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Alternative 5V chargers (currency?)

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.
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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.
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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 ?
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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.....
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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?
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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.

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.
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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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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
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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.
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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
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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.
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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
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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)
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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.

Technical details about nook HD+ charging

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.
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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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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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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.
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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.
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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.
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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.
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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.
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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
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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.
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Just wondering how do you charge the battery externally?

invinciblemo said:
Just wondering how do you charge the battery externally?
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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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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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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.
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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.

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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.
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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?
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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.

Issue when connected to computer! Help!

Yesterday I've received my Tab S2 8.0". After the first charge I connected the tablet to my computer to upload some files and I get a red "X" on the battery and the message: "Slow charger connected"
In the notification area I get a constant red "Device charging slowly. To charge faster, use the original charger".
Is this normal? Cause I'm using the USB cable that came with the device and tried with USB3.0 and USB2.0 with the same results.
Oh, extra info! The tablet was bought in France, I'm from Argentina.

XinsaX said:
Yesterday I've received my Tab S2 8.0". After the first charge I connected the tablet to my computer to upload some files and I get a red "X" on the battery and the message: "Slow charger connected"
In the notification area I get a constant red "Device charging slowly. To charge faster, use the original charger".
Is this normal? Cause I'm using the USB cable that came with the device and tried with USB3.0 and USB2.0 with the same results.
Oh, extra info! The tablet was bought in France, I'm from Argentina.
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Click to collapse
Yes it's normal.
USB ports cannot put out as much current as a decent charger (like the one the tablet came with). Hence it charges more slowly using USB (or indeed some inferior or lower powered plug-in chargers), and it's warning you that it is doing so. I think the maximum a USB2 port can provide is about 500mA, with USB3 about 900mA or so.
Compare that to the proper plug-in charger, which is 2A (if I remember correctly).
Some motherboards etc do have higher current USB ports for charging etc, but that's non-standard and they are usually specially labelled as such.

Oh, thanks for the help. I got a little scare with the warning.

I got the same tablet, and also noticed this warning about battery charing slowly, and asking me to use original charger.
It's working resonably ok with original charger, though it charges slow with other chargers with the same AMP rating. E.g. it charges slowly with the larger iPad charger, which is also 2 AMP rated ...
Charing with iPad charger is so slow, that when I use the device with during charging, it drains faster than it charges! Quick unusual ...
Anyone? Any comments?

Theres an excellent app called Ampere which gives you info on the tablets charging and power consumption - useful and interesting.
Cant post links yet so just search for it on Play

Also don't forget that (when not built-into the charger) the cable is also important to the amount of current reaching the tablet.
The best charger in the world may well struggle if a long cable with hair-thin high resistance wiring is used to transfer the power into the tablet.
Lastly even though many chargers are labelled as 5v 2A, they may not actually be able to provide that under load, and if things drop when a hungry device like a tablet is connected then things will slow up.
I have a few 5v 2A chargers which come up as slow charging, whereas others which were more purposefully designed (e.g. the 5v 2A charger from my old Nexus 7) work just as well as the supplied Samsung one.

DarrenHill said:
Also don't forget that (when not built-into the charger) the cable is also important to the amount of current reaching the tablet.
The best charger in the world may well struggle if a long cable with hair-thin high resistance wiring is used to transfer the power into the tablet.
Lastly even though many chargers are labelled as 5v 2A, they may not actually be able to provide that under load, and if things drop when a hungry device like a tablet is connected then things will slow up.
I have a few 5v 2A chargers which come up as slow charging, whereas others which were more purposefully designed (e.g. the 5v 2A charger from my old Nexus 7) work just as well as the supplied Samsung one.
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this is such onfortunate ongoing issue
i got my Tab S2 - SM-T715Y in Thailand as i am backpacking Asia ..
I know the warranty is per country .. so I can not use it where I am now - in Vietnam .. or back home in USA
I realized that this was a major factor before buying .. so I can go through my credit cards extended warranty ..
in the future I will buy Acer or Asus or alike that have international warranty ..
yesterday I was on a road trip
and I was using my 12V car charger
and then a battery bank .. and I think it rigered this problem or fact that I drained my S2 to 0%
fact is that now it is showing "slow charger connected" .. I am using the original charger and cable
now it is slowly *discharging* when connected to AC!!
also will try to whipe the cache..
this is so terrible
I am losing faith in Samsung :/ (had charging issues with my Note 3 .. 8 months in .. motherboard issue)
I can not find a solution to this problem
I am thinking of putting it in a refrigirator? maybe it will do something to the battery?

Note 9 Charges Faster When Fast Charge Is Disabled

I've been having a repeatable problem. I have a Note 9 that will charge faster when I disable fast charging under battery settings. I tested the load being drawn with a USB Power meter these are the results I got.
Using a USB-A to USB-C cable:
When QC is enabled:
Phone draws 0.5amp charge, 10ohms resistance at 5.02V.
When QC is disabled:
Phone draws 1.2 amps, 3.9 ohms resistance, at 5.02V
I am using the same cable, same power bank. The power bank's USB-A port is able to draw ~1.9 amps at 5V, tested using a USB Meter and Load Tester that will put the USB under 1 amp and 2 amp loads at 5V, with resistance being ~2.7 ohms without the power bank turning off. I haven't tested the power bank at 9V, I don't have a 9V load tester
When I immediately switch from QC to non QC, the results above are repeatable.
Things I Have Done So Far:
Reboot Phone
Clear Phone Cache
Reboot Into Safe Mode
Try Different Charging Cables, Blocks, including OEM parts.
Every once in a while, it will switch back to being able to QC fast charge but it is random.
If I use a Power delivery capable block charger, it will charge at ~2750mA (I dont have other numbers like amps, voltage, or resistance, I'm still waiting on a USB-C meter)
My phone's wireless charging has no problem operating at it's max capacity
Any one else have this problem? Anything else I could do before I factory reset my phone?

I posted about losing Fast Charge thru the stock cable a while back and got no answers or a fix. I have not tried turning off the option to see if it charges any faster. It takes almost 2 to 3hrs to fully charge at this point. I'll take any fix or work around at this point.

TokedUp said:
I posted about losing Fast Charge thru the stock cable a while back and got no answers or a fix. I have not tried turning off the option to see if it charges any faster. It takes almost 2 to 3hrs to fully charge at this point. I'll take any fix or work around at this point.
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Turning off fast charge made my charging a bit better. With Fast Charge (FC) turned on, I was getting 0.5amps (gave around 400-500mA). Turning FC off, sped up my charging by 50%, charging at 1.2 amp (roughly gave me 800-1000mA; Both charges were at 5V). Im able to charge at around 1000 mA with this setup, a little less than wireless quick charge. No idea why turning it off helped.
Another workaround that brought my charging speed WAY UP, to 2500mA, was buying a Power Delivery (PD) capable block WITH A USB-C to USB-C cable. I can get normal fast charging speeds with that setup.
I cant get FC with USB-A to USB-C cables, which is frustrating as most of my charging blocks are the regular USB-A input port.
Hope this helps you. 2-3 hour charge is brutal.

What's even weirder is in my car my phone would barely charge. But since I lost FC at home, it started working in the car. So in my car I can FC but not at home. I even tried the wire I use in the car and still nothing. Idk what is going on

Is it possible that turning off QC is turning off a regulation in the software to keep the battery from overheating? With this regulation turned off that would normally be on when quickcharging, the regulation is not active, thus causing the battery to charge at a less regulated speed, causing charging to be faster? Maybe there's a QC bug currently that's hampering it's full potential? What software version are you guys currently?
I just checked QC on mine on the latest Xfinity version and no matter what charger or cable I use with the function, it is working.

It's def not a software thing. I'm on latest October patch. Samsung told me that they have seen some issue with the charging port and once it goes bad there is nothing to do but replace it. They told me to bring it in to a store for repair thru my carrier. Haven't had a chance to go.

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Jammol said:
Is it possible that turning off QC is turning off a regulation in the software to keep the battery from overheating? With this regulation turned off that would normally be on when quickcharging, the regulation is not active, thus causing the battery to charge at a less regulated speed, causing charging to be faster? Maybe there's a QC bug currently that's hampering it's full potential? What software version are you guys currently?
I just checked QC on mine on the latest Xfinity version and no matter what charger or cable I use with the function, it is working.
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Click to collapse
That what I was thinking. Something is actively limiting the charge coming in. Everytime I had quick charge enabled I've been monitoring the ohms and the resistance would automatically jump to 10ohms. Then I disable QC and the resistance automatically drops to around 6 ohms.
I'm running Android Pie 9.0, Kernel version 4.9.112

TokedUp said:
It's def not a software thing. I'm on latest October patch. Samsung told me that they have seen some issue with the charging port and once it goes bad there is nothing to do but replace it. They told me to bring it in to a store for repair thru my carrier. Haven't had a chance to go.
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Nocturncal said:
That what I was thinking. Something is actively limiting the charge coming in. Everytime I had quick charge enabled I've been monitoring the ohms and the resistance would automatically jump to 10ohms. Then I disable QC and the resistance automatically drops to around 6 ohms.
I'm running Android Pie 9.0, Kernel version 4.9.112
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Yeah it could definitely be hardware related as well, due to each pin on a type c charging serving different purposes. There are two specific pins(I think it's two), that are responsible for enabling higher input of electricity. Couple years ago Google made comments about the cheap Amazon knock off cables and why they failed after a short while. Wouldn't surprise me if Samsung cheaped up for the cables and port on the device. I'll have to try and find the articles I read concerning the pins.
Here's a good start to understanding Type C.
https://www.allaboutcircuits.com/te...pe-c-which-pins-power-delivery-data-transfer/

Its the **** cable they supply with the phone.
I had all the same problems.
I noticed that when I turn off quick charge the phone can charge at 5v 1.7 amps. (USB doctor).
When I turn on quick charge it can only charge at 5 volts 0.40 amps.
The phone is trying to charge at 9 volts but for some reason cant so it goes into this safe mode.
I purchased a new Samsung cable it lasted for a week and developed the same problem.
A hint when it develops this problem Dex stops working.
I tried all kinds of cables. One Plus 5, and a few others. I finally got it to work again with my wifes one plus 6 cable.
Im now researching USB Type C ports and USB standard 2, 3, 3.1, 3.2
As well the quick charge tech used by Samsung. Its not Quick Charge 2. Its a proprietary standard.
So if your having problems with quick charge it could be due to your cable or your Port. Things very rarely go wrong with the charger. Also get yourself a USB Doctor. Its a big help. And only costs a few bucks.
Hope this helps somebody out there.
Right now I am trying to compare Note 9 vs Note 20 USB cable.