, it pulls about 650mA.
PlayStation said:
By the way would the Nokia data cables (micro usb) be able to sync data when used with HD2. Havent tried yet.....
Click to expand...
Click to collapse
Micro USB is a standard, so every micro USB cable should be the same. If not, you've got a botched knockoff.
so how do you short the cable assuming I get a car charger without a USB to micro USB cable and sourced my own cable from a parts bin that was probably for computer usage?
cheahcl said:
so how do you short the cable assuming I get a car charger without a USB to micro USB cable and sourced my own cable from a parts bin that was probably for computer usage?
Click to expand...
Click to collapse
I don't think that would be a good move!
You would have to be certain of the regulation circuitry of the charger and it's ability to cope with the attendant initial draw of the battery when plugged in.
This will depend on the state of drain of the battery and the various functions in operation at the time on the phone.
At the moment of plugging in is when the draw will be highest and when any protection circuitry will be essential.
A well topped up battery will "draw" less than a depleted one and will continue charging on as little as 350mAh (again depending on what is running on the phone).
A very depleted battery may well not even start the charging process at such a level. That's why the HD2 comes with a 1000mAh wall charger!
The levels quoted for PC/Laptop USB power are nominal off load levels and will vary depending on any othe devices plugged in on the same bus supply.
So, with a PC that has a few attached USB devices, you may well NOT see 500mAh and as has been reported before, you can get battery depletion back into the USB port as other devices draw from the phone!
Always best to keep the battery topped up to prevent "charging strain" on the cells. This will maximise the capacity available when you need it for those longer periods of time.
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?
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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.
Quick question. If you leave your phone plugged in and its fully charged and your using it, is the phone just leeching off the charger for power or is the charger pushing out small bursts of power to the battery. The context of my question is i'm starting to use webtop alot and I leave my phone on all day plugged in. Is continuing this behavior going to impact my battery or does the phone just leech directly off the charger without using the battery?
It's fine to leave it plugged in all the time. The phone has a "smart circuit" that use what is called trickle charge to just continually top off the battery as it drops below full charge. The phone is designed such that it doesn't receive power directly from the charger or USB cable, unless the +5v DC current is on pin 1 like a factory flash cable.
Bottom line is there is no damage or shortening of the life of the battery to leave it charging all the time while in the dock or any other means and Li Ion batteries no not have memory problems.
On a related note, is there any damage in using low-power chargers?
I have an external solar-powered battery charger that also supports USB-out, and I find that it doesn't put out enough power to really charge the battery, but it can keep the battery at its current charge level (whenever it is plugged in) for the equivalent of one charge (so the phone could theoretically last 2ish days).
I'm wondering whether this is constantly charging/discharging the battery (bad thing), or just providing enough power to run the phone (good thing).
I've also seen a similar behavior when charging over USB. If I'm using the phone a lot, sometimes a usb port doesn't supply enough juice to charge the phone.
I also saw this in some (rarer) cases with my OG Droid, but I didn't pay it much mind because I had 3 batteries for that thing and you could pick them up for a few dollars off of Amazon.com.
Thanks!
cellzealot said:
It's fine to leave it plugged in all the time. The phone has a "smart circuit" that use what is called trickle charge to just continually top off the battery as it drops below full charge. The phone is designed such that it doesn't receive power directly from the charger or USB cable, unless the +5v DC current is on pin 1 like a factory flash cable.
Bottom line is there is no damage or shortening of the life of the battery to leave it charging all the time while in the dock or any other means and Li Ion batteries no not have memory problems.
Click to expand...
Click to collapse
Thank you so much for your response. I had a feeling it was something like this. Good old "smart circuit".
podspi said:
On a related note, is there any damage in using low-power chargers?
I have an external solar-powered battery charger that also supports USB-out, and I find that it doesn't put out enough power to really charge the battery, but it can keep the battery at its current charge level (whenever it is plugged in) for the equivalent of one charge (so the phone could theoretically last 2ish days).
I'm wondering whether this is constantly charging/discharging the battery (bad thing), or just providing enough power to run the phone (good thing).
I've also seen a similar behavior when charging over USB. If I'm using the phone a lot, sometimes a usb port doesn't supply enough juice to charge the phone.
I also saw this in some (rarer) cases with my OG Droid, but I didn't pay it much mind because I had 3 batteries for that thing and you could pick them up for a few dollars off of Amazon.com.
Click to expand...
Click to collapse
To my knowledge, there is no reason a low power charger should present any problem, but charging from the USB on a PC is limited to 350mA and will definitely not push enough current to charge the phone while it is under heavy use like Mobile Hotspot tethering with LTE or even 3g.
The standard wall charger is 850mA and even that can sometimes only keep up or charge very slowly under heavy load.
USB spec is [email protected] not 350mA. But yes, a dedicated charger probably will charge faster. Some may go as high as 1A output...
Sent from my DROID4 using Tapatalk
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
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.