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Guys, I'm hoping someone familiar with LiPo battery charging can give me some insight. I've done some diagnostics, and I'd like your take...
- Nexus 7 3G, purchased a few weeks ago. 4.2.1, not rooted, stock charger and cable
- Battery life seems good, fully charges and discharges 'normally'
- I usually charge with the device powered off (ie: blocky battery icon in the middle of the screen).
However....
- On two occasions now, I've left it on the charger for a long time (>15 hours) and have come back to a dead device.
- Pressing the power button doesn't bring up the blocky battery icon.
- Holding the power button for 30+ seconds brings the device back back.
- It has otherwise never failed to boot properly during normal use.
Out of curiosity, I was wondering if there was something wrong with the charging process causing this, so
- I plugged the stock charger into my Kill-A-Watt last night to monitor the charging current.
- Even 8 hours after the device finished charging (via the blocky icon), the current never dropped to zero - it stuck around 10mA on the AC side (ie: ~1.2W).
- My first N7 (sent back for a bad speaker and dead pixels) went to zero after charging. My iPad does the same.
QUESTION(S):
I know modern LiPo batteries have internal circuitry to prevent overcharging, but does it sound like that circuitry might be defective on mine such that I should be worried about overcharging? Could that be the reason for my lockups?
I really don't want to go through the return process again if I don't have to. I'd rather just live with it if I can prevent damage by taking it off the charger when complete. Thoughts? Opinions? Have any of you done this test, and if so, does yours go to zero?
Thanks for any insight!
developer_john said:
However....
- On two occasions now, I've left it on the charger for a long time (>15 hours) and have come back to a dead device.
- Pressing the power button doesn't bring up the blocky battery icon.
- Holding the power button for 30+ seconds brings the device back back.
- It has otherwise never failed to boot properly during normal use.
Click to expand...
Click to collapse
That might be a possible cause... Leaving any device plugged in the charger for long periods of time is not recommended. Anyway have you tried charging the tablet with another charger with a higher output? If it refuses to turn on even after holding the power button for 30 seconds you might be able to "wake" it up by using a higher output charger. Thats what I did on my Nexus 7 when the battery level went too low.
cr0wnest said:
That might be a possible cause... Leaving any device plugged in the charger for long periods of time is not recommended. Anyway have you tried charging the tablet with another charger with a higher output? If it refuses to turn on even after holding the power button for 30 seconds you might be able to "wake" it up by using a higher output charger. Thats what I did on my Nexus 7 when the battery level went too low.
Click to expand...
Click to collapse
Hmmm...everything I've read has indicated that Lithium Ion/Polymer batteries can be left on a charger without damage since they have internal circuitry to prevent overcharging (although I realize a constant topping off is probably not wise in the long run). As for a charger with a higher output, I thought the stock charger was 2.1A....I've never heard of a 3A or 4A USB charger. Can you clarify what you mean?
Also, as I said, on the two occasions it has locked up, holding the power button has brought it back, so I'm not really asking about how to get it back if it locks up - I'm asking if the behavior (locking up, charge current not dropping to 0) is indicative of a battery that has faulty overcharge protection.
Thanks though!
The "charger" IC inside the N7 not only charges the battery but at the same time powers the device - it should allow use of a N7 with no or a faulty battery. I've never looked at the standby settings on the N7 but I would suggest that is where your 1W is going. The only info about the IC I know is http://www.summitmicro.com/prod_select/summary/SMB347/SMB347.htm
Added I think this is an identical TI version of the chip http://www.ti.com/lit/ds/slusaw5a/slusaw5a.pdf
peterk-1 said:
The "charger" IC inside the N7 not only charges the battery but at the same time powers the device - it should allow use of a N7 with no or a faulty battery. I've never looked at the standby settings on the N7 but I would suggest that is where your 1W is going. The only info about the IC I know is http://www.summitmicro.com/prod_select/summary/SMB347/SMB347.htm
Added I think this is an identical TI version of the chip http://www.ti.com/lit/ds/slusaw5a/slusaw5a.pdf
Click to expand...
Click to collapse
Thanks - that's good info. However, since I have been charging with the device off, it would seem to me that it shouldn't be drawing any standby current...unless just the act of charging puts the unit in a form of standby. It also still doesn't explain why my first unit went to 0A a while after charging completed, while this one doesn't. I'm now wondering if I may be looking at roundoff error. The resolution of the kill-a-watt is .01A - which is what I'm seeing. It could just be that both units drew some current after charge completion, but this one pulls marginally more.
So, my question still stands. Does anyone familiar with LiPo technology know if this sounds like my overcharge protection circuitry is faulty? Is it normal for a device that has completed charging to draw SOME current, and if so, how much? Would someone else with a Kill-A-Watt be willing to try this and let me know what you see?
Thanks again for the help guys...
Just in case anyone is still following this thread, I have some new info. I charged my N7 last night POWERED ON.....and after charging was complete, the AC current draw went to 0A. I'm starting to wonder now whether the 1.2W constant power I saw when charging powered off is the power needed to keep the charging circuitry alive while the tablet is powered off. When the device is powered on, maybe this circuitry is running off the battery allowing the AC draw to go to 0A. I have absolutely nothing to support this, so it's just a guess/hypothesis, but at least I know my N7 is behaving the same as my first one. I also loaded Simple Battery Logger while doing my last charge and all looks normal....it charged up to about 4.208V, indicated 'full', then the voltage start dropping off - which tells me that it stopped charging. It also maintained a temp of about 23C throughout the process. I'm running a battery test right now and it doesn't seem to have been damaged by my overnight charging episodes...if anything, the battery life is better than when I first got it.
I'm going to let it go here and assume all is well. If anyone does any experiments with theirs, I'd be interested in seeing the results.
Thanks again!
As of last night my A500 will not charge. I left the device overnight and unfortunately now have Zero charge.
- My charger makes a noise, I think it always did, so I'm assuming the charger is OK.
Can anyone confirm that the chargers give off a kind of electrical buzz when working?
- I get no light at all on my A500. If the charger is OK I'm thinking something has gone within the tab, be that circuit or battery.
Any ideas or tips here?
- Sadly I do not have a multi-meter to test either the charger or the tab, no friends with a similar device, I've lost my proof or purchase (which is painful and rules out warranty), and am a bit stuck what to do.
Any ideas?
- I've heard/read that allowing the power to drop too low can cause a problem. Obviously Zero is bad in this case.
Can anyone confirm this rumour or suggest a fix?
- I did try entering recovery and resetting the battery stats - whether this made things worse or not is unclear - it certainly did not help.
ANY HELP OR IDEAS WELCOME (bear in mind that I have spent quite some time searching and trying other peoples' ideas already though.
Thanks,
ta-wan said:
As of last night my A500 will not charge. I left the device overnight and unfortunately now have Zero charge.
- My charger makes a noise, I think it always did, so I'm assuming the charger is OK.
Can anyone confirm that the chargers give off a kind of electrical buzz when working?
- I get no light at all on my A500. If the charger is OK I'm thinking something has gone within the tab, be that circuit or battery.
Any ideas or tips here?
- Sadly I do not have a multi-meter to test either the charger or the tab, no friends with a similar device, I've lost my proof or purchase (which is painful and rules out warranty), and am a bit stuck what to do.
Any ideas?
- I've heard/read that allowing the power to drop too low can cause a problem. Obviously Zero is bad in this case. Y
Can anyone confirm this rumour or suggest a fix?
- I did try entering recovery and resetting the battery stats - whether this made things worse or not is unclear - it certainly did not help.
ANY HELP OR IDEAS WELCOME (bear in mind that I have spent quite some time searching and trying other peoples' ideas already though.
Thanks,
Click to expand...
Click to collapse
Quit guessing and get the charger checked
In reply to myself and to help those with a similar issue.
Yes a charger my buzz when good OR bad. The trick to seeing whether it is working or not (aside from it charging the pad) is to see if it gets warm -- no warmth, probably broken.
As for measuring with a multimeter the trick is to insert a paper clip into the small hole in the plug and measure the voltage between the outer plug (negative) and the paperclip (linked to the positive). Few multimeters have pins that will fit inside the super tiny plug on the A500 charger so the paperclip is your way in - obviously be sure not to short circuit the thing!
There are many chargers available out there. In Australia Jay-Car and **** Smith both have perfect chargers, the correct type, voltage, amps etc, they even come with multiple pins -- sadly none fit the A500!
My solution was to go to Infinity who are a provider of Acer spare parts. They have the correct charger and are easy to deal with BUT -- It's not cheap! They want $40 for the charger and a further $30 for the little bit on the end that gives the plug its nationality. In most cases we do not need this though as we can reuse our old one, but hey, not cheap all the same.
Still, it works and I'd rather be ripped off than get the wrong thing and blow the mother board.
NOTE: if you do get a charger from anyone other than Acer or a supplier of theirs - be sure to match every detail of your current charger - especially polarity.
I had problems with charging on my A500. When I plugged in the charger the power button would turn orange for a few seconds and then start flashing white.
I took the back cover off and found that the wire to the centre pin of the power connector on the tablet had almost broken off. I touched it lightly and it came away. Re-soldering the wire fixed the problem, it now charges as expected.
After fixing it I measured the charge current. It starts at a small value for a few seconds and then jumps to full charge rate. It seems there was enough of a connection to handle the small current but as soon as it switched to full charge current the voltage drop across the remains of the connection was too much and charging stopped.
Charging problem
I too just experienced the no charging problem. I looked up how to open up the tablet and tried to trouble shoot the problem myself. My problem turned out to be a very easy fix. The Posative lead on the back of the charger port had come loose, a simple touch of the soldering iron and its fixed. I thought since I had it open I might as well go ahead and change the battery too since it was 4 years old. Its an old tablet and time to turn it into a hand me down for a lucky niece or nephew
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 ?
Hello,
I need help with my new tablet.
Model is Allfine Fine10 Yoy.
Specs:
Rockchip RK3066, 1.6GHz, Cortex A9 dual core; GPU: Mali 400 MP4
Android 4.1
1GB (DDR3)
16GB Nand Flash
10.1 Inch / IPS
Battery: 7800mAh
It is not so old, about 5 months. Few days ago I have left it to charge overnight (it usually takes 4-5 hours to charge so I always charge it overnight) and in the morning it could not turn on. It is dead, no signs of life. I checked maybe it did not charge, so I changed power socket and tried again.
I can not charge it via USB so I can't test that.
There is not sign of life when connected to PC, adb list's no devices.
There is no sign of life after holding power/lock button for a long time and there is not signs after holding restart button.
It came factory rooted, I've never updated/flashed or anything.
I have not noticed any troubles so far, no lags, no freezing, no overheating.
Are you familiar with debug method for this kind of tablet?
What should I do, what test to make?
Can you help me debug this, please.
Thank you.
cheap china tablets are easy to open up. just pry the back cover off carefully and put a volt meter on the battery. its probably dead.
check your power supply first, it might have croaked too.
Would it be possible to run tablet with removed battery, straight off adapter to check is it working?
mrnjau said:
Would it be possible to run tablet with removed battery, straight off adapter to check is it working?
Click to expand...
Click to collapse
Possibly, at least some part of startup.
Most device processors will start up if they notice power coming from somewhere.
At some point try will try to access the state and source of power.
If they notices that the battery is really dead (that is, the power is only from USB) they will shut down and go into charge-only mode.
It may be more likely that your battery is charged and the processor got wedged somehow.
Disconnect from USB, open the back, disconnect the battery and reconnect it.
Renate NST said:
Possibly, at least some part of startup.
Most device processors will start up if they notice power coming from somewhere.
At some point try will try to access the state and source of power.
If they notices that the battery is really dead (that is, the power is only from USB) they will shut down and go into charge-only mode.
It may be more likely that your battery is charged and the processor got wedged somehow.
Disconnect from USB, open the back, disconnect the battery and reconnect it.
Click to expand...
Click to collapse
Thank you for your reply,
I've precedeed as you sugested.
Solder is pretty hard on battery connection, so I unsoldered just one (negative wire, red one) and pluged it to charger and try to start it. I undsolderd just one because I don't want heat to ruin something and I guessed it should be enough to try this.
It still shows no signs of life.
However I've noticed something, when re-soldering red wire I have noticed that there is a spark when wire is near the solder point. So, there is some power in battery.
Any idea how to proceed? I still don't have multimeter to test battery voltage so that will have to wait.
Thanks once again.
Oh, sorry, I thought that the battery was on a connector.
That makes life easier than soldering.
The red wire(s) are always the positive.
The black wire(s) are always the negative (ground).
Any other color wires on a battery are thermistor, id sense or communication.
Yes, finding/borrowing a voltmeter is the next step.
Renate NST said:
Oh, sorry, I thought that the battery was on a connector.
That makes life easier than soldering.
The red wire(s) are always the positive.
The black wire(s) are always the negative (ground).
Any other color wires on a battery are thermistor, id sense or communication.
Yes, finding/borrowing a voltmeter is the next step.
Click to expand...
Click to collapse
Renate, I hope you still follow this topic.
I'm sorry for 2 months without updates, I've waited for some time for parts from China.
So, what have I done so far...
1) Get multimeter.
2) Test battery.
Battery is designated as 3.7V, however output is 4.15 - 4.16 V.
I've presumed this is fine.
3) Test the charger.
Charger is designated on 5V and 3A. I've tested voltage, it is fine. However ampers dance between 0.5A and 3.5A. I've presumed that charger is faulty, so I've ordered new one. Generic 5V, 3A charger.
4) Put it back together, re-solder the battery and connect charger. Test again.
Voltage on battery connectory is same as before - 4.15V.
After 20min there is no change in battery temperature (source: my fingers), however power jack where new charger is connected is getting warm, but not too warm.
Tried to power it on, no signs of life. Tried holding restart button for forewer, no sign of life.
I'm out of ideas.
3 Amps is a heck of a charger.
Where did that come from? Is it stock?
You have a little round coaxial connector for the charging input on the tablet?
There's no reason that it should be drawing 3 amps or anything getting warm.
The battery is fully charged.
There could be a high resistance in the battery protection module so that it looks charged but can't actually supply any current when called upon.
There's a USB connector on this too?
And nothing appears when you connect a USB cable to it?
I wouldn't expect ADB, but maybe a bootloader.
Run devmgmt.msc when plugging it in and see if anything at all shows up.
Renate NST said:
3 Amps is a heck of a charger.
Where did that come from? Is it stock?
You have a little round coaxial connector for the charging input on the tablet?
There's no reason that it should be drawing 3 amps or anything getting warm.
The battery is fully charged.
There could be a high resistance in the battery protection module so that it looks charged but can't actually supply any current when called upon.
There's a USB connector on this too?
And nothing appears when you connect a USB cable to it?
I wouldn't expect ADB, but maybe a bootloader.
Run devmgmt.msc when plugging it in and see if anything at all shows up.
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Stock charger is 3A, so I bought with indetical specs. My research showed that a lot of chinese tabs use 3A chargers (Ainol Hero, etc..)
Yes, charger connector is 2.5mm "needle".
Some 30min after I posted this area around connector and speaker on motherboard got very very hot, I almost injured myself by touching it. So I've disconnected it.
No, nothing on USB. I've mentioned it in my first post, there are no signs of life on adb. Or "dmesg", which should list something even if device was bricked.
Um, are you sure that the polarity of the supply is correct?
For coaxial plugs the center is usually positive.
If it got that hot you probably have blown something.
Renate NST said:
Um, are you sure that the polarity of the supply is correct?
For coaxial plugs the center is usually positive.
If it got that hot you probably have blown something.
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http://www.amazon.com/2000mah-Adapt...6-6172141?ie=UTF8&refRID=1AED4Q5XRX7QS8JJ91Y9
This is that kind of power connector, 2.5mm. Are we talking about the same thing? Is is possible for this kind of connectors to have non-standard polarity.
Maybe nothing is blown, I would smell that. Maybe there just hi resistance somewhere along the line.
Well, if it's the same charger and it used to charge then the polarity must be ok.
Still, something is not happy.
You should have been able to get it working with just the battery.
The DC input should not be getting hot.
I can only say so much from this distance.
Renate NST said:
Well, if it's the same charger and it used to charge then the polarity must be ok.
Still, something is not happy.
You should have been able to get it working with just the battery.
The DC input should not be getting hot.
I can only say so much from this distance.
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I can't find any info on ampers and battery. I can't measure any amps coming out of battery, that's strange. I don't know much about this but should not battery put up some ampers?
Yeah, I understand that DC port should not get hot. Only 2 options.
1) Charger (the new one) is putting up too much electricity, to many amps that is.
2) There is something faulty on DC port or around it and causes too much resistance and thus heat.
Hi everyone;
I've having an interesting time with my nexus 7 (2012 wifi 32gb).
Before I left on vacation I couldn't get the thing to charge. Looking at the usb port I thought it had become to damaged to make a good connection. So while I was away I ordered a new port assembly. Installed that and still no charging.
Oh the battery cell voltage had gone down to 2.2V so it's in a sleep mode. No problem used a proper lion charger to trickle charge it back to life then further to about 3.8V.
At that point it boots up though the optimization took the charge down to 2% so couldn't do more testing but clearly it worked just fine. However the thing won't charge. Plugging it in to USB it does detect the connection but does not draw any current (as shown by a usb voltage/current monitor). It will show the charge screen, go through 3 cycles of the battery filling animation then shut off.
I check and the voltage is getting from the usb cable into the connector. I traced the ribbon cable from the IO board up to the motherboard and at the other end I also get a nice 5V reading. Clearly the connection from the USB to the device is being made no problem.
At this point I am thinking that maybe I blew the charging circuit. When I was orignally trying to get it to charge before leaving I was applying all kinds of stress to the connector to get it to charge and there was a few times where I think I shorted it (usb monitor showed >3A and the device reset).
Anybody have another theory?
At this point I can't really use it as charging the cell externally is dangerous and not convenient. At this point from what I have seen with my testing and on here if I want to use it I would have to apply 5V to the battery connector (sans battery) which I haven't tried yet.