You can also go to Settings > Power and toggle on Automatic Smart Suspend.
Or you could factory reset the device and install apps selectively, watching out for any changes in battery drain. You could go to Settings > Apps & Games > Manage All Applications and try uninstalling apps one by one and testing to see if you can find the culprit.
There are a number of discussions on these topics within the Amazon forum. Some Fire tablet owners have run into issues with sudden and unexplained battery drain. Let your router and modem boot back up then try connecting from the tablet.
Give this a try if your tablet is acting up, not responsive, or running slowly. To do that, simply p ress and hold the power button for 40 seconds or until your device restarts. If you find that your tablet is not responsive or frozen, then performing a soft reset is probably your best bet. If you’re still having issues then you may have to send your tablet in for service or take it to your trusty local third-party repair shop to repair a fault charge port or battery. Your Fire tablet indicator light turns orange while charging.
After making sure that your tablet is not in an environment that’s too hot or too cold, try the following steps to resolve your charging issues.