[Q] Faster USB Charging? - Nexus S Accessories

Just reading up on USB chargers, and I found somewhere in a thread here about phones defaulting to smaller ma when charging via USB if the connector didn't have the data pins shorted or something.
So, I was wondering a couple of things:
1) If the default charger supplies 700ma, do you think that is the most the Nexus S can draw? Does anyone have one of these shorted USB chargers? Does it charge the NS faster?
2) If it does charge faster, how hard would it be to do something similar to shorting the data connections? I have a generic AC-USB cable which I currently use for my iPod touch.
3) Is there a way to check if it is already shorted out? The USB charging port looks similar to ones on my computer, but I'm not sure what to look for.
Thanks for any help! Maybe if we can sort out this stuff, we can provide a solution for those looking for faster charging!

it does work safely, i'm using a 1000 mAh charger at home, and a 2000 mAh charger in the car both are from aftermarket eBay/DealExtreme charges.
no overheating
and charges faster than stock

AllGamer said:
it does work safely, i'm using a 1000 mAh charger at home, and a 2000 mAh charger in the car both are from aftermarket eBay/DealExtreme charges.
no overheating
and charges faster than stock
Click to expand...
Click to collapse
Ok thankyou for that AllGamer, I'll think of possible ways I could mod the charger now

The only reason it is slow is because of the USB charging brick instead of just a charger.
Sent from my Nexus S using XDA App

I know it's a wrong thread, but anyone has any pointers as to how to short a regular USB cable to make the phone think it's a power adapter cable?

XBOHDPuKC said:
I know it's a wrong thread, but anyone has any pointers as to how to short a regular USB cable to make the phone think it's a power adapter cable?
Click to expand...
Click to collapse
Nah it's not the wrong thread that was one of my questions! I'm not sure exactly where you would do it, but maybe if you skinned the wire, then cut the data lines it would work?
Not sure which end you would do it on however, but that may not matter. Any other ideas?

The two center pins in the USB carry the data. If you pull them out, the cable won't be able to connect to the computer.
Sent from my Nexus S

Wow - you don't need to do this and you wouldn't want to in a computer anyway.
The USB specification says that 500ma (@ 5v) of current should be available from a computer's USB port. Of course, the actual wires can carry much more than this, so manufacturers can tell their phones to takes as much current as is offered.
Almost all computers limit their USB power output accordingly - this is why some opld usb-powered external hard drives needed 2 USB plugs to get enough power. The only computers that I am SURE emit significantly more than 500ma on their USB ports are first and second generation MacBook Airs.
Some phones, the N1 and every other HTC specifically, look for a specially shorted cable to "know if they are plugged into the wall adaptor" as opposed to a computer USB port. In reality, this is just a way to make you specifically buy HTC chargers as opposed to third-party off-brands, because plugging one of these phones into an off brand charger will limit the current draw to about 450ma.
If you want to know if your Android phone thinks that it is in "USB" mode or in "AC" mode, just plug the phone in, open the dialer, enter *#*#4636#*#* and then select battery info. If your phone is one that cares (not all do), it will say USB if it thinks it should be in USB charging mode, or AC if it thinks it should be in AC charging mode.
I would not try shorting out the middle pins in a cable and then plugging it into the computer. First, most will probably just disable the USB port completely, shutting off even power you could draw. Second, if it doesn't shut down, you run the risk that a badly-built USB port might not properly limit the current to 500ma - and since they are not designed to furnish more current than that, you might melt something expensive or start a fire. third, if you make a mistake, you risk shorting out either your phone or your computer, which might ruin your day, week or month, depending on your financial means to replace the system that cooks itself.
I would just run out to your local store, pay 15 bucks for a 2A third-party usb charger brick, and go to town. That will work perfectly - this is what I use, and it probably cuts the charge time by 30-40%. Obviously, this indicates that the NS is not capable of drawing a full 2A - I have not put a meter on it, but I would bet that it limits itself to somewhere just under an amp in.

I have recently bought both a 2A wall charger and car charger and my phone does not recognise either of these as anything more than a 500mA source.
Is it really just a case of opening the car charger up and shorting out pins 2 & 3? they are currently not connected to anything in the charger.

If it's indeed a matter of shorting the data lines, then I think you can skin the wire as suggested by others, but then cut the data lines, short the end that leads to the phone, leave the end to the computer open. I think it's the phone that tries to determine whether the data lines are shorted.
Edit: Can someone measure the continuity between the data pins with the stock charger? I wonder if they are shorted. I'm still waiting for my Nexus S to arrive, so can't test it.

Yup, the data lines in the stock Nexus S charger ARE shorted.
I just modified a cheap 1A car charger by popping it open, soldering the 2 data lines together and putting it back.
The report on the Nexus S before I did this (*#*#4636#*#*) said "USB", and afterwards it now says "AC".
I will report back after I make a road trip if this improves the GPS + Pandora + Screen in car situation. I suspect it will.
----------------
Yup, the car charger seemed to actually maintain and increase the battery this time. Seems good.

The NS supports chargers output to a max of 1000mA, as it says on the back of it, where the battery resides.

Related

Friend purchasing nook for me. Should I get anything else?

I have a friend who is visting the US (I'm from Canada) and I asked him to pick me up a nook. Not finding clear info in some of the reviews, mainly concerned about charging.
This charges over usb when hooked up to your computer right? Just want to make sure it doesn't use a proprietary cable for charging. I read on the ipad side, that older computers don't give out enough power to charge over usb, is that an issue with the nook?
What adapters/cables does it come with exactly? And is it just a standard mini-sub for the charging?
Also, this has a headset jack correct? I've read no bluetooth, I guess there's no way to get a mic working on this then.
Micro USB, will charge VERY slowly using a computer. Includes a 2amp wall socket and special cable to quick charge (still micro usb, just more pins). Has a headset port but does not come with a headset.
I've only had a few mobile devices. I read the ipad can charge over usb if the mobo supports giving out that extra juice. Some mobo's have a new firmware update to enable this.
The connector is micro-usb but just more pins. Hmm. so if the cable breaks or I misplace it no other micro-usb will charge it?
edit: i read a little more and found that it's 30 pin proprietary cable to speed up charging. I also read the galaxy tab does something similar.
Does anyone know if they use the same pin configuration? probably not, but I can get tab usb cables here.
I know you didn't ask for it but I'll tell you anyway
In case you are worrying about registering your device (mandatory at initial setup).
I'm NOT in the US and it worked fine.
Good to know. Thanks.
But I'm more concerned about charging it and relying solely on their cables.
I read the ipad can trickle charge on newer computers but some wouldn't provide enough power. Asus et al have released utilities to increase the power to the usb ports.
I can't post the links but endgadget has an article about it providing links to those utilites. They just talk of apple devices but does this work with the nook?
It comes with a charger for US-type sockets and only if you charge your nook with this (and yes, it is proprietary ) it'll charge quickly. It does seem to charge when you connect it to a standard PC USB port but at an extremely low rate.
On the device Micro-USB (not Mini) is used.
You say it does seem to, do you mean from personal experience? How slow? It sounds like that if you do own one it was so slow you didn't let it finish.
Like if it's 8hrs overnight, I can live with that, but I want to confirm that there is a plan b and not solely rely on their cables.
And as I mentioned asus and others released utils to give more power output to the usb (although these seem like their were only created for ipads). Wondering if those utils speed things up.
for ex, google asus ai charger to see what I mean.
I received my nook Color a mere few hours ago so I can't tell you a lot about its charging behavior It "seems" to load slower via standard USB... if you want to know about the details check one of the large threads on the NOOK and its rooting. I remember reading some information about the USB connector and its peculiarities there.
Ah you just got it. I see.
I found this on the root thread:
'
"There are 12 pins coming off the connector. It looks like there are no pins for the standard micro USB portion, only the extended 12 pins. 2 pins are used to bring in +5V, 2 pins are for signal ground providing a hefty circuit for the 2A charging. USB takes up two pins, and as far as I can tell 2 more are for each LED via current limiting resistors. Two more pins go to discretes that I haven't identified, and two more pins are unconnected. I'll take my scope to them when I have some time."
Not sure what he means when he says no pins for the standard micro portion...
Maybe the plug doesn't have standard USB pins, but the NOOK itself does have standard USB pins as well as the proprietary ones. Because I have trouble inserting the original B&N plug, I went out earlier today and bought a standard Micro USB cable...
I connected it to the nook and it said "not charging", so I went out to do some shopping (10-20 minutes max) and left it at 89%... when I came back it was at 93 %.
So it DOES in fact seem to charge albeit slowly.
Thanks. It's weird, lots of comments of its own cable not fitting properly.
As long as it charges with a normal cable I'm good.
I guess it is charging... however there is a slight chance, that it's NOT charging and the battery charge display is lying (de-calibrated). I don't think so, but I'll only know for sure after a few more days of using only the standard USB charger cable.

Anyway to charge at ~2 amps from computer?

Hi!
I just got my Nook and when I was about to charge it I realised I've lost my adapter for US plugs. Charging from the USB port on my computer is ridiculously slow, even with the Nook's USB/charger cable, and plugging it into my HTC charger makes that charger disconcertingly hot.
I reckon my computer's USB ports should be able to manage to provide at least a couple of amps, but, if I've understood things correctly, it won't provide anywhere near that much to the Nook unless the Nook asks for it.
So, is there any way to make the Nook ask for more juice?
Thanks in advance!
-- P
Animec said:
Hi!
I just got my Nook and when I was about to charge it I realised I've lost my adapter for US plugs. Charging from the USB port on my computer is ridiculously slow, even with the Nook's USB/charger cable, and plugging it into my HTC charger makes that charger disconcertingly hot.
I reckon my computer's USB ports should be able to manage to provide at least a couple of amps, but, if I've understood things correctly, it won't provide anywhere near that much to the Nook unless the Nook asks for it.
So, is there any way to make the Nook ask for more juice?
Thanks in advance!
-- P
Click to expand...
Click to collapse
USB ports are hardware limited to 500mA. It is part of the specification. Also most USB cables can't handle more current than this without damage. The Nook Color has a special cable with extra pins to handle the ~1900mA that it's charger puts out. The Nook doesn't 'Ask' for more juice, it's charger is capable of more current than a standard USB port, and the cable has the extra pins that carry the extra current. B&N did make it so that you could also charge it via standard USB-albeit more slowly. Your HTC charger is getting hot because it wasn't built to self-limit current to prevent damage to itself.
Ah, my bad. I read somewhere that USB devices can start out at 100 mA and then ask for more, but I don't know how I figured it could be as high as several amps >_< thanks for the clarification
mrmark93 said:
USB ports are hardware limited to 500mA. It is part of the specification. Also most USB cables can't handle more current than this without damage. The Nook Color has a special cable with extra pins to handle the ~1900mA that it's charger puts out. The Nook doesn't 'Ask' for more juice, it's charger is capable of more current than a standard USB port, and the cable has the extra pins that carry the extra current. B&N did make it so that you could also charge it via standard USB-albeit more slowly. Your HTC charger is getting hot because it wasn't built to self-limit current to prevent damage to itself.
Click to expand...
Click to collapse
Not really.. most laptop usb ports can handle ~800/900ma just fine. i.e. with my evo, it normally charges at 500ma using a standard microusb cable.. but if I use a special charge-only cable (middle pins are shorted out), then it charges at ~800ma..
-mark
diomark said:
Not really.. most laptop usb ports can handle ~800/900ma just fine. i.e. with my evo, it normally charges at 500ma using a standard microusb cable.. but if I use a special charge-only cable (middle pins are shorted out), then it charges at ~800ma..
-mark
Click to expand...
Click to collapse
Not surprising:
http://www.maxim-ic.com/app-notes/index.mvp/id/3241
What Your Mom Didn't Tell You About USB
With any standard, it's interesting to see how actual practice diverges from the printed spec or how undefined parts of the spec take shape. Though USB is, with little doubt, one of the best thought out, reliable, and useful standards efforts in quite some time, it has not been immune to the impact of the real world. Some observed USB characteristics that may not be obvious, yet can influence power designs, are:
USB ports do NOT limit current. Though the USB spec provides details about how much current a USB port must supply, there are mile-wide limits on how much it might supply. Though the upper limit specifies that the current never exceed 5A, but a wise designer should not rely on that. In any case, a USB port can never be counted on to limit its output current to 500mA, or any amount near that. In fact, output current from a port often exceeds several Amps since multi-port systems (like PCs) frequently have only one protection device for all ports in the system. The protection device is set above the TOTAL power rating of all the ports. So a four-port system may supply over 2A from one port if the other ports are not loaded. Furthermore, while some PCs use 10-20% accurate IC-based protection, other will use much less accurate poly-fuses (fuses that reset themselves) that will not trip until the load is 100% or more above the rating.
USB Ports rarely (never) turn off power: The USB spec is not specific about this, but it is sometimes believed that USB power may be disconnected as a result of failed enumeration, or other software or firmware problems. In actual practice, no USB host shuts off USB power for anything other that an electrical fault (like a short). There may an exception to this statement, but I have yet to see it. Notebook and motherboard makers are barely willing to pay for fault protection, let alone smart power switching. So no matter what dialog takes place (or does not take place) between a USB peripheral and host, 5V (at either 500mA or 100mA, or even maybe 2A or more) will be available. This is born out by the appearance in the market of USB powered reading lights, coffee mug warmers, and other similar items that have no communication capability. They may not be "compliant," but they do function.
Click to expand...
Click to collapse
I'll echo the fact that while USB as a spec isn't limited though sometimes a computer manufacturers will place a limit on it. MacBook Airs won't put out more than 500ish, for instance. The reason for that, I believe, is because Apple wanted to keep the power brick as small as possible (it's significantly smaller than the MacBook Pro's), which meant that the maximum wattage passing through the brick was limited. Since Apple didn't want the MBA to use more power than it could pull through the cord, it limited the power output of the USB ports. I've never needed more than 500 before I got the NC, so I never really cared (and I still don't).
But it is a thing.
Animec said:
Not surprising:
http://www.maxim-ic.com/app-notes/index.mvp/id/3241
Click to expand...
Click to collapse
And, for example, some motherboards have a feature that is a perfect example of bending the standards.
http://www.gigabyte.com/microsite/185/on-off-charge.htm
http://semiaccurate.com/2010/04/23/gigabyte-launches-charge-apple-products/
So, the HTC charger charged it from non-booting to full (ish) charge in 3 - 4 hours, and this time it didn't feel particularly hot. Not sure how or why, but this is certainly a relief
Why not just get a new adapter, they're not expensive.
Sent from my NookColor

Make non-motorola charger work?

So this is my first motorola and I had heard of the issues they have with non motorola chargers. Now I am experiencing it first hand. With the same ac charger I have charged many phones with and is capable of 1 amp output (D4 charger is only rated at 850 mA) my D4 struggles. With the device off it charged painfully slowly. While on it cannot even charge. It discharges while plugged in despite the charging indicator and reporting "charging (AC)" in status.
How does it know it is not a moto charger? Is it just about the resistance between the data pins? For most other phones shorting the data pins on the charger indicates to the phone that it is a high current charger and not a computer USB port. Is there a similar trick for motorola phones? I would rather not have to purchase an overpriced moto oem car charger. I have a perfectly fine 1.2 amp car charger soldered directly into my car's 12v system behind the dash. Can I make it work?
Thanks!
On a regular basis I successfully charge my D4 using both a charger from a Samsung Reality feature phone and from a B&N Nook Simple Touch, in addition to the one that came with it. I've also used a variety of car chargers.
Sent from my DROID4 using XDA
Actually, so far I have only one charger that had any trouble charging the phone (it was a $3 charger with 2 USB ports), but the $3 charger with ONE USB port works fine, as does the Nook Color charger, Blackberry charger, and Samsung charger I have tried it with, as well as both my old car charger and Lenovo's always-on charging port on their laptops.
JKingDev said:
So this is my first motorola and I had heard of the issues they have with non motorola chargers. Now I am experiencing it first hand. With the same ac charger I have charged many phones with and is capable of 1 amp output (D4 charger is only rated at 850 mA) my D4 struggles. With the device off it charged painfully slowly. While on it cannot even charge. It discharges while plugged in despite the charging indicator and reporting "charging (AC)" in status.
How does it know it is not a moto charger? Is it just about the resistance between the data pins? For most other phones shorting the data pins on the charger indicates to the phone that it is a high current charger and not a computer USB port. Is there a similar trick for motorola phones? I would rather not have to purchase an overpriced moto oem car charger. I have a perfectly fine 1.2 amp car charger soldered directly into my car's 12v system behind the dash. Can I make it work?
Thanks!
Click to expand...
Click to collapse
Not sure how it knows one way or the other. I've successfully used a few LG chargers to charge my D4. The only really hickup I've ran into is the usb cables from those lg chargers won't sync data to the phones when plugged into a computer, they'll still charge off the usb port but won't read as a usb connection to the computer.
Heh, captcha is trynply.
Every charger I've used, including an old charger for an EN-V, kindle, supplied, and various other phone chargers works just fine with this phone. Probably have a bad charger, guy.
Thanks for the replies. I guess I was wrong. My modded car charger works just fine. I guess its just time to retire the old charger that I have been using. I think it might be my old nexus one charger.
A more important question would be does the thing charge over computer-bound USB ports?
When you're without a charger, but there's a USB cable that fits your phone, sometimes a regular USB data port is the only that is around... even though it might take a really long time.
Try a computer bound USB port, then try your actual charger, again. Or do the hard reset (vol down plus power, hold until it actually does it), which is just like pulling the battery.
See how that goes.
Chris
RueTheDayTrebek said:
A more important question would be does the thing charge over computer-bound USB ports?
When you're without a charger, but there's a USB cable that fits your phone, sometimes a regular USB data port is the only that is around... even though it might take a really long time.
Try a computer bound USB port, then try your actual charger, again. Or do the hard reset (vol down plus power, hold until it actually does it), which is just like pulling the battery.
See how that goes.
Chris
Click to expand...
Click to collapse
It does in fact charge via USB port. In fact, it has a 'charge only' mode. Depending on how much juice your port puts out, and what you are doing with the phone, it will charge slowly/not at all, though.
from my experiences, the droid 4 will not accept lg microusb cables, the charging bricks work tho. i use a blackberry microusb on mine along with a Logitech and the stock moto ones. 1.2 amps is a bit high but not crazy sounding. personally, I charge at 1 amp.

[Q] Need a better charger cable when plugged into my work computer

So to my understanding the 2a that is supplied to our phones when plugged into the wall is due to the wall part and not the cable. Is there any difference in the cables that could provide me a better charge? I leave my phone plugged into my work computer most of the day and it doesnt seem to give it much of a charge. Is this something wrong with the USB port itself (can you systematically change the output provided on your computer? I wonder if t would make a difference in the front vs back usb ports.
Also I am not against getting a nice dock for it while its here at work but I like to keep it in landscape mode. If anyone knows of one available to keep it on with a clock or something and still eb able to charge it I would be appreciative.
Thanks in advance.
The computer usb ports are normally limited to 500mA. The oem wall charger is 2000mA. So you get 4x the current when plugged into the wall. On top of that some chargers have basic circuits in them that the phone recognizes so it knows to pull more current. If you want a fast charge use the supplied wall charger.
Sent from my SCH-I605 using xda app-developers app
i do wonder about this too, as my iphone will charge (sufficiently) thru pc, but the note 2 takes forever
Do they sell or could you make a cable that has two usb plugs on the end, one that will plug into the computer for syncing and one that could plug into the oem wall charger for fast charging.
I would think you could use the two data wires in the usb to connect to the computer and the two power wires to go to the wall charger. Would be really easy to do and only require an old usb cable for the second male USB A end.
Does anybody have any experience with this or know if its possible. The dock seems to have this ability but I would prefer not to purchase an expensive dock.
Some of the more advanced PC motherboards out there have one or two high-current USB ports that can be set for dedicated smartphone/tablet charging. Most of these are Intel Sandy boards as far as I know.
FWIW the Perseus kernel charges far faster IME than the stock kernel.
The iPhone charges "more" than the Note 2 because the iPhone's battery has a smaller capacity. (1440 mAh vs 3100 mAh) so basically every 1% of battery on the Note 2 is over 2% on the iPhone.
ronzza said:
i do wonder about this too, as my iphone will charge (sufficiently) thru pc, but the note 2 takes forever
Click to expand...
Click to collapse
A
Before I bought the note, I had a sgs with cm10 and a kernel that supports fast charge. It neglects the pins used for data signal on the usb and makes it a power source only, and I'm pretty sure I got around 1mah with this method though I didn't measure it.
Should be no reason for it not to work on our phones if a kernel supports the method.
Sent from my GT-N7100 using Tapatalk 2
USB 3.0 changes from 2.0
MDavisiw said:
So to my understanding the 2a that is supplied to our phones when plugged into the wall is due to the wall part and not the cable. Is there any difference in the cables that could provide me a better charge? I leave my phone plugged into my work computer most of the day and it doesnt seem to give it much of a charge. Is this something wrong with the USB port itself (can you systematically change the output provided on your computer? I wonder if t would make a difference in the front vs back usb ports.
Also I am not against getting a nice dock for it while its here at work but I like to keep it in landscape mode. If anyone knows of one available to keep it on with a clock or something and still eb able to charge it I would be appreciative.
Thanks in advance.
Click to expand...
Click to collapse
Ok so this is my understanding. If it's a laptop they usually only have one usb port inside. its then run to a hub and from there split to all the other laptop usb ports that you see on the outside. so the power is usually lower than the 500ma. I thought the cable from cableforge.com was bad but it was just the low power from the laptop port.
This said USB 3.0 runs on its own line so it usually works better. now this is where i may be wrong isnt the usb 3.0 more than 500ma?
Excelus said:
The iPhone charges "more" than the Note 2 because the iPhone's battery has a smaller capacity. (1440 mAh vs 3100 mAh) so basically every 1% of battery on the Note 2 is over 2% on the iPhone.
A
Click to expand...
Click to collapse
The iphone and most other phones charge "more" because they pulls the entire 500mA that the usb spec allows. For some reason, Samsung phones only pull 96mA over usb. A new cable won't make a difference.

Fast charging questions

Been looking for a fast car charger as well as a second ac charger.
I do have questions about usb cables though.
Which is responsible for shorting out the data pins...the charger, or the cable?
Also, while experimenting with my stock charger, I noticed a couple.of things...
I have an old 9ft cable I had along time ago, as well as a 6ft usb3 extension cable.
Using the stock charger
With 9ft cable, I get 13% per hour
With usb3 ext + stock cable, I get 25% per hour
With just the stock cable, I get 35% per hour.
(These are all according to battery monitor widget)
Should I be looking for a specific type of cable as well? I would really like a long cable so even if I bought a second oem charger, I would like to buy a non stock cable.
swyped all these spelling errors from my galaxy note 2
finalhit said:
Been looking for a fast car charger as well as a second ac charger.
I do have questions about usb cables though.
Which is responsible for shorting out the data pins...the charger, or the cable?
Also, while experimenting with my stock charger, I noticed a couple.of things...
I have an old 9ft cable I had along time ago, as well as a 6ft usb3 extension cable.
Using the stock charger
With 9ft cable, I get 13% per hour
With usb3 ext + stock cable, I get 25% per hour
With just the stock cable, I get 35% per hour.
(These are all according to battery monitor widget)
Should I be looking for a specific type of cable as well? I would really like a long cable so even if I bought a second oem charger, I would like to buy a non stock cable.
swyped all these spelling errors from my galaxy note 2
Click to expand...
Click to collapse
You're probably referring to the charge-only usb cables with the data pins shorted out - it is the cable which has the data wires shorted out; the wall charger only uses 2 out of the 4 usb wires, so there's no need to have anything shorted out on the charger side.
It's useful to share what you have noticed, but the general idea is that the longer the usb cable, the more it would take to charge because the extra resistance along the cable which is created; in a similar way you lose current if you use any extenders, passive usb hubs etc - how much? it really depends on what you pick, you can have it calculated / measured. A higher gauge usb cable would give you faster charge times, so pick a quality cable, even if it's a non-OEM and you'll get similar results to the original cable.
tbukkos said:
You're probably referring to the charge-only usb cables with the data pins shorted out - it is the cable which has the data wires shorted out; the wall charger only uses 2 out of the 4 usb wires, so there's no need to have anything shorted out on the charger side.
It's useful to share what you have noticed, but the general idea is that the longer the usb cable, the more it would take to charge because the extra resistance along the cable which is created; in a similar way you lose current if you use any extenders, passive usb hubs etc - how much? it really depends on what you pick, you can have it calculated / measured. A higher gauge usb cable would give you faster charge times, so pick a quality cable, even if it's a non-OEM and you'll get similar results to the original cable.
Click to expand...
Click to collapse
but the OEM cable can also be used for data transfers, surely, it's data pins are not shorted out?
it is the charger that normally has data pins shorted, and I have modified a few chargers to achieve this.
In the OSmonitor app the is a misc tab that shows if you are charging from AC or USB, there must be a way of finding the charging current, on one of my old phones it was displayed in dmesg.
Dont forget that the % per hour will vary according to how full the battery is, slowing down as it gets more full.

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