yashsingh1/xdaforums huggingface dataset:
[Nexus 7 Q&A, Help & Troubleshooting] najaboy:
Two of the ”fixes” that folks anecdotally reported... using a battery calibration app and clearing battery stats are 100% guaranteed not to work. Those who actually ascribe any effect to them are merely using faulty reasoning. Quite simply, the calibration apps are just another method of wiping battery stats. Nothing at all in batterystats.bin has any bearing on battery life or reported charge indication.

This isn't directed at anyone in particular. Rather, I'm just expounding on something from the OP.

Definitely a very useful thread, given what seems to be a not too uncommon issue. As an aside, I've also experienced the problem after flashing a new kernel. Reflashing the previous kernel corrected the issue.
[Nexus 7 Q&A, Help & Troubleshooting] billykxda:
najaboy:

Excellent background on those two "fixes", and I agree 100%.

In creating this thread, I didn't want to really slam-dunk any of the "fixes" that other people have offered in other threads. But the research shows that you are exactly right: calibration apps and wiping battery stats will do absolutely nothing - guaranteed.

It's amazing how many misleading threads I had to wade-through to get to the fixes I recommend. No wonder so many people have returned their N7's to get one that "doesn't have the issues". ;)
[Nexus 7 Q&A, Help & Troubleshooting] Hazmatilda:
Crisis averted

Brand new Nexus 7 purchased today, came with 4.1 and I applied 4.2.1. Difficulties getting it powered on in the first place and lots of reboots and apparent crashes. Factory reset once and found some of those other threads you mentioned, disabled location services and that seemed to help a bit but still getting reboots. More digging and I found your post. Took your advice and pulled off the back of the Nexus 7, pulled the battery up and the connector basically fell out, it obviously wasn't seeded properly. Popped it back in properly and it's working much better now, although I'm going to give it 24 hours to make sure my issues are resolved. I just created an account in here to thank you. Think I'll stick around and see what else I can learn.
[Nexus 7 Q&A, Help & Troubleshooting] webslasher:
got my nexus 7 at September 2012,

got no problem with the abttery at the first charge,

but few weeks later, the battery started to die at 20% , then died at 30%, i didnt notice until i saw the battery history, it just jumped from 30% to 0%,

keep in mind that i'm not using the asus standard charger (dont know if this affect us)

tried charging it with the original charger, look like the problem is fixed, the battery died at 5%.

not sure if this is a coincidence or not

sorry for the bad English
[Nexus 7 Q&A, Help & Troubleshooting] billykxda:
Congrats!

Go enjoy your new N7!
[Nexus 7 Q&A, Help & Troubleshooting] billykxda:
Have you tried the recommendations in the op?
[Nexus 7 Q&A, Help & Troubleshooting] billykxda:
I guess you solved your issue?
[Nexus 7 Q&A, Help & Troubleshooting] Fotogravin:
Re: N7 Turns Off/Won't Turn Back On - A Summary...

I did have issue #2. I already had fully charged over night. Battery indicator showed 100% for a while, so I figured the problem wasn't solved. What I did was shut down my N7, then hook it up to the charger, boot my N7, unhooked it from charger, played 1 level in Amazing Alex and checked battery indicator again: 99%. I hope this means I solved the problem for now

Verstuurd van mijn Nexus 7 met Tapatalk
[Nexus 7 Q&A, Help & Troubleshooting] billykxda:
Interesting. There have been reports of people addressing this problem by just turning off their N7 for a while, booting back up and all is well. Others like you added the plug/unplug charger to the mix and that seemed to work for them.

This issue has been reported to Google as well - there is a thread on Googles defect site that also lists all sorts of "fixes" that people have attributed to this issue.

Still, the only highly-repeatable fixes I've seen in various threads/forums are in the OP. But, who knows? If you can get your N7 past these issues, it's a good thing!
[Nexus 7 Q&A, Help & Troubleshooting] roswell782:
Re: N7 Turns Off/Won't Turn Back On - A Summary...

Hi, you can add me to the list. My N7 often turn off itself when battery level is under 50%. I have tried everything (factory reset, flash stock image...) but problem still persists.

So i have a N7 with half battery capacity most of the time. I hope next update will fix it otherwise i'll send it to Asus.

Edit: mine just switch off at nearly 25%, i'll try to downgrade to 4.1.2 and see if it helps...
[Nexus 7 Q&A, Help & Troubleshooting] billykxda:
Hi!

Did you try all of the suggestions in the OP?

-bk
[Nexus 7 Q&A, Help & Troubleshooting] roswell782:
Re: N7 Turns Off/Won't Turn Back On - A Summary...

Hi, i didn't open the battery cover because i don't want to lose my warranty, i prefer to let Asus do it for me.

My history with Asus is finished, bought 3 products from them, 3 have problems...

Btw: of course downgrade to 4.1.2 did nothing ;)

Thanks for your answer and have a good weekend.

Cheers, Ros.

Edit: RMA asked, hope Asus will fix it.
[Nexus 7 Q&A, Help & Troubleshooting] ynrozturk:
My N7 is driving me crazy. Bought it last year around October, and it seemed fine at first. Battery would die at around 4-5% which is acceptable. Then it started getting worse over time. At this time it was completely stock - locked and not rooted. It got to the point where it would shut itself off when it reached 40%, so I decided to factory reset, pull battery, unlock, root and install Paranoid Android, hoping this would solve (or help) the issue.

Did all my unlocking and rooting last night, installed PA, set everything up, then started reading on my N7. Device turned off at 65% now. To say that I'm disappointed is an understatement. I'm all out of ideas on what I can do to fix this thing. I charged it overnight and disconnected it from the charger 3 hours ago, and it's still at 100%, even though I've used it quite a bit. Infuriating.
[Nexus 7 Q&A, Help & Troubleshooting] billykxda:
Sorry to hear this. This is what I'd recommend...

Take the N7 back to bone stock to reduce the number of variables. Follow my suggestions in the OP (I know you've already done them - but I'd still "do the drill" again). If this doesn't work, you can try some of the outlier suggestions that others have made that are less substantiated - why not at that point? If it's still a no-go, I'd return it. For your money, you deserve a perfect N7.
[Nexus 7 Q&A, Help & Troubleshooting] biondi53:
APX mode?? what is this?
[Nexus 7 Q&A, Help & Troubleshooting] Tormado:
Hey everyone, having possible brick problems with my nexus 7 (flo). After updating it to pa 4.4 kitkate v2 it shut off and went into bootloader. After that it would be stuck at bootloader everytime I tried to turn it on. Couldn't enter OS. Tried to go to TWCP recovery I had installed and same thing happened. Just rebooted into bootloader. I gave up on it for a few days now trying to get back to it now it won't even turn on/charge. Tried turning it on in any mode OS/fastboot/recovery, and nothing works. Trying to charge it but I assume it won't even charge. (just shows the empty battery icon for a second not charging e.a. not filling up and dies again). Tried to research the topic but coudn't find anything that helps.

Any suggestions are greatly appreciated. Thanks!

P.S. Have been on CFW for 4 years now from droid to gnex, so have a general knowledge in the topic.
[Nexus 7 Q&A, Help & Troubleshooting] billykxda:
Try following each "fix" in the OP. Then we'll have a baseline from which to assist you.
[Nexus 7 Q&A, Help & Troubleshooting] Tormado:
Hey Billy! thanks for swift response! Will try to do them during lunch break and get back to you. Many thanks!

Update: worked it out. Seemed to be just the Hardware button problem. Took of the back without tinkering with wires and held the bare power button on for 30 seconds and it booted into bootloader, upon which I just followed ATGAdmin's guide on how to repair soft brick on nexus 7 flo.

Thanks for the guide Billyd!
[Nexus 7 Q&A, Help & Troubleshooting] Alvinushka:
erased bootloader an I can't turn on or enter in bootloader. Can someone help me?
[Nexus 7 Q&A, Help & Troubleshooting] billykxda:
Try posting out outside of this thread, as it's not really focused on bootloader issues.

You'll probably get a bunch of quick responses.

Good luck!
[Nexus 7 Q&A, Help & Troubleshooting] draggehn:
Thank you! I've been having problem #1 and hopefully this will help. I'll try the solution later today and will edit this post with the results.

Thanks again!
[Nexus 7 Q&A, Help & Troubleshooting] drenze:
Nothing working...

I'm having issue #3 with my wife's N7. She keeps flatlining the battery, this is now the 3rd or 4th time I've had the issue with it not wanting to turn back on. Every other time, I've been able to boot to the bootloader and take care of the issue, but this time she's not wanting to. I've even gone as far as to disconnect the battery this time and leaving it sit for awhile, then plugging back in and attempting to restart...nothing.

Oddly enough, I tend to flatline my N7 about once a week, yet I've never had an issue with it not wanting to restart. But then, I've long since reimaged mine with Cyanogenmod (don't know whether that has anything to do with it).

Suggestions?

Thanks.
[Nexus 7 Q&A, Help & Troubleshooting] billykxda:
Your welcome!

Enjoy your N7!
[Nexus 7 Q&A, Help & Troubleshooting] billykxda:
Did you try all of the fixes in the OP?
[Nexus 7 Q&A, Help & Troubleshooting] drenze:
Apologies for (a) Not being clear in my original post, and (b) taking so long to get back to you.

Yes - I've tried all the fixes from the OP (within limits). Nothing I've been able to from the OP has been able to get her N7 to even respond and show ANYTHING on the screen.

To date, I have:

Disconnected/reseated the battery connector - failed to resolve.

Plugged into an original ASUS charger (the one I use for my N7) and held down the power button for up to 5 min. - failed to resolve.

Due to #2 failing to bring back any response on screen, I haven't been able to do a factory reset, go to the bootloader & do a shutdown, or anything like that.

I have also disconnected the battery and let the N7 just sit for 72+ hours without any luck.

In the past, #2, followed by going to the bootloader and doing a shutdown has ALWAYS resolved this issue for me.

Help?
[Nexus 7 Q&A, Help & Troubleshooting] billykxda:
One thing that has worked for some that wasn't in your list is plugging your N7 into your PC via USB. Have you tried that?

-bk
[Nexus 7 Q&A, Help & Troubleshooting] drenze:
Erps - yes, I have. Sorry - was going down the list from the OP. I'm starting to worry that the N7 is bricked, but I don't know how that's possible, as it was working just fine before the battery flatlined.

I've even tried (while plugged into the PC) to see whether ADB would recognize it, to see if I could boot to bootloader from ADB. It didn't. :(
[Nexus 7 Q&A, Help & Troubleshooting] chrisbo4:
My wife's N7 failed to boot after my 5 year old ran the battery down to 0%. I tried pretty much everything you tried, and the only thing to bring it back was a factory reset. Hope you get it figured out.
[Nexus 7 Q&A, Help & Troubleshooting] billykxda:
Sorry to hear this. If you've exhausted all of the fixes in the OP, you may be looking at needing to return it.
[Nexus 7 Q&A, Help & Troubleshooting] billykxda:
Factory reset (listed under #2 in the OP) works for a good number of people.

Glad to hear that it worked for you.
[Nexus 7 Q&A, Help & Troubleshooting] chrismcnally:
My nexus 7 was also dead and would not boot after letting the battery die. So I left it plugged in for 3 days and now it comes on, but battery is at 23 percent. I suggest you plug it into a wall and leave it for at least 48 hours. Good luck
[Nexus 7 Q&A, Help & Troubleshooting] ironmaskusa:
Yea, I woke up this morning and found my N7 in the floor beside my bed. I usually leave it on the night stand while I sleep. I must have knocked it off in my sleep. When I woke and decided to check the weather I noticed I could never get a response while trying to power it up. I initially tried inserting the charger and all I could get was a black backlit screen and I noticed some static showing as well. I tried every option I could with the buttons and even connecting it to my PC. Luckily I googled what it was specifically doing and read where the battery sometimes comes unplugged inside the tablet due to some play inside its dedicated seating location. Low and behold, after I removed the back cover I found quite indeed the battery was unplugged due to the short tumble it took off my nightstand onto the carpeted floor inside its case. I was extremely lucky in my case. Just wanted to say thanks for making a troubleshooting thread like this on xda. I'm very grateful. :D
[Nexus 7 Q&A, Help & Troubleshooting] billykxda:
You're welcome.

Enjoy your N7!
[Nexus 7 Q&A, Help & Troubleshooting] johnny12times:
Hello, all.

Had a quick question and maybe follow up not so quick questions..

My (2012) nexus 7 8gb worked perfectly fine for over a year (naturally), but about 2 months ago I didn't use it for about 2 weeks. When I went to use it, it would not turn on. I plugged it in, no charging icon. Long story short, I tried the following:

leaving the device charging for at least 24 hours

unplugging and replugging the battery

leaving the battery out for 24 hours

buying a new (used) battery off of ebay

I am using the original asus charger that came with the device, but the usb cable was broken a long time ago. I never had any issues charging with another usb cable, but now I'm wondering if it's even worth hunting down and trying an original cable (I don't have any friends with the nexus 7). I'm on the verge of just selling it as is on ebay, especially after wasting another $25 on a replacement battery.

Is the original USB cable different than any other normal USB cable?

If not, any other ideas (I'm going to try leaving it charging for a week to see if it makes any difference)? I've checked all the easily accessible cables to make sure they aren't loose.

Thanks!
[Nexus 7 Q&A, Help & Troubleshooting] JovieBrett:
#2 Issue solution helped me alot. 30 sec holding the power button bring my N7 back to life :good:
[Nexus 7 Q&A, Help & Troubleshooting] billykxda:
I don't know if the OEM usb is different than any other. Charging via USB has helped some posters on this thread.

Good luck!
[Nexus 7 Q&A, Help & Troubleshooting] billykxda:
Great news!

Happy Holidays!
[Nexus 7 Q&A, Help & Troubleshooting] JovieBrett:
Merry Christmas! ?
[Nexus 7 Q&A, Help & Troubleshooting] veritasaequita:
Hello all I posted a few pages back, i had the n7 with the ubuntu install on it that went dead while booted im ubuntu and it never came back to life. here is a question that i have been meaning to askand im hoping someone has some info on. im wondering if anyone would happin to know the ballpark figures on these numbers. using a volt meter what would a full n7 battery read? or under what voltage would it bethe point of no return for the li-po battery? or maybe even what it could show as under any other circumstances. thanks to anyone who may have any info.
[Nexus 7 Q&A, Help & Troubleshooting] Super Dave426:
My daughter's 2012 N7 is just over a year old and it is dead. It gets no reaction trying everything posted so far, including the OP. The charger works, I plugged my phone into it and it charges. I pulled the battery and put a multimeter on it and it reads 4.0 volts DC, so it has juice. No button combination does anything, whether plugged into the wall or a PC or not, all combinations held for a few minutes each. It has sat plugged in for a day, battery unplugged for hours and N7 just sitting. This sucks.
[Nexus 7 Q&A, Help & Troubleshooting] billykxda:
Sorry - I don't have any good info to offer here. Maybe someone else here can.

Good luck!
[Nexus 7 Q&A, Help & Troubleshooting] billykxda:
Really sorry Dave - I don't have anything other than what's posted in the OP. Hopefully someone else can chime in here.
[Nexus 7 Q&A, Help & Troubleshooting] bftb0:
Fully charged is about 4.15v. Discharged is around 3.5v. Maybe a little bit lower than that (I rarely let mine get below 10% charge).

To get an idea about how healthy a battery is though, you really need to know how much its' output voltage droops when it is sourcing a known current. The voltage difference between open circuit and with load, divided by the current gives an estimate of the output resistance of the battery Ro = (Voc-Vl) / I

Based on some measurements I made last night, I suspect a healthy battery will have an output resistance less than 50 milli-ohms ( Ro < 0.05 ohms )

Reading around the internet, you find claims that some rechargeable batteries have a built-in safety circuit that disconnects the battery from the outside world if the voltage drops too low. For instance, if a battery were to develop an internal resistive short, it could be a fire hazard to attempt to charge it. I am not aware of whether the N7's battery has such a circuit... but if you were to measure the open-cicuit voltage of a battery and find a really low voltage (say maybe less than 3v), there is a chance that a safety circuit (if present) would not allow the battery to be charged.

hope that helps.
[Nexus 7 Q&A, Help & Troubleshooting] Super Dave426:
Reading your post I removed the back and unplugged the battery and put a new battery into my multimeter and I only got 3.4V on the battery. What I did next is get out my automotive battery charger, set it to 6 volts and used 2 1/2" finish nails to make contact. I held it to the contacts for 5 minutes, switching every 30 seconds, checked and the voltage went up to 3.73, so I felt the battery and examined the wires, they weren't heating up so I held the charger in place for 6 minutes, switching contacts every 60 seconds. I then plugged in the battery and hit the power button,,,,,,,BOOM, it booted! It read 28% on the battery, I then plugged it in with 3 different chargers and cables and nothing gets a reaction.

So I took the back off and unplugged the battery and manually charged for 10 minutes, switching every 60 seconds. Then I unscrewed the USB port but couldn't find any damage, so I put it all back together and turned it on, it's at 42%, but nothing happens when plug it in so I guess I need to order a new USB port and see if that helps. I know I can't hold the charger every time and if I can find a docking station that will charge off the side maybe I'll get one to be on the safe side.

Thanks again for your information regarding how many volts a dead battery has, I felt that it had enough since it wasn't zero.

Edited to add, looking around the Dock charges through the USB Port so that wouldn't help, I haven't seen anything to charge off of the side contacts, the POGO Port.
[Nexus 7 Q&A, Help & Troubleshooting] bftb0:
[size=+3]Holy Crap BE CAREFUL![/size]

Hopefully your "Auto Charger" has some way to limit current to something less than 2 A. It could be quite dangerous to dump too much current in to your battery - or produce long-term damage to the battery.

Batteries usually have a very low output resistance - if you don't have a way to limit the current you could cause a fire (or worse yet - an exploding battery).

In particular, the OEM charger only charges the battery at about 0.7% per minute - for you to see a 28% charge in only a few minutes of charging sort of implies you were dumping a huge amount of current into that battery!

PLEASE BE CAREFUL! - I didn't recommend any such behavior.
[Nexus 7 Q&A, Help & Troubleshooting] Super Dave426:
The charger is rated at 4 Amps, I knew it was more than the battery was used to so I watched it closely, and kept switching up the contact to the charger. It was the only charger I have that has the polarity clearly marked, and I wanted to know if it is the battery causing the problem or other, so for me it was worth it. Sadly a new USB Port is $60, sure there are a few around $40 that ship from Hong Kong and could be here in 3 or 4 weeks, so I chose the one that will be here by Tuesday. Without the Port there isn't any way to remove any of data for backing up so it is needed for more than just charging.
[Nexus 7 Q&A, Help & Troubleshooting] Super Dave426:
New USB came today, took 10 minutes to install and all is fine again, works great.
[Nexus 7 Q&A, Help & Troubleshooting] bftb0:
Nice result. Thanks for explaining what you did. I took some more refined measurements of charging and discharging of my (grouper) N7, I will try to summarize that info soon.
[Nexus 7 Q&A, Help & Troubleshooting] Hextall:
I think I might have a different issue than the focus of this thread, but it's similar enough I thought I'd ask here.

I cannot charge my 2012 N7 purchased and happily used since august '12. It is unrooted and stock. I'm using the OEM charger and cable. I tried all the tricks of the OP, and can't get it to charge over the past day or so (it was turned off and charging overnight).

When plugged in, I get the charging icon, both turned on or completely turned off. I tried swapping cables, still no charge.

Any ideas? Here's a screen shot of my battery history over the past two days (it was off last night plugged in and all of today unplugged, so it's really teh past 2 days).
[Nexus 7 Q&A, Help & Troubleshooting] thinhduckhoi:
Hi guys, i have the issue #1. A little bit detail: Every time my nexus 7 turned off by itself, then i turn it on and the battery was drained about 30%. For example today, it turned off twice and the battery was drained from 88% to 55% and from 55% to 31%. I popped the back cover to figure out if the battery connection is loose but that's not the problem. My nexus 7 keeps turning off itself. What should i do now? (, now i'm using 4.4.2 stock, i tried factory reset but it didn't work.)
[Nexus 7 Q&A, Help & Troubleshooting] billykxda:
Sorry, but I don't have any ideas for this issue.

Maybe someone else here can contribute.

Also, consider making a separate thread just for this issue.

Good luck!
[Nexus 7 Q&A, Help & Troubleshooting] billykxda:
Not sure why you couldn't do a factory reset. Are you sure that you are doing it properly? How did you attempt to do this?

Also, did you try every suggestion in the OP?
[Nexus 7 Q&A, Help & Troubleshooting] thinhduckhoi:
I did factory reset a few times but after that, my nexus still turn off itself. Speaking of loose battery connector, i didn't reseat battery but i saw its not loose so i didn't do anything. How did you add a piece of tape? I mean where? Can you show it?

Ah, btw it just turn off itself when i left it idle, maybe for a few hours but sometime just fews minutes. That's weird.
[Nexus 7 Q&A, Help & Troubleshooting] threevolve:
That's not how electricity works... amperage is drawn by the load not pushed to the load. You can safely plug a 1A device into a 2A charger, it will happily draw 1A from it. The danger with lithium ion batteries comes from them being overcharged, having too much charging *voltage* applied, and overheating.

That said, attempting to manually charge a lithium ion battery directly is an incredibly stupid idea. This is how explosions happen.