Database Develop

[Q] Run Nexus One on AC power alone

When booting the Nexus One, for as long as the X logo is displayed the battery can be removed and the phone will stay on and remain booting on USB power alone - try it!
Once the boot process continues past the X disappearing however, this no longer works. Regardless of USB power being present the phone will switch off as soon as the battery is removed.
I wonder: Is this behaviour configurable? Is there any kernel code that could be altered to allow the Nexus One to continue running on USB power alone?
I have a few spare batteries, when charging them up it would be useful to be able to switch batteries out while the phone continues to run.

Wrong section, but yeah great idea. I could do this on my PSP, and was quite disappointd when I couldn't do it my N1.

Very good job to find that. It will be awesome to find a way to make this.
It will be good to tether usb and dont charge/discharge the batteri to
make life shorter.
My Dell Axim x51 does that and rules without battery, its good to put the tom tom in car and not to worry about battery.
Will be good to all that have access to a computer in work.

The battery has 4 contacts and the phone connects to them using 6 pins.
*Wild Guess* These are probably for +/- charging +/- discharging
It may be possible to connect the charging pins to the discarging ones to trick it into thinking there is a battery. (Dont experiment and blow yourself up if you dont know ) The charging voltage/current may need to be stepped up/down.
Note: I have a battery charger from ebay and it only uses the outer pins to charge the battery.

britoso said:
The battery has 4 contacts and the phone connects to them using 6 pins.
*Wild Guess* These are probably for +/- charging +/- discharging
It may be possible to connect the charging pins to the discarging ones to trick it into thinking there is a battery. (Dont experiment and blow yourself up if you dont know ) The charging voltage/current may need to be stepped up/down.
Note: I have a battery charger from ebay and it only uses the outer pins to charge the battery.
Click to expand...
Click to collapse
I have a battery which is marked with the following. (from outside to inside)
| + | DQ | T | - |
The charger that I have uses + and - only.
Not sure what they mean though T= Temp? DQ = Data?

The other pins are to "split the voltage". That's how you can have a 3.7V battery putting out multiple levels of voltage (1.2, 1.8, 3.7 for example). I would imagine a common negative, then the "master" 3.7V positive, then a couple of other voltage levels. I'll get my multimeter later on and play with it, just for kicks and giggles, but that's the same reason why laptop batteries have multiple contacts (though the motherboard still needs to be able to step voltage coming in from the PSU, in case the battery is missing...it's just more efficient to be able to bring it in directly from the battery at the correct voltage level.

MaximReapage said:
The other pins are to "split the voltage". That's how you can have a 3.7V battery putting out multiple levels of voltage (1.2, 1.8, 3.7 for example). I would imagine a common negative, then the "master" 3.7V positive, then a couple of other voltage levels. I'll get my multimeter later on and play with it, just for kicks and giggles, but that's the same reason why laptop batteries have multiple contacts (though the motherboard still needs to be able to step voltage coming in from the PSU, in case the battery is missing...it's just more efficient to be able to bring it in directly from the battery at the correct voltage level.
Click to expand...
Click to collapse
If it were to just step down voltages, how does the phone get the data of battery condition? I think there's more to it than just that.

I can't do this on my Nexus. I just tried it, because I have 2 spare uncharged batteries I would like to charge while the phone is on. I turned off the phone, turned it on while plugged in to its AC charger, removed the battery while it was on the Google X (static, not animated) logo, and the phone turns off. The little LED indicator blinks interchangeably between orange and green and the phone remains off.
I'm on AT&T Nexus One, with a custom bootloader, and a rooted, deodexed, lightly modified stock ROM.

Thread moved to Q&A, and [Q] tag added. This seems very interesting.

momentarylapseofreason said:
If it were to just step down voltages, how does the phone get the data of battery condition? I think there's more to it than just that.
Click to expand...
Click to collapse
I would imagine by measuring actual vs. desired voltage, as well as voltage "jitter"

wornbat said:
I have a battery which is marked with the following. (from outside to inside)
| + | DQ | T | - |
Not sure what they mean though T= Temp? DQ = Data?
Click to expand...
Click to collapse
Correct indeed. This battery only supplies one voltage.
You should check the battery calibration thread in the development section for more info.
The battery has nothing to do with this however. The kill switch is somewhere in the software.
When the phone locks up and the battery is removed while on USB, it won't turn off.
There's a good reason for this to exist though. The battery acts as a regulator and current supplier when the USB line can't provide enough.
Disabling this protection will make the system unstable when overloaded.

MaximReapage said:
The other pins are to "split the voltage". That's how you can have a 3.7V battery putting out multiple levels of voltage (1.2, 1.8, 3.7 for example). I would imagine a common negative, then the "master" 3.7V positive, then a couple of other voltage levels. I'll get my multimeter later on and play with it, just for kicks and giggles, but that's the same reason why laptop batteries have multiple contacts (though the motherboard still needs to be able to step voltage coming in from the PSU, in case the battery is missing...it's just more efficient to be able to bring it in directly from the battery at the correct voltage level.
Click to expand...
Click to collapse
The other pins are definitely not to split the voltage. I have opened one of my dead batteries and behind the connector pads there is a circuit board with several SMD devices on it. there are only two straps going off to the battery on either side.

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

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

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

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

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

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

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

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

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

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

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

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

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

Deciphering the Nexus 7 Automatic Input Current Limit (for chargers)

For the time being this is going to be in Accessories, but eventually it might get moved to Development as I get even more data. It's borderline at the moment.
It's been known for a while that the Nexus 7 is finicky about power supplies. In addition to the usual requirements for a power supply that complies with the USB Battery Charging Standard (D+ and D- shorted by the supply), which makes it VERY hard to find good supplies as most use Apple's nonstandard convention - The Nexus 7 seems to be VERY finicky about supplies which drop their voltage under load. Samsung tablet supplies will charge the N7 faster than the stock supply.
The charger controller chipset in the N7 is a Summit SMB347, same as found in a number of Samsung tablets. No datasheet is available for this chipset, but we do know it has an Automatic Input Current Limiting (AICL) feature - If the power supply "browns out", it will reduce current demand until the supply voltage raises to above the trip threshold.
Previously, I only had the ability to measure battery input current using CurrentWidget, but the top of my Christmas wishlist was an adjustable bench power supply. It has adjustable voltage AND an adjustable current limit - so I can limit the current delivered to the N7 and determine what voltage it settles at. If the voltage kept bouncing between two values, I recorded the voltage as the halfway point. E.g. if it bounced between 5.1 and 5.2, I recorded it as 5.15.
A picture of my setup is at:
https://plus.google.com/u/0/101093310520661581786/posts/gkbHaKKDnj6
Components:
Sinometer HY3005D from Mastech (Adjustable bench supply, 0-30v 0-5A)
22 gauge solid wire (the best USB cables I've seen are only 24 gauge - lower gauge = thicker wire)
Sparkfun MicroUSB breakout with D+ and D- shorted
Here are the results (Bear with me as I try to figure out how to properly format a table here on XDA... The HTML tag doesn't work as expected...):
HTML:
<table border="1">
<tr><td>Amperage Limit</td><td>Voltage</td></tr>
<tr><td>1.85</td><td>5.15</td></tr>
<tr><td>1.80</td><td>5.0</td></tr>
<tr><td>1.70</td><td>4.9</td></tr>
<tr><td>1.60</td><td>4.9</td></tr>
<tr><td>1.50</td><td>4.8</td></tr>
<tr><td>1.40</td><td>4.8</td></tr>
<tr><td>1.30</td><td>4.7</td></tr>
<tr><td>1.20</td><td>4.7</td></tr>
<tr><td>1.10</td><td>4.6</td></tr>
<tr><td>1.00</td><td>4.55</td></tr>
</table>
Below 1A, I think the tablet goes into a more severe AICL mode - it will drop to around 600-650 mA, the power supply will exit current limiting (back up to 5.1 volts), and current will not go up until the device is unplugged and replugged.
One observation here - If the voltage drops 0.2 volts, you lose 400 mA of charge current. Many previous efforts here put an ammeter in series with the power supply - many ammeters drop 0.1-0.2 volts under load! The ammeter used by those previous effort was having SIGNIFICANT effect on the results.

Reserved - future analysis of how various chargers behave under load. Do they REALLY meet their ratings?
May be posted in Hardware Hacking and linked from here instead.

Reserved for work on trying to change the SMB347 AICL behavior.

Even if the amperemeter drops 0.1-0.2 V under various loads, you can stick a voltmeter after the amperemeter (i.e. parallel to the device only) and you should have a pretty accurate reading of the voltage on the device alone since voltmeters are pretty high impedance. And to compensate for the loss, just increase the supply voltage a bit.

Entropy512 said:
Stuff.
Click to expand...
Click to collapse
I think you may be trying to read too far into this.
I charge my Nexus 7 off of a generic 2A/5V X4 output charger, and off the stock charger, and off the woman's kindle fire charger, and off a 2A car adapter. All of it works just fine.
I think the real problem comes from people using chargers that aren't able to produce enough current (thus the voltage drop you're trying to measure for). But honestly, this tablet lasts incredibly long on a charge, and takes almost no time to get back to 100%. Aside from if you're using it in your car as a long term audio/gps/hspa unit, all at once, why even bother taking out your meter?
TLDR: Buy a charger that is rated for 5V, 2A, and go back to having a good holiday instead of trying to measure it. Granted, I understand you're interested in finding out the how's and why's, but I haven't found any issue with charging the Nexus 7 on any charger I own, because I only buy ones that are rated for 2A or above draw. I won't get out the Fluke to test what it's pulling on each one, but it seems to charge very quickly on all of the above. 1%-100% in the time it takes me to not care, anyways.

bladebarrier said:
I think you may be trying to read too far into this.
I charge my Nexus 7 off of a generic 2A/5V X4 output charger, and off the stock charger, and off the woman's kindle fire charger, and off a 2A car adapter. All of it works just fine.
I think the real problem comes from people using chargers that aren't able to produce enough current (thus the voltage drop you're trying to measure for). But honestly, this tablet lasts incredibly long on a charge, and takes almost no time to get back to 100%. Aside from if you're using it in your car as a long term audio/gps/hspa unit, all at once, why even bother taking out your meter?
TLDR: Buy a charger that is rated for 5V, 2A, and go back to having a good holiday instead of trying to measure it. Granted, I understand you're interested in finding out the how's and why's, but I haven't found any issue with charging the Nexus 7 on any charger I own, because I only buy ones that are rated for 2A or above draw. I won't get out the Fluke to test what it's pulling on each one, but it seems to charge very quickly on all of the above. 1%-100% in the time it takes me to not care, anyways.
Click to expand...
Click to collapse
Except that many chargers, even the ONE THAT COMES WITH THE DEVICE, aren't capable of delivering 5v 2A even if they may claim to do so. They may be capable of 4.8v 2A - but as the data I've taken shows, a charger that can only do 4.8v 2A will only charge the N7 at 1.4-1.5 amps. If the charger drops to 4.7v under load, it'll drop to only 1.2A or so.
More data (taken using CurrentWidget):
Idle load with screen at max brightness: 500 mA drain reported by CW
Current entering battery when screen at max brightness: 900-950 mA with stock Asus charger, giving approx. Since system drain under these conditions is 0.5A, that gives 1.4-1.45A into the device, consistent with a charger that is dropping to 4.8v under load.
Current entering battery with a Samsung Galaxy Tab charger: 1300 mA, giving a total of 1.8A into the device (almost the maximum the device will pull given a solid stiff rail)
Current entering battery with the power supply used in the tests above: 1330 mA, giving a total of 1.83A into the device (power supply itself reported 1.86 in this state).
The stock Asus charger that ships with the device underperforms by 400 mA when used with this device. Many "2.1A" chargers underperform even more (I'll run some tests with the Scosche reVIVE II later, but if memory serves me correctly, it's more appropriately rated 1A...)

gokalp said:
Even if the amperemeter drops 0.1-0.2 V under various loads, you can stick a voltmeter after the amperemeter (i.e. parallel to the device only) and you should have a pretty accurate reading of the voltage on the device alone since voltmeters are pretty high impedance. And to compensate for the loss, just increase the supply voltage a bit.
Click to expand...
Click to collapse
Yup. If I didn't have a bench supply with an adjustable current limit, I could've done this. Problem is even a few tenths of a volt difference makes a significant current difference - it's easier to adjust the current limit if you've got a supply that allows it.

Entropy512 said:
Except that many chargers, even the ONE THAT COMES WITH THE DEVICE, aren't capable of delivering 5v 2A even if they may claim to do so. They may be capable of 4.8v 2A - but as the data I've taken shows, a charger that can only do 4.8v 2A will only charge the N7 at 1.4-1.5 amps. If the charger drops to 4.7v under load, it'll drop to only 1.2A or so.
More data (taken using CurrentWidget):
Idle load with screen at max brightness: 500 mA drain reported by CW
Current entering battery when screen at max brightness: 900-950 mA with stock Asus charger, giving approx. Since system drain under these conditions is 0.5A, that gives 1.4-1.45A into the device, consistent with a charger that is dropping to 4.8v under load.
Current entering battery with a Samsung Galaxy Tab charger: 1300 mA, giving a total of 1.8A into the device (almost the maximum the device will pull given a solid stiff rail)
Current entering battery with the power supply used in the tests above: 1330 mA, giving a total of 1.83A into the device (power supply itself reported 1.86 in this state).
The stock Asus charger that ships with the device underperforms by 400 mA when used with this device. Many "2.1A" chargers underperform even more (I'll run some tests with the Scosche reVIVE II later, but if memory serves me correctly, it's more appropriately rated 1A...)
Click to expand...
Click to collapse
Interesting.
Are you getting the same readings when the device is turned off, to ensure there isn't a possible software issue? Is this purely on the stock ROM/kernel, or are you using a custom one?
With the Droid X, there were some concerns that it was unable to charge a fully discharged battery if not on a stock ROM, because Moto implemented measures in the "bloat" that allowed it to do so when it would normally not be capable in pure Android. I remember people having to cut wires to charge batteries externally, if they ran out of juice while trying to flash a ROM that was not Moto based. The whole concept seemed absurd to me, yet that was clearly the case. A dead Droid X could charge normally, if on the Moto software, but could not charge at all, if on AOSP if the battery was completely discharged prior to the attempt.
Just throwing out some ideas. I don't have your level of equipment to test it out at home, but I could take mine into the EE lab and see what one of the students can discern.
Is it possible that some of this is because of the pogo connection, and that may not be sorted out well enough, as such causing complications to the circuit?
EDIT: What is the accuracy of Current Widget? I tried it on my Nexus 7, and it was reporting some absurd numbers that didn't appear to be accurate. I would be charging at normal speed, and it would show me as discharging. The Nexus 7 would go back to 100%, and the whole time it would read as if I was losing power. I uninstalled it, figuring there is a compatibility issue with either JB or the device.

bladebarrier said:
Interesting.
Are you getting the same readings when the device is turned off, to ensure there isn't a possible software issue? Is this purely on the stock ROM/kernel, or are you using a custom one?
With the Droid X, there were some concerns that it was unable to charge a fully discharged battery if not on a stock ROM, because Moto implemented measures in the "bloat" that allowed it to do so when it would normally not be capable in pure Android. I remember people having to cut wires to charge batteries externally, if they ran out of juice while trying to flash a ROM that was not Moto based. The whole concept seemed absurd to me, yet that was clearly the case. A dead Droid X could charge normally, if on the Moto software, but could not charge at all, if on AOSP if the battery was completely discharged prior to the attempt.
Just throwing out some ideas. I don't have your level of equipment to test it out at home, but I could take mine into the EE lab and see what one of the students can discern.
Is it possible that some of this is because of the pogo connection, and that may not be sorted out well enough, as such causing complications to the circuit?
EDIT: What is the accuracy of Current Widget? I tried it on my Nexus 7, and it was reporting some absurd numbers that didn't appear to be accurate. I would be charging at normal speed, and it would show me as discharging. The Nexus 7 would go back to 100%, and the whole time it would read as if I was losing power. I uninstalled it, figuring there is a compatibility issue with either JB or the device.
Click to expand...
Click to collapse
I can only confirm CW works properly on CM10. It is completely nonoperational in stock (as the code was disabled), and they did something in that area in 4.2 that I haven't taken a look at yet. I know the voltage value was off by a factor of 1000 in stock 4.1.
As to software issues - there are none other than whatever nonvolatile defaults are preprogrammed into the SMB347. If you look at the SMB347 driver for grouper you'll see that it does almost nothing in terms of configuring current limits and such, relying on the internal NV defaults. (Very different from Kindle Fire and Note 10.1, which perform quite a lot of configuration of the chip, not relying on internal NV defaults.) I've seen people report similar behavior on multiple kernels and firmwares.
Based on the Kindle Fire sources, there is at least one AICL setting that can be tweaked. However after looking at them further, I think that's the one that hits when the power supply droops to 4.5 volts. The question is whether the charger circuit is doing limiting before hitting that severe AICL threshold. When I get back from my holiday I'm going to try changing the threshold to 4.2 volts to see how things behave.

Entropy512 said:
I can only confirm CW works properly on CM10. It is completely nonoperational in stock (as the code was disabled), and they did something in that area in 4.2 that I haven't taken a look at yet. I know the voltage value was off by a factor of 1000 in stock 4.1.
As to software issues - there are none other than whatever nonvolatile defaults are preprogrammed into the SMB347. If you look at the SMB347 driver for grouper you'll see that it does almost nothing in terms of configuring current limits and such, relying on the internal NV defaults. (Very different from Kindle Fire and Note 10.1, which perform quite a lot of configuration of the chip, not relying on internal NV defaults.) I've seen people report similar behavior on multiple kernels and firmwares.
Based on the Kindle Fire sources, there is at least one AICL setting that can be tweaked. However after looking at them further, I think that's the one that hits when the power supply droops to 4.5 volts. The question is whether the charger circuit is doing limiting before hitting that severe AICL threshold. When I get back from my holiday I'm going to try changing the threshold to 4.2 volts to see how things behave.
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Click to collapse
You're way above my pay grade.... Yet I'll speculate further.
If it's hardware based, to drop the amperage draw, based on a voltage drop, and can be replicated in CM, then it could be an intentional protection circuit in the Lion battery itself. There are many Lion batteries that use protection circuitry these days, yet I don't know of anyone using aftermarket replacements for the Nexus 7, and so testing it could very well be basing the tests purely on the battery itself.
Maybe try running the tests directly to the battery, removed from the Nexus itself, and that will at least exclude the software and the hardware of the Nexus.
I could crack open the body and check the manufacturer, but if it's Panasonic or Sony, there's a reasonable chance that there are built in circuits on the Lion itself.
If you get identical readings, while running leads directly to the battery, the issue will be known immediately. If you don't, we can rule out one of the three options (battery, hardware, software). And you already ruled out most of the software.

bladebarrier said:
You're way above my pay grade.... Yet I'll speculate further.
If it's hardware based, to drop the amperage draw, based on a voltage drop, and can be replicated in CM, then it could be an intentional protection circuit in the Lion battery itself. There are many Lion batteries that use protection circuitry these days, yet I don't know of anyone using aftermarket replacements for the Nexus 7, and so testing it could very well be basing the tests purely on the battery itself.
Maybe try running the tests directly to the battery, removed from the Nexus itself, and that will at least exclude the software and the hardware of the Nexus.
I could crack open the body and check the manufacturer, but if it's Panasonic or Sony, there's a reasonable chance that there are built in circuits on the Lion itself.
If you get identical readings, while running leads directly to the battery, the issue will be known immediately. If you don't, we can rule out one of the three options (battery, hardware, software). And you already ruled out most of the software.
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Click to collapse
No way it's the battery itself. If you ran straight 5v into a LiIon/LiPo battery you'd blow it up (unless the protection circuitry kicked in). Running 5v straight into even a protected LiIon is an extremely bad idea.
It's something in how the SMB347 behaves - http://www.summitmicro.com/prod_select/summary/SMB347/SMB347.htm - Unfortunately there is no public datasheet, just a 1-2 page "product brief" with little detail, other than it does have some sort of automatic input current limiting. The SMB347 is the chip responsible for charging the battery safely, and basically anything related to charging the battery in the N7 is within that chip. Understand that chip and you understand everything about charging the N7.
The only technical detail we have about this chip resides in kernel source code for devices with the same chip - Samsung Note 10.1 and Kindle Fire both have a 347, and unlike the N7 which appears to use nonvolatile defaults burned into the chip, these devices touch the chip's registers. The KFire source has some info on how to change one of the AICL configurations.

Entropy512 said:
No way it's the battery itself. If you ran straight 5v into a LiIon/LiPo battery you'd blow it up (unless the protection circuitry kicked in). Running 5v straight into even a protected LiIon is an extremely bad idea.
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Click to collapse
Without a doubt!
I would never suggest someone use the method for normal charging. You would have to be capable of limiting the current, and be very careful, if testing in that manner.

I don't know how useful this comment will be, since there's no technical data, just empirical evidence, but I've used a friend's Nexus 7 charger several times on my Xperia S, that has fast charging enabled by default, and it charges noticeably faster than the charger that was packed with it (850 mA).
So, I'm inclined to think the culprit is the SMB347 chip.

FenrirMX said:
I don't know how useful this comment will be, since there's no technical data, just empirical evidence, but I've used a friend's Nexus 7 charger several times on my Xperia S, that has fast charging enabled by default, and it charges noticeably faster than the charger that was packed with it (850 mA).
So, I'm inclined to think the culprit is the SMB347 chip.
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Click to collapse
It's the SMB347 combined with the power supply. The PS is drooping a little bit (not significantly), and the SMB347 is being exceptionally finicky about the droop.
Supplies that don't droop (Samsung Tab chargers - FYI, the Note 10.1 also has an SMB347) are OK, that supply is likely OK with less finicky devices.
Next on my project list:
While the setup used here (22 gauge sold wire that is only a foot or so long) is ideal for eliminating voltage drop in the USB cable, I need to whip up a "universal charging adapter" between my bench supply and a female USB port that uses Samsung tablet resistances (which are also OK for most standard devices). That way I can see how my Note 10.1 behaves with a current limited supply.
A power supply tester - PWM out of an AVR microcontroller into an adjustable constant current load, ramp up the current draw and monitor the supply voltage with the uC to get an output I/V curve for various supplies.

current widget
My apologies for reviving such an old thread, but I have been searching for information about how the nexus 7 charges and why of acts so different with different chargers. Your posts have been very informative. I have found that my Verizon car charger will charge my nexus considerably faster than any other charger I have, including the one which came with the tablet.
I am curious to know how you were able to use current widget on this device. I am running cm10. Which kernel has support for current widget so that I may flash it? I am using battery widget for the time being and while of does give me a rough estimate, I would really like a real time reading.
Thank you for your time.

Crystawth said:
My apologies for reviving such an old thread, but I have been searching for information about how the nexus 7 charges and why of acts so different with different chargers. Your posts have been very informative. I have found that my Verizon car charger will charge my nexus considerably faster than any other charger I have, including the one which came with the tablet.
I am curious to know how you were able to use current widget on this device. I am running cm10. Which kernel has support for current widget so that I may flash it? I am using battery widget for the time being and while of does give me a rough estimate, I would really like a real time reading.
Thank you for your time.
Click to expand...
Click to collapse
I actually stumbled on an answer myself.
Franco Kernel r65 for 4.2.2 on CM 10.1 Provides battery current information =)

Here's what I've learned from a hardware perspective...
Posting this in a few places hoping it stimulates an answer to the problem....
We're working on a hardware + firmware + software product that uses an Android tablet, which right now is specifically the Nexus 7. We have found that the standard charge rate of the battery is insufficient to support tablet operation with a few sensors enabled and high screen brightness. Therefore, even if plugged in to a power source, the Nexus 7 discharges during normal use. The charging system cannot keep up with normal power requirements. That is a TERRIBLE hardware design decision.
Rather than guess at what is happening, or jump to conclusions based on various apps that claim to report current, we connected an actual ammeter (current meter) in line with the USB cable plugged in to a 2012-era Nexus 7 and ran a lot of experiments to characterize its behavior.
A few basic things to keep in mind:
* The current rating on a power supply/charger is the max current that device can provide. The device being charged controls how much current is actually drawn from the supply. A higher-current charger cannot, simply by virtue of its higher capacity, force more current into the device.
* USB hardware specs very clearly define the max current that a Portable Device (PD, in this case an N7) can draw from various power sources. Earlier posts in this thread properly referred to the names of the various types of ports including the one that we need, a Charging Downstream Port (CDP), which supports both data and higher charging current. A CDP uses certain voltage levels on its D+ and D- pins to signal the availability of greater current; a "dumb charger" can just short the two data pins together to signal the same thing, but obviously this won't work if you also want to pass data and not just charge the battery. (The "shorted data pins" trick is a documented way to let cheap chargers inform the PD of higher current capacity without having to add intelligence to the charger.)
* USB software specs also define how the PD can negotiate with the upstream port (in our case, a CDP), essentially letting the N7 specify how much current it wants to draw and letting the upstream port respond with approval or disapproval. In this case, the hardware does its thing, and then the software on both ends talks back and forth to agree on a (potentially higher) current rate.
I'll cut to the chase: The N7 never draws more than 440mA. Ever. With any charger, with any cable, with any combination we've tried. This includes the Asus-labeled 5V 2100mA OEM charger and the Asus-labeled OEM cable that came with the tablet. We really, really want it to, but we have not been able to figure out how to convince it to use more current (and thus stop draining the battery while plugged in). Yes, I've read the other comments in this thread that report higher currents and I don't know how to explain what they're seeing. But in a laboratory environment, with real test equipment run by Engineers, 440mA is the number.
On the hardware side, our product has a dedicated 5A 2000mA+ power supply for the N7 connection. This is really clean power - it's a little switching power supply with great filtering that powers nothing but the USB connector. An oscilloscope shows an absolute flat line, no ripple, no noise, nothing, even under load. We have tested its current output capacity and it goes well beyond 2000mA with no degradation of the voltage level nor quality. This power is as clean as its gets. The power is there if the N7 wants it.
On the software side, the N7 does in fact do the "USB software negotiation" for current and we tell the N7 that 2000mA is available. Nevertheless, the N7 always requests 500mA (we've captured and analyzed the USB data), and in reality never draws more than the 440mA mentioned above.
We cannot short D+ and D- since we need to communicate with the N7. But there are other tricks supported by the USB spec, including specific voltage levels on the data lines to indicate that the port to which the N7 is connected is a CDP. Briefly, a PD which takes advantage of a CDP first performs "primary detection" by looking at D- for 0.4-0.8VDC. If a voltage in that range is found, "secondary detection" causes the PD to apply voltage to the D+ pin looking for a pulldown resistance of (nominally) 19.5K.
So we added circuitry to provide this environment, thus indicating we are a CDP. Result: No change at all. The N7 draws 440mA with or without the CDP circuitry.
We kept at it for a long time, because we thought it strange that Asus would ship a 2100mA charger when a 500mA charger would suffice. We figured that was proof the N7 could charge at a higher rate. But after hours and hours of analysis, testing, experiments, etc. we were forced to conclude that the N7 simply never draws more than 440mA. Presumably its onboard charging circuitry cannot handle higher current rates. This is a real shame, because it means the Nexus 7 cannot be used in kiosk mode - it cannot run indefinitely when plugged into external power. It will always require some "down time" to recharge its battery. That's fatal to a lot of applications for this tablet, including ours.
We have not yet tested a 2013 N7, but we're hopeful it has a better charging circuit.

SpokaneNexus said:
We cannot short D+ and D- since we need to communicate with the N7. But there are other tricks supported by the USB spec, including specific voltage levels on the data lines to indicate that the port to which the N7 is connected is a CDP. Briefly, a PD which takes advantage of a CDP first performs "primary detection" by looking at D- for 0.4-0.8VDC. If a voltage in that range is found, "secondary detection" causes the PD to apply voltage to the D+ pin looking for a pulldown resistance of (nominally) 19.5K.
Click to expand...
Click to collapse
I never saw this particular post of yours until trying to find this old post of mine.
N7 does not support CDP (Charging Downstream Port) detection. Few Android devices do. (N7 2012 most definitely does not, and I'm fairly certain N7 2013 doesn't either). If it sees a downstream port, it assumes it's an SDP (Standard Downstream Port) with 500 mA current limit. This is a fundamental requirement of the USB standard - don't pull more than 500 mA from a host unless you support CDP detection and detect a CDP.
N7 does support DCP (Dedicated Charging Port) detection. N7 will ABSOLUTELY pull more than 500 mA from a DCP (this includes the wall supply) when D+ and D- are shorted.
If you want to communicate with the device and supply more than 500 mA, you need either a device that supports CDP detection (rare) or you need to violate the standard. This can be done with kernel modifications that override the current limit when an SDP is detected - this is usually a HORRIBLE idea but is acceptable in a specific case like yours. (Some kernel hackers refer to this as "USB Fast Charging").

Sorry for posting on an old thread, but it is still an issue, and i am determined to find a fix.
I bought a thick 20awg cable, and that seems to do the job, but i don't use my n7 enough to see if it really does.
You referenced the kernel a few times in reference to the chip that controls the charging.
I was wondering if it would be possible to modify kernel sources to change the way the chip behaves, although i dont have many hopes, because i imagine it would have already been done
i was thoroughly engaged in this issue, and even resolved to build my own dock, and bought the pogo pins, but have never used them!
Even if there isn't a way the change the chips behaviour, i was wondering if there was another workaround on the kernel/software side, as i am certainly up for the job, even though not very able as a developer, and always needing to be pointed in the right direction.

[Q] How to use the Note without a Battery?

Right I am sick of seeing Samsung Battery's die, not the other day I saw at lest 5 note battery's in one of these recycle battery bins and all of them was ballooned just like mine, I want to use the device without a battery this phone is used as a home entertainment device and 3G modem nothing more, its not used as a phone any more, I want to integrate it in to my Bluetooth speaker would look nice and fit very well.
Problem is I have no idea how to go about doing this without the battery, if there a way to to trick the phone to thing it has a battery or has anyone made a factory cable for the Note?
I feel all companies that make these device to run off a battery only are destroying our world faster as there is so much life left in old android devices if we just could power them from mains power only.
I would like to power it from the battery side if I could so I can still use the USB host but this is not 100% important the 11 gig free on the device and the sd slot will do our home music needs.
Any advice would be great but please don't reply 'get a new battery there cheap', the unit once built wont have access to the battery so making it impossible to keep changing the battery when it balloons again.
Thanks, Rex

62 9262248
i think u disrespect our device,
no one accept that

darkangel0077 said:
i think u disrespect our device,
no one accept that
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Click to collapse
For a member with only 5 posts you clearly have no idea what your talking about, how is wanting to give my device a new lease of life
disrespectful? The only thing letting the device down right now is the lag of battery well damaged balloon battery, Housing this with my 50 wat
bluetooth powered speaker would really give new life to this device and how I am using it as a 3G modem I would also like to use the USB host
that this device supports.
I think you should be less disrespectful in your posts next time.
# Back to Topic
I could use wifi to access content on my network but I was hoping to set up RPI to send the phone to the TV making the device able to also stream my videos to the TV, I am not sure that Android or this device could support multi wifi connections if it could I could do that and also have a dedicated stream for my netflix.
If I can find a way to power all this then I think I will also open a build log post later with all the parts and steps
I was going to use our Acer Iconia Windows 8.1 tablet but the USB host on that is like a wet fist out of water, the android is much better at this task then the tablet.
Recap, I would like to power the device without a battery but via the battery pins so I can still use the USB host.
I need to be able to draw enough power for the device, the USB and Wifi + Bluetooth at the same time.
If any ideas on how this could be done it would be great, I was thinking using some kind of meter to find out what the battery gives the battery circet and then find some kind of multi power block to offer that.

rexzooly said:
For a member with only 5 posts you clearly have no idea what your talking about, how is wanting to give my device a new lease of life
disrespectful? The only thing letting the device down right now is the lag of battery well damaged balloon battery, Housing this with my 50 wat
bluetooth powered speaker would really give new life to this device and how I am using it as a 3G modem I would also like to use the USB host
that this device supports.
I think you should be less disrespectful in your posts next time.
# Back to Topic
I could use wifi to access content on my network but I was hoping to set up RPI to send the phone to the TV making the device able to also stream my videos to the TV, I am not sure that Android or this device could support multi wifi connections if it could I could do that and also have a dedicated stream for my netflix.
If I can find a way to power all this then I think I will also open a build log post later with all the parts and steps
I was going to use our Acer Iconia Windows 8.1 tablet but the USB host on that is like a wet fist out of water, the android is much better at this task then the tablet.
Recap, I would like to power the device without a battery but via the battery pins so I can still use the USB host.
I need to be able to draw enough power for the device, the USB and Wifi + Bluetooth at the same time.
If any ideas on how this could be done it would be great, I was thinking using some kind of meter to find out what the battery gives the battery circet and then find some kind of multi power block to offer that.
Click to expand...
Click to collapse
No Android doesn't support Multi-Wi-Fi Connections. (Don't think anything supports that...)
I've tried using Note 2 without charger, doesn't work, probably doesn't for Note either. Though it might work with a socket that supplies loads of power.
Smack that Thanks button if I helped!
KitKat came in on my OmniROM, running on my Note 2.
Sent from a small country called Singapore.
P.S. Time for school, not much time for XDA

Irwenzhao said:
I've tried using Note 2 without charger, doesn't work, probably doesn't for Note either.
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Click to collapse
Yes by default almost all phones don't let your power them on without the battery, but many newer android devices can be powered
by outlet power when in been programmed a factory mode, this is what I am asking people about if anyone has taken the chip of the batter
and provided it outlet power to fool the phone in to thinking its on battery.

You could cheat, find a power adapter and connect it to the battery connectors.

In case OP is still interested I have an idea about this issue. I had exactly the same question, how to power up an android phone without a batery plugged in.
Ignore daedric's post. Smartphones are powered by batteries which, when fully charged, provide 4.2 volts. Power adapter's output is 5 volts, so you would most probably damage your device. Supposing that phone chargers' output was 4.2 volts you would still not be able to use the device because the device draws a lot more current than a charger can provide.
My idea is to use a reliable DC-DC step down converter, and a powerful power adapter. I don't know how much current a Note could draw from its battery but I would try to find a step down converter that could at least handle 3 amps of output without damaging itself. Then I would try to find a reliable power supply like a 12v 2A. The idea is to connect the power supply to the step down converter and the converter to the battery pins on the device. Of course you would also have to set the potentiometer of the converter to output 4.2v.
BUT, there is one more problem. You have to trick the device to make it "think" that there is a battery connected and I don't know exactly how this can be done. I found on the internet a blog where a guy did so by connecting a resistor between the negative battery pin (on the device) with the third pin on the device. So, I don't know if it's possible on the Note, and how to do it. All I'm trying to say is that it might be possible, it just needs more research.

_purple_ said:
In case OP is still interested I have an idea about this issue. I had exactly the same question, how to power up an android phone without a batery plugged in.
Ignore daedric's post. Smartphones are powered by batteries which, when fully charged, provide 4.2 volts. Power adapter's output is 5 volts, so you would most probably damage your device. Supposing that phone chargers' output was 4.2 volts you would still not be able to use the device because the device draws a lot more current than a charger can provide.
My idea is to use a reliable DC-DC step down converter, and a powerful power adapter. I don't know how much current a Note could draw from its battery but I would try to find a step down converter that could at least handle 3 amps of output without damaging itself. Then I would try to find a reliable power supply like a 12v 2A. The idea is to connect the power supply to the step down converter and the converter to the battery pins on the device. Of course you would also have to set the potentiometer of the converter to output 4.2v.
BUT, there is one more problem. You have to trick the device to make it "think" that there is a battery connected and I don't know exactly how this can be done. I found on the internet a blog where a guy did so by connecting a resistor between the negative battery pin (on the device) with the third pin on the device. So, I don't know if it's possible on the Note, and how to do it. All I'm trying to say is that it might be possible, it just needs more research.
Click to expand...
Click to collapse
I was thinking maybe you could take the bust battery and like you said use some kind of step down and psu connected to the battery side of the battery's chip thing so that it would provide the right power to the device.

rexzooly said:
I was thinking maybe you could take the bust battery and like you said use some kind of step down and psu connected to the battery side of the battery's chip thing so that it would provide the right power to the device.
Click to expand...
Click to collapse
That's a very clever idea. Unfortunately, I don't have currently any old smartphone to try it. In case you try it, be cautious not to short the lithium battery. They can be very dangerous. In case it vents, the gases are very dangerous if inhaled. There's also the risk of fire.

Force slow (500mA) charging

Hey folks,
you are reading right: For a certain reason* (if you care, pls scroll down) I need to "limit" the charging current to something like 500mA.
I am running stock rom (20c, rooted) but if there are solutions for custom roms / kernels I'd give it a try.
1st thought: The phone has an inbuilt "Thermal Protect" which can be disabled via hidden menu. It seems that the file (/sys/devices/platform/lge-battery/power_supply/battery/temp_control) only accepts the values "164" and "0". I'm looking for a way to actualy lower the temperature to trick the phone into thinking "wow, battery is too hot, I'll better charge slowly"
There are also a bunch of temp throttling files in /d/tegra_thermal, but as I unterstood they do only throttle the tegra chip which I don't want.
2nd thought: I've read articles about building special cables where the usb data ports are short wired, which then is interpreted by the phone as "charge only" and draws as much current as possible. I'd need it other way round and tried to just physically block the data ports but no success.
Why am I trying this? I bought a lamp for my bicycle which has a small (150mA) battery and a usb-out. The dynamo (generator) will charge the (inbuilt) battery like up to 40%, then the lamp will activate the usb port. The phone will then charge quickly (~1A) until the battery inside the lamp will go below the threshold, and the usb port will be deactivated.. and it starts all over. I'm ending up with a few hundred charging connections/disconnections a day of cycling with actually pretty few breaks. Thanks to snoozy it's not that bad.. but it still sucks.
Any ideas appreciated, hardware and software vise.
Regards, kugelz

I guess you mean 150mAh battery.
It's interesting how you say the phone gets about 1A during charging. How do you know that? One would think this kind of USB port (driven by a small battery and a dynamo) would provide max the standard 500mA (which is the slow charging you want).
Anyway, you could try the cheapest sh*tiest USB cable you can find, since the reason for being cheap is having a thin cable, and a thin cable means less current can flow.

Iodak
You are right, 150mAh is what I meant.
Someone created a diagramm for serveral similar devices (speed / power) and for speeds > 15km/h the current is about 800mA.
I flashed iodak kernel as it has the fast charge mod, but unfortunately in the latest ready-to-flash iodak kernel (v10) there is not the latest fast_charge mod included (where you can actually specify the current) but an older version where you can only switch it on or off