Does it damage the Board or not?
I accidentally did connect 5v for a second or so,
it did power on, i disconnected immediately, and after that it didnt power on for several hours,
but not sure if it was because of the interruption during boot, or overvoltage.
Can somebody confirm?
(i cant use a diode for voltage reduction, its a bit complicated, i use a load sharing capable solar charger board etc)
its a nook simple touch
Yow, don't do that!
Ok, it should be able to take it, but still.
I've often fed 4V to devices which had their battery blow up.
In worst cases I've used a diode for drop, but the voltage can be pretty variable over load.
The uboot on most things will not continue if there is zero voltage on the battery.
Also, the peak current of a device can go up to 600 mA or more at times.
That kind of current often can't come in through the USB connector.
Finally, battery packs have ID connections and thermistor.
Entirely disconnecting a battery pack will often prevent booting even when voltage is present.
If you have a dead battery pack always keep the the connector, cable and tiny PCB inside.
Attach a power supply to where the naked cells used to connect to the PCB.
For wiring of the battery pack see: https://forum.xda-developers.com/showpost.php?p=42552349&postcount=5
thanks, 2 weeks ago i prepared to measure possible resistors but did a google search before, found your description...
i use the protection board with a 18650 3000mAh lithium manganese (to prevent blow (up)) etc cell and charge it externally,
which requires switching between charging the batt + powering the nook over the batt terminals,
and using the batt for powering the nook , all that while the usb keyboard is connected and in use,
this is done via relay and a really big capacitor, which works great but is a bit ghettostyle.
i tried to use another charger board with load sharing circuitry instead,
but the only easy available module requires 5v minimum input, passes this 5v to load if the ac adapter is plugged in,
if not, it passes the battery voltage to load,
so a diode(+ parallel resistor to maintain voltage drop) or LDO doesnt work because it would at least steal around 0,5 v,
which is to much reduction for the battery voltage, because the nst powers off at ~ 3,7v,
easiest would be to just let the 5v to the nook but seems no good idea.
anyways, it works with the relay
Related
Can someone verify that the Nexus 7 can operates perfectly fine with the battery removed and only powered by the USB cable? I've read some threads eluding to this, but no one has confirmed. Mine is in the dash of my car so i cant verify this myself. If someone can. that would be amazing! Thank you.
look at the thread right below yours.
Old Guy said:
look at the thread right below yours.
Click to expand...
Click to collapse
I saw that thread, i was still a bit confused as they were talking about USB DAC and other devices hooked up to me.
I want to make sure data can still be transferred from the same USB cable and such.
Yes, it's possible, but has some side-effects
Yes, it's possible to power the Nexus 7 without battery from a USB-cable, but it involves sending power directly to the battery connection inside the Nexus 7, and it seems to have some side-effects.
The battery is a one-cell lithium polymer, which has a max charge of 4.23 V. I hoped the Nexus wouldn't fry when connecting 5 V, and it has worked fine the few minutes I've tested it. No smell of burnt electronics
Here is what I did:
Tear off the tape around the battery cable. You'll see it's soldered to a pcb-board, and the two black and two red wires are soldered together. The two wires in the middle is probably some kind of data-connection to the battery. Will investigate this further later.
Then I soldered loose the cables, so I could use the battery-connector, and soldered both red and black wires to red and black wires in a USB-cable. Drilled a hole in the back-cover right below the NFC-antenna. The back-cover is filled with all sorts of antennas, so scratch carefully with a knife before drilling. Attached some pictures of the process.
Side-effects I've noticed so far:
- It thinks the battery is at 0% and not charging.
- The clock is reset when you turn off the power. But if you have internet it will update from NTP within a minute or so.
- My computer (OS X) can't detect it anymore. So I suspect it doesn't work in USB device-mode anymore, but I'm able to connect a USB-keyboard with an OTG-cable, so it seems to work in host-mode.
Does anyone else have any experience with this, or any ideas why it doesn't work in device-mode? I'm considering adding a small connector so I can use the two extra wires from the battery to the data-wires of the USB-cable (and disconnect when not in use), and then solder a USB female cable to the original battery. That way I can (hopefully) connect the Nexus 7 to my computer when needed, and possibly analyze what the two extra wires is actually used for.
I have CM for Android 4.2, and Timur's USB-rom, but it's probably not needed for this hack, and I will probably install a stock rom if I get this working properly.
Be careful, and don't blame me if you fry your Nexus (or anything else). Be sure to turn off any fast-charge hacks when the battery is disconnected.
Old Guy - look at the thread right below yours
Click to expand...
Click to collapse
Threads are sorted by last post in each thread, so it's impossible to find which one you are referring to. Do you have an url?
Theory worked
I managed to connect the Nexus 7 to my computer again
I'm considering adding a small connector so I can use the two extra wires from the battery to the data-wires of the USB-cable (and disconnect when not in use), and then solder a USB female cable to the original battery. That way I can (hopefully) connect the Nexus 7 to my computer when needed, and possibly analyze what the two extra wires is actually used for.
Click to expand...
Click to collapse
Can confirm that this works. I didn't have any small connectors, so I hot-glued one header-pin and a female connector for a header pin on the data-wires in the USB-cable. Doesn't look good, but it works
When I have it in the car, I disconnect the header-pins on the USB-cable, and connect it to an USB power-source. When I need to connect it to the computer, I connect the header-pins and connect the battery (with the female USB-cable), and a regular USB-cable to the computer.
Sorry to bring up an older thread, but it sounds like the White and Yellow wires of the battery are for data?
if so, if I applied 3.7-4.2 volts on the battery connection and then still had a 5v connection on the USB would this work?
I would like to use Timur's ROM, and have power applied when my car is off (fixed install) for deep sleep and then apply the 5v when the car is on to bring it from the deep sleep. the issues would be faking it to not charge which I am guessing would mean to set the battery input to 4.23 volts to show as being fully charged. then when key on, the 5v would take over and you would still have the 4.23 applied at the battery connection ( probably have a diode on the + side to keep from injecting voltage to that supply
Has any one completed something like this?
The problematic usb port finally gave up on my Nexus 7 (2012). I've opened up it up, connected the black and red wires from a cut usb cable to the 1st and 4th pogo pins without removing the battery. Now charging's fast and stable..
Added: Tried 5v2a charging, it doesn't melt anything.. Fully charged in just slightly over1 hour.
This thread has been great help and a motivator for wiring my Nexus 7 to do a (permanent) dash install.
I've just removed the battery and wired it to a Pico-Box X5-ATX-180 carputer PSU with an adjustable voltage converter in-between to get around 3.9 volts to the tablet. Works great, but I found another drawback.
Like mentioned in a post before me, the battery status will show 0% which I thought wouldn't be too big of a problem. However, at the moment there is an Android update (4.4.3) available and when I try to update it first tells that the battery is too low and that I should connect a charger. So I did, but then it tells me too "wait for the battery to charge sufficiently".
So for anyone reading this wanting to do the same, know that you won't be able to update Android without a battery connected.
I have attached a photo of the tablet running without a battery for those interested.
Rutjes said:
This thread has been great help and a motivator for wiring my Nexus 7 to do a (permanent) dash install.
I've just removed the battery and wired it to a Pico-Box X5-ATX-180 carputer PSU with an adjustable voltage converter in-between to get around 3.9 volts to the tablet. Works great, but I found another drawback.
Like mentioned in a post before me, the battery status will show 0% which I thought wouldn't be too big of a problem. However, at the moment there is an Android update (4.4.3) available and when I try to update it first tells that the battery is too low and that I should connect a charger. So I did, but then it tells me too "wait for the battery to charge sufficiently".
So for anyone reading this wanting to do the same, know that you won't be able to update Android without a battery connected.
I have attached a photo of the tablet running without a battery for those interested.
Click to expand...
Click to collapse
You could use the factory image to update your nexus 7. It's just a bit more work.
Rutjes said:
This thread has been great help and a motivator for wiring my Nexus 7 to do a (permanent) dash install.
I've just removed the battery and wired it to a Pico-Box X5-ATX-180 carputer PSU with an adjustable voltage converter in-between to get around 3.9 volts to the tablet. Works great, but I found another drawback.
Like mentioned in a post before me, the battery status will show 0% which I thought wouldn't be too big of a problem. However, at the moment there is an Android update (4.4.3) available and when I try to update it first tells that the battery is too low and that I should connect a charger. So I did, but then it tells me too "wait for the battery to charge sufficiently".
So for anyone reading this wanting to do the same, know that you won't be able to update Android without a battery connected.
I have attached a photo of the tablet running without a battery for those interested.
Click to expand...
Click to collapse
What did you use to get the voltage down to 3.9 volts?
the exact thread I've been searching for.
Just completed by initial installation and now troubleshooting various problems.
The biggest being this battery scenario. So from what I've read in this thread is to use a DC-DC power switcher PICO for carputers and run that to the battery leads. How is the boot time though?
I've read that with a low battery, the kernal during bootup takes longer for checks to occur?
I have an idea.....:
If we can switch 12VDC to 5VDC during switched (Key On Accesory) with a regulator.....
we should be able to do the same with a sepearate regulator to switch 12VDC to5VDC during constant (Key off) when the switch voltage is lost.
This would retain the time you mentioned gets lost. Also, how much mAh (current) do you get out of that PICO regulator to the battery leads? The TIMUR kernal for FI-mode wants 1800mAh at least. Currently I'm using a cigarette lighter DC-DC adapter that has 2 ports. (2.1A, and 1A). The Nexus 7 is currently connected to the 2.1A and my HUB is connected to the 1A.
any advice?
Thanks
rezmax said:
Just completed by initial installation and now troubleshooting various problems.
The biggest being this battery scenario. So from what I've read in this thread is to use a DC-DC power switcher PICO for carputers and run that to the battery leads. How is the boot time though?
I've read that with a low battery, the kernal during bootup takes longer for checks to occur?
I have an idea.....:
If we can switch 12VDC to 5VDC during switched (Key On Accesory) with a regulator.....
we should be able to do the same with a sepearate regulator to switch 12VDC to5VDC during constant (Key off) when the switch voltage is lost.
This would retain the time you mentioned gets lost. Also, how much mAh (current) do you get out of that PICO regulator to the battery leads? The TIMUR kernal for FI-mode wants 1800mAh at least. Currently I'm using a cigarette lighter DC-DC adapter that has 2 ports. (2.1A, and 1A). The Nexus 7 is currently connected to the 2.1A and my HUB is connected to the 1A.
any advice?
Thanks
Click to expand...
Click to collapse
Why go through all the trouble? Just snip off any USB cable and connect to the pogo pins.. This way, you can charge at pogo's speed with any wall charger and still bring your tablet anywhere.
Hi guys just wanted to report i used your trick on my nexus 7 and it worked perfectly!
I used this method to check if the problem was the battery or if the screen was dead and it turned out to be the battery!
Now i have another battery on the way from Ebay.
Thanks again good job!
Hi guys me again,
I want to update the software but it wont let me because battery is on 1% for ever.
BUT i was wondering, what would happend if i simultaneously plug in the mini usb to another usb charger?
would that create some sort of an insane weird circut and burn my tablet?
any thoughts?
thanks!
Im thinking to use the Nexus 7 in car without the original battery. Constant 4.2V from car battery via converter to nexus battery pins and using the usb with ignition to switch the tablet between sleep and normal state. One thing i would want to reuse is the temperature sensor in the Li-ion pack. Has anyone some idea if the two extra wires are directly connected to temp sensor or there is a circuit for it on the battery controller? If so how it could be reproduced so i could use this to monitor the temp in car for example or if anyone knows any usb dongles that i could use for monitoring external temp with android.
So now i hav tryed the nexus without the battery aswell. At first i applyed 5v directly to the little black battery connector. tablet worked but showed 0%. Then tryed desoldering the batteryback from the little circuit and applyed 5v to the actual battery connectors on the circuit. It shows 100% battery and works and also the temperature sensor is working. One issue is that i need to plug in the charger before connecting the circuit to the motherboard, maybe the charger im using is just too weak that cant get the voltage up or something. And another thing is that i left it plugged in for the night and now the percentage goes down slowly as it would be discharging. havent figured out why that is. Maybe someone has tackled this before also?
freakadell said:
So now i hav tryed the nexus without the battery aswell. At first i applyed 5v directly to the little black battery connector. tablet worked but showed 0%. Then tryed desoldering the batteryback from the little circuit and applyed 5v to the actual battery connectors on the circuit. It shows 100% battery and works and also the temperature sensor is working. One issue is that i need to plug in the charger before connecting the circuit to the motherboard, maybe the charger im using is just too weak that cant get the voltage up or something. And another thing is that i left it plugged in for the night and now the percentage goes down slowly as it would be discharging. havent figured out why that is. Maybe someone has tackled this before also?
Click to expand...
Click to collapse
You supplied power to the protection circuit? I'm surprised that worked.
The battery is probably going down because the protection circuit is designed to prevent over and under voltage. Since you're feeding it 5V and a lithium battery is supposed to max out at about 4.2V it must be trying to lower the voltage somehow. The percentage going down is probably nothing to worry about, but I'd strongly recommend connecting to the battery connector instead, and only connecting it like this when you need to have a certain percentage to do a system update etc. Also be careful with the bare battery, if the two pins short it could catch fire.
Hi i tried that works ,however it doesn't boot when powered i have to turn it on pressing power button,any idea why?
As a car dash its pretty useless now
Just a quick message that I have managed to power my nexus 7 2012 from a USB cable connected to the circuit board that was attached to my dead battery. Battery level indicator is permanently at 100%.
Sort of like the above it involves using the battery circuit board but it is disconnected from the battery.
Step 1: Strip back battery wrapping revealing the board attached to the connector cables (that connects to Nexus 7)
Step 2: Cut the metal strips going from the circuit board to the actual battery part
Step 3: Solder USB cable Positive wire to board pad labelled VP and Negative to pad VG(? not 100% on last one, but it's the other pad)
Step 4: Solder short wire from VP pad to other side of the board onto the ++ pad (that goes to the red wires then connector)
Step 5: Wrap board up with elec/other tape to avoid shorts
Step 6: Connect up and power on
Not sure why the last wire is needed but it didn't work for me without it.
Next step for me is to wire it to the onboard micro-usb
Where is the ++ pad ??
dribbleboy said:
Step 4: Solder short wire from VP pad to other side of the board onto the ++ pad (that goes to the red wires then connector)
Not sure why the last wire is needed but it didn't work for me without it.
Next step for me is to wire it to the onboard micro-usb
Click to expand...
Click to collapse
Where is the ++ pad mentioned in step 4 ? Can you post some pictures ?
Hi!
I bought a brand new NST on ebay, when i plugged to charger the led light up as green, dont orange. few hours later i coudnt turn on, i disassembled the nook. the battery case was torn, the voltmeter show 0,3 V, my multicharger coudnt see as a lipo battery. i bought a 3,7V 1500mAh lipo cell, i cut the "charger pcb" from the old battery, soldered to the new cell. but not working. when i plug to charger or usb the led light up green. but green without battery too. the pc show as a "omap 3630 device, but nothing too.
the new battery show :3,99V on black-red wire.
9,2 K resistance on black-yellow
99,8K resist. on the green-black with the original wiring, but nothing.
I try to solder a 10K to yellow and 30K to green resistance to ground (black) but not working this method!!! the led is green when i plug to charger with or without battery. i thing the nook cant see the battery is plugged.
can anyone measure and tell me the original battery good parameters???? yellow-black, green-black,etc. or what can i do that the nook see the battery. the original battery was LICO, china!!!!
I m live in hungary, i bought from uk, the delivery cost was 1/3 price of the nook, the re-send and re-delivery cost not return...
thanks!!!!
update: if i try to charge the battery pack via 6pin outlet with my lipo charger (red-black wire),it identify as a 3,7V lipo cell but say the "connection break" after 2 second charging. if i try to charge directly on the cell pinouts its everything ok!!!!
i cant buy a new battery in hungary now. if i soldering 10K,30K,+ and ground directly to the battery without "charging pcb" it s good idea or other solutions???
thanks
More people seem to have problems with batteries.
I'd like to see if we could get a handle on this.
Some background info:
If you plug a USB host (like a PC) into the Nook with or without a battery it should do the inital power up.
The processor finds itself powered up somehow and starts executing internal bootstrap code in ROM.
It identifies on USB as OMAP3630.
It waits around a few seconds for a command then continues.
Depending on which jumper resistors are soldered in (I'm still looking for this info),
it tries to find the primary boot loader on the SD card or the internal NAND.
The file it looks for is MLO on a FAT disk.
This file is actually x-loader, a very simple loader.
x-loader will load u-boot.bin
Here is where things get complicated.
Up until this point the processor only knows that it seems to have power.
It has not engaged enough peripherals to figure out what or how.
It's at this point that u-boot checks to see if a battery is connected,
what the temperature and voltage is.
Although from a technical point of view the Nook could boot up Android now
without a problem u-boot does not allow it.
Everybody has had that annoying situation of a dead Nook plugged into
a charger and wants to read their book but u-boot digs its heals in and says,
"No, you have to wait while I do some charging."
If you have the battery disconnected but the two sources of identification
wired around (the thermistor and the ID resistance) the Nook will try to charge.
See: http://forum.xda-developers.com/showthread.php?p=42552349#post42552349
It will pulse on and off at about a one second cycle the charging on the battery.
If you connect an LED and a 220-1000 ohm resistor between the battery connection
point and ground you should see it flashing.
If at this point you connect just for a moment the two wires of an external LiPo battery
the display should be activated and go through the charging animation.
Remove the battery and the animation will continue.
This is proof that the Nook could be happy without any battery.
So where does this leave you with your specific problem?
The first question is whether your original battery really has a problem or just discharged.
If you tore the battery apart and couldn't even charge it without the battery protection module that might be something.
Note: I am not advocating the permanent removal of the battery protection module.
I'm just saying for the purpose of testing when you have your eyes right on the battery it's ok.
Check to see if you can get the LED above to flash.
Check if your hacking resistors are correct.
You had a McNair battery pack and the ID resistance was 100K?
I was trying to get my kernel console on the Nook working but something is screwy with it right now.
I would have liked to see if some of the printf's in u-boot were saying something.
Edit:
I just realized that you reused the old BPM from the old battery.
We haven't yet ruled that out as the problem.
Try (as an experiment) using the new battery without the BPM.
Make sure that the voltage on the battery stays between 3.5 and 4.0 V
Do not permanently install anything without the BPM!
Ok,
i cut the battery pcb (protection module) from the new cell and the 6 pin outlet.
connected the wires directly to the lipo cell as follows:
2X red wire to batt +
2x black wire to batt - (ground)
yellow wire to ground via 10K resistor
green wire to ground via 30K resistor
i connected the 6pin plug to the nook and it turned on!!!!!
i do not know that i get or make other protection module for the battery. Anyone can measure the values of R and C? I do not dare to use without module via usb or charger. i can charge the battery separated from the nook, but not the best...
i dont know whats the MCNair battery pack.
on the old battery label:
Model No.:s11ND018A REV: B
LICO, made in China
and yes, the green-ground resistance is 100K on protection module.
i cant discharge the battery with my multicharger if i connect via module. (i try 0,1 and 0,5A too,not discharge)
many thanks
I have been reading all the posts regarding the dreaded "black screen" issue. However mine doesn't seem to fit the bill
It has been left to discharge and wouldn't boot up. i plugged it in (wall charger) and left it for 24hrs. I tried to boot it up but all that comes on is the Google logo then i see some white video streaks then it turns black again
It is rooted and i tried to boot into TWRP but it shows the same streaks then it turns black again. I did press on the back where the connector was supposed to be and thinking would fix it but no success
I do not know what else to do.
Do i need a new screen? I wouldn't mind to replace it if i knew that was the problem but i am not sure if that is the case
Is there anyone that had a similar experience and can maybe share some ideas?
I would really appreciate it!!
Thank you
rainfactor said:
...regarding the dreaded "black screen" issue. However mine doesn't seem to fit the bill
It has been left to discharge and wouldn't boot up.
Click to expand...
Click to collapse
I was under the impression that that scenario is exactly the bill - the battery drains off to such a low voltage that the internal charge controller circuit doesn't work correctly at that low voltage, even when you put the device back on the charger, so you are stuck with a not-dead unit that won't turn on, and also won't take a charge. (But that hardware isn't dead - you just need a partial charge on the battery to get the charge circuit to start working again.)
The only recourse really is to get a *small* amount of charge on the battery by some means other than the built in charger, and then reconnect the battery to the tablet and put it on the charger to complete the charging.
There are disassembly instructions on here that take you through the steps necessary to get to the battery connector (it detaches and has a short run of wire between that connector & the battery so that should be convenient for attaching the battery to something else without removing the battery from the tablet). Use the search functions.
If you can borrow a voltmeter, the symptom will be obvious: a very discharged battery will have a terminal voltage around 3.0v (maybe less). Under normal conditions the battery voltage will rise to about 4.05v when fully charged (measured when disconnected from the charger) and be somewhere around 3v when completely discharged.
Don't do anything stupid (there are examples of that on here too). The charger that you use needs to limit the amount of current to a reasonable value, say less than 500 mA. The battery can tolerate up to about 1.8 Amps of charging current but you should use something far more conservative than that for safety reasons. And you are only trying to put a small charge on the battery (not completely charge it) so you don't need to use the fastest possible charging rate anyway.
Something incredibly cheap would be a USB cable (with the micro-B connector cut off) and a 1/4 watt, 100 ohm resistor connected to the positive supply line coming from a 5 volt USB wall wart charger. Even if the battery was a dead short, only 50 mA of current would flow and the resistor wouldn't burn up. If the battery was good but heavily discharged, you'd only be charging at a 20 mA rate - that would put a 10% charge on the battery in ~30 hours.
If you initially measured the battery and found it had a voltage of 2.5v or higher, you could use a 22 ohm, 1/4 watt resistor safely and charge the battery 10% in only 8 hours or so.
You can charge faster by using a resistor of a higher wattage rating, but 1/4 watt size are readily available and cheap.
The equation for power dissipated in the resistor is
P > V^2/R or
R > V^2/P = (Vs- Vb)^2/P
So for example in our case with Vs = 5, Vb = 3 and a 1/4 Watt (P) resistor, we would get
R > V^2/P = (Vs- Vb)^2/P = (5-3)^2/0.25 = 16 ohms.
The "dead shorted battery" worst case would be Vb=0 or
R > (5-0)^2/0.25 = 100 ohms
(so you can see where the numbers came from)
Anyway, that's my recommendation
- disassemble to the point of exposing the battery connector
-disconnect battery from tablet
- put battery on simple & safe charging circuit (+ terminal to resistor to + terminal, and - terminal to - terminal)
- let it sit for a while*
- reconnect to tablet and finish charging
- profit
* if you leave a live circuit unattended, even if it is only a 5v circuit, please please no exposed wiring or loose connections. Use tape and plastic straws for temporary insulation... or shrink wrap if you prefer a neater look.
bftb0 said:
I was under the impression that that scenario is exactly the bill - the battery drains off to such a low voltage that the internal charge controller circuit doesn't work correctly at that low voltage, even when you put the device back on the charger, so you are stuck with a not-dead unit that won't turn on, and also won't take a charge. (But that hardware isn't dead - you just need a partial charge on the battery to get the charge circuit to start working again.)
The only recourse really is to get a *small* amount of charge on the battery by some means other than the built in charger, and then reconnect the battery to the tablet and put it on the charger to complete the charging.
There are disassembly instructions on here that take you through the steps necessary to get to the battery connector (it detaches and has a short run of wire between that connector & the battery so that should be convenient for attaching the battery to something else without removing the battery from the tablet). Use the search functions.
If you can borrow a voltmeter, the symptom will be obvious: a very discharged battery will have a terminal voltage around 3.0v (maybe less). Under normal conditions the battery voltage will rise to about 4.05v when fully charged (measured when disconnected from the charger) and be somewhere around 3v when completely discharged.
Don't do anything stupid (there are examples of that on here too). The charger that you use needs to limit the amount of current to a reasonable value, say less than 500 mA. The battery can tolerate up to about 1.8 Amps of charging current but you should use something far more conservative than that for safety reasons. And you are only trying to put a small charge on the battery (not completely charge it) so you don't need to use the fastest possible charging rate anyway.
Something incredibly cheap would be a USB cable (with the micro-B connector cut off) and a 1/4 watt, 100 ohm resistor connected to the positive supply line coming from a 5 volt USB wall wart charger. Even if the battery was a dead short, only 50 mA of current would flow and the resistor wouldn't burn up. If the battery was good but heavily discharged, you'd only be charging at a 20 mA rate - that would put a 10% charge on the battery in ~30 hours.
If you initially measured the battery and found it had a voltage of 2.5v or higher, you could use a 22 ohm, 1/4 watt resistor safely and charge the battery 10% in only 8 hours or so.
You can charge faster by using a resistor of a higher wattage rating, but 1/4 watt size are readily available and cheap.
The equation for power dissipated in the resistor is
P > V^2/R or
R > V^2/P = (Vs- Vb)^2/P
So for example in our case with Vs = 5, Vb = 3 and a 1/4 Watt (P) resistor, we would get
R > V^2/P = (Vs- Vb)^2/P = (5-3)^2/0.25 = 16 ohms.
The "dead shorted battery" worst case would be Vb=0 or
R > (5-0)^2/0.25 = 100 ohms
(so you can see where the numbers came from)
Anyway, that's my recommendation
- disassemble to the point of exposing the battery connector
-disconnect battery from tablet
- put battery on simple & safe charging circuit (+ terminal to resistor to + terminal, and - terminal to - terminal)
- let it sit for a while*
- reconnect to tablet and finish charging
- profit
* if you leave a live circuit unattended, even if it is only a 5v circuit, please please no exposed wiring or loose connections. Use tape and plastic straws for temporary insulation... or shrink wrap if you prefer a neater look.
Click to expand...
Click to collapse
Wow! THANK YOU VERY MUCH !! I did not expect such a detailed answer.
I REALLY appreciate for taking the time to answer me!
I will try the things you recommended:good::good::good:
rainfactor said:
Wow! THANK YOU VERY MUCH !! I did not expect such a detailed answer.
I REALLY appreciate for taking the time to answer me!
I will try the things you recommended:good::good::good:
Click to expand...
Click to collapse
The more information you can collect before you begin the more confidence you will have. Hopefully you have a voltmeter or can borrow one to insure you are getting the wiring polarity correct and you are not going to damage anything or cause a fire.
If the battery voltage is closer to 4v when you first crack open the device, then this hypothesis about an overly-discharged battery is not correct, and you should assume that some other mechanism is involved.
The resistor values I used as examples are just barely big enough to meet their own thermal rating (1/4 watt in the examples), so that means that they can get hot. I'm pretty sure their thermal rating is for "natural convection", meaning that you don't need to put a fan on them to keep them cool, but you shouldn't cover their bodies up with any insulation or shrink-wrap. Nor should you leave them in that state next to a pile of papers or a jug of gasoline
A more sophisticated approach would involve using an adjustable battery charger that operates near 5v (the normal wall-wart USB voltage) and will let you set the current level, but almost nobody owns one of those. (But I have plenty of dodgy USB cables that the cats have chewed on that can be sacrificed for a quick-n-dirty trickle charge exercise.)
good luck.
My android tablet suddenly died on me and refuses to power up. Unable to charge the battery as well.
Am thinking of removing the battery from the tablet and then hooking up a lipo charger to the black and red wires on the circuit board. Hopefully this can power it on directly without the battery.
This is a simple and inexpensive lipo charger I'm looking at:
www[dot]sgbotic[dot]com/index.php?dispatch=products.view&product_id=999
Few concerns that I have:
Can the lipo charger be used as a direct power supply? I know voltage-wise, it's safe (3.7V). But I'm not sure if circuitry-wise, a charger works the same way as a power supply
Is 500mA current output from the charger enough to power on the tablet? If not, what is the recommended current output?
How do I know if the tablet has any logic to detect the presence of a battery? From what I see on the circuit board, there are only 2 black+red connectors (no data connector or anything)
A proper battery should less than that $15 charger. Even if you did bypass the battery you should be able to find a less expensive power supply.
Sent from my SM-N900T using Tapatalk
Spoo76 said:
A proper battery should less than that $15 charger. Even if you did bypass the battery you should be able to find a less expensive power supply.
Sent from my SM-N900T using Tapatalk
Click to expand...
Click to collapse
It uses a 12000mAh battery, which I think cost $40-60. The thing is, I'm not sure whether the issue lies with the battery. So i thought of bypassing the battery and see if it is a circuit board problem.
Here's the "tablet" I have. It's actually the viewing panel of my digital door viewer. Essentially a stripped down Android tablet:
www[dot]rollupcn.com/index.php/iHome4/show/19.html
Btw here're the pics of how the battery and the mainboard look like:
https[colon]//d3nevzfk7ii3be[dot]cloudfront.net/igi/SYJVWTdAPAPBRVCG
https[colon]//d3nevzfk7ii3be[dot]cloudfront.net/igi/q52LQk2X1s6NOaTK
Thing is - I'm not sure if the problem lies with the battery or the mainboard. Any suggestion on how to troubleshoot?
If you want to hack your Power from battery to directly input,
but fails to bypass battery check.
I have a idea that works. (some electricity knowledge required)
You can use a capacitor to "cheat" PMIC, and running on usb cable power.
Go buy a super capacitor (a 4.0F V-type should be OK.)
Charge it with the working voltage. (a few seconds is enough for that.)
Then remove your battery. Strip off the battery controller that you'll need.
Find out the positive and negative on it.(Important!)
And connect the charged super capacitor with battery controller, and put it back battery slot (It's small and fits)
And you can boot on cable power without battery!
In case you still look for a solution, I would connect a functioning Li-Ion battery, either 18650 or from another phone with at least 2000mAh capacity and hook a single cell Li-Ion charger with at least 1A rating.
Things to consider:
- the charger is likely to be noisy and needs a battery to smooth out the wave. It may or may not be an issue. Having a battery connected will dampen it down.
- connecting a smaller battery and powering the tablet via USB may dump too much current into the battery
- the tablet may draw up to 4A on boot, probably 800mA min, so your charger will need a full battery as a backup
- don't use a charger for a different battery chemistry. There is a chance of damage or even fire.
- some devices use I2C interface to talk to the BMS, but this is unlikely in your case
- make sure the temp battery you are using has a BMS
Hi,
i use a Nook Simple Touch as typewriter with an usb-keyboard,
which works great thanks to the usb host mode app, or, automated:
an old version of tasker with a plugin to deactivate charging and activate hostmode ( and fastmode...) via shell command after booting.
The problem is, this mode drains the battery really fast,
and charging while using the keyboard, so nececessarily with OTG cable attached, is a bit of a pain in the neck,
because there is only 1 possible sequence of actions how you can enable charging with more than around 100 mA (which would be way too low in this case) while the keyboard is active,
which requires a 16k resistor between GND and ID pin, rebooting, temporarily disconnecting some wires via switch, tapping around etc etc,
(and also does not work well when the nook is completely off ),
so i decided to leave the usb port exclusively for the keyboard,
an remove the internal battery an replace it with a external big 7000mAh or so 1S li-ion pack,
which is charged externally with a lipo module
(while charging, the nook is powered by an ac adapter, power source switching is realised with a relay and a really big capactior to avoid any more complicated possibly failing electronics)
which works great and is very easy to handle,
BUT i really dont like li-ion batterys of any kind because of the fire hazard,
nimh eneloop cant be used because charging in parallel is not a good idea,
so i would like to use lifepo4 chemistry instead,
which has a working woltage between around 3 and 3,6 volts,
but the nook powers down at around 3,65 volts.
A boost/buck converter isnt possible because as the battery drains, the voltage must sink slowly for the nook to make a normal shutdown
and not crash, damage the file system etc, (and also a converter drains quite much battery even if the nook is completely off.)
Question: it would be VERY kind if anyone who has a clue about this could share his opionion on that:
is it possible (if the hardware itself can handle it) to lower the android/nook shutdown voltage to about 3 volts with some rom/software modifications ?
threshold not treshold
Wow, this all seems a bit complicated.
I had never heard of this 16K resistor stuff.
As far as I could tell, the ID pin is only sensed high or low..
Unless I'm mistaken the OMAP3621 ULPI registers only indicate high/low.
The TPS65921B (which is the actual PHY) list 90K as the typical break point.
Of course, there could be a circuit completely external to the ULPI/PHY.
Where did you find out about 16K?
Changing the voltage of everything seems the difficult way to go.
You'd have to modify uboot as well as the charger daemon.
A note: The USB charge pump is pretty inefficient, 55%.
If you were to load the USB to the maximum speced 100mA with a 3V battery, it would be drawing 303mA from the battery!
5V × 100mA / 3v / 55% = 303mA
Oh, you got me confused with your two posts.
When you were talking about ID and 16K did you mean the ID on the battery pack or the ID on the USB OTG?
Renate NST said:
Where did you find out about 16K?
Click to expand...
Click to collapse
wired a 50k pot between gnd and id pin,
in the usb mode app tapped "host" and watched if the led goes an stays on,
if not, lowered the resistance, tried again etc,
as soon it stayed on (at 16k at my device ) used this value as permanent fixed resistor.
with that otg mode keyboard use is possible,
but also at the same time the nook doesnt really believe its in otg mode so charging with 500mA is possible,
if done in this order:
- feed 5v to the + - of the usb cable
- reboot (not always required)
- remove an reinsert usb plug
- hit "host" 2 times, keyboard works and charging with around 500mA works (measured it)
but charging doesnt work when nst ist powered off,
and automount of the keyboard at startup via shell is not possible,
and cable acrobatic is required,
and as you say, usb charging is inefficient.
the other solution with an external battery (at the nst batt terminals) with external charging logic with a relay is a much easyer way,
but depends on a li-ion cell because of the 3,7-4,2 voltages the nook can use,
a lifepo4 ( or 2s li titanate + diode) would be safer and has more cycles but would require the nook
to work with 3 to 3,7 volts, which seems too complicated, changing demons etc whatever that is...
after some research it seems its not really an issue, the newer sanyo/panasonic, samsung, sony, lg powertool/ebike cells seem to be quite safe, as far as youtube shortcircuit etc tests demonstrate.
thanks for the orientational infos
Renate NST said:
Oh, you got me confused with your two posts.
When you were talking about ID and 16K did you mean the ID on the battery pack or the ID on the USB OTG?
Click to expand...
Click to collapse
sorry, i should have used one thread, i suggest ignoring the other one,
where the only request was if the nook battery terminals can survive up to 5v,
here was the request if the nook can be modified to accept at the battery terminals a voltage down to 3v and stay on.
so 3v too complicated, 5v too dangerous,
so i stick with the relay and the li-ion cell, no problem, i was just curious if an improvement would be easily possible.
the battery id resistors have nothing to to with all that, 10k and 30k work fine,
i meant the 5 pin micro usb otg connector, not shorted zero ohms as usual, but 16k.
(but thats obsolete now)
another observation: in some thread you mention you charge the nook while using an usb keyboard,
i tested it and with a normal otg cable, and the usb mode app set to 500 mA oder 1,5 A,
and a 50% charged normal internal battery,
the device draws around 250mA, and the battery gets charged very slowly, or not at all, depending on cpu usage etc.
and if the battery reaches 100% , it continues to draw around 250 mA, which is strange,
because when using a normal, non-otg usb cable,
the device draw only around 100mA when the battery had reached 100%,
so the difference must be used for heating purposes somewhere or overcharge the battery,
which might be a reason for swelling lipos.