Your Nexus 7 is still under warranty, why not go down that route before messing around replacing batteries and thereby invalidating your warranty?
What kind of special warranty are you talking about jpash? The Nexus 4 was first released in July last year, barely 8 months ago. In any country on the planet the Nexus is within warranty. The OP said in one reply he was going to ship it under warranty so I don't know why people are advocating actions that would invalidate that warranty potentially leaving the OP seriously out of pocket.
First port of call whenever something you have bought is defective and it is within the warranty period is either the place you bought it from or the manufacturer. All you need to tell Google/Asus is your device no longer charges. Don't tell them you left it sitting for 5 months!
Sorry again about my bad advice but I certainly would not advise dishonest or misleading discussions with Asus. There are special warranties available from Square Trade,Walmart, Staples etc in US. Don't know where OP is located. Of course the standard Asus warranty applicable in the US is a limited warranty. This usually covers defects in materials and workmanship happening under normal usage but not damage caused by misuse or operating errors. Since you were going to send it back to Asus perhaps you discussed the warranty aspects with them and have some idea as to what is going to happen. Don't know if you discussed the issue of neglecting to charge or anything else with them. If returning for repair is what you decided don't take the back off or do anything. Don't believe you said what version of Jelly Bean the unit was on but suppose it was 4. 1. My advice as to battery replacement was to taken as an alternative to pitching in a drawer or getting into a losing fight with Asus.
"Another trick which has been reported in other threads in Android Central is :
bugs that we are slowly figuring out fixes for. One of those that has plagued many (according to a variety of forum posts), is a charging issue with the Nexus 7. As users leave their tablet idle for an extended period of time or use it for hours until the battery runs completely dry, the device is having a hell of a time charging back up again or even turning on.
In fact, if you let your Nexus 7 die completely, you may run into a screen flashing or pixel party experience once plugged into a charger that won?t bring you joy. The device, at least mine and in others? cases, won?t turn on with any combination of button pressing. Well, there is one combo along with a charger that worked for me, getting my N7 back on the charging path of pleasure.
To charge a dead Nexus 7:
1. Plug-in your dead N7 to a wall charger. (Jump immediately to step 2.)
2. Immediately after plugging it in, press Volume Down and Power at the same time.
*This should get you into the bootloader menu. You may have to try this with different chargers or test out the timing in order to get it to work.
3. Once in the bootloader menu, use Volume Down until you see ?Power Off Device.?
4. Choose that option with the Power button.
5. Once your device is off, unplug the charger and then plug it back into the device.
6. You should now see the battery meter (pictured above) with your device returning to life.
Hope that helps those of you with dead Nexus 7s. For the rest of you, I suggest not letting your N7 completely run out of juice. Should you see it drop to 10% or under, find yourself a charger.
Via: Android Central"
An URL reference to the same thing follows:
http://www.pchelpforum.com/xf/threads/nexus-7-will-not-charge-asus-warranty.143281/
From my N7 or BBPB or HPTP or HP Laptop