Update: although the post was initially written for Galaxy Note with ICS, the method actually works for Galaxy Note 2, Galaxy Note 3 and many other Android devices with different versions of Android.
After ICS update, some Galaxy Note users complained about poorer battery life compared with that with Gingerbread. Initially, I thought it is a problem of “feeling” because I personally felt similar battery life after the ICS update. I was a bit disappointed because I had expected some sort of battery life improvements.
Suddenly, last week, I encountered the battery drain issue: battery just draining crazily. In one hour it can drain 3-10% battery capacity when the phone is idle. So, I know the users complaining are not alone.
As I finished my investigation and found the culprit, now I share with you how to solve battery issues on your Galaxy Note after the ICS Update. If you already have battery issues or you feel you have battery issues, you may follow my steps.
First, I installed an free app called CPU Spy (https://play.google.com/store/apps/details?id=com.bvalosek.cpuspy), which will give you the duration of each CPU state. When your phone is idle (screen off, no music playing, no downloading), normally, your CPU should be in “Deep Sleep” state. For example, after one night, you check your CPU Spy, it should look like this.
As you can see, this is the normal situation. In the night, 95%of the time, the CPU is in deep sleep, and after 11 hours, about 6% battery was drained (I also checked emails before sleep). If your phone does not go to deep sleep, you will find the duration on other state is higher. Very likely, you have battery drain issues if more than 20% battery are drained when you are sleeping (6-10 hours), You probably will find far larger percentage on 200MHz state. If more than 30% are drained in one night, very likely, your phone never goes to Deep Sleep state.
So, install the CPU Spy (free), use your Galaxy note as usual for a few hours, fully charge your phone, disconnect your Note from the charger, close all apps (it is NOT necessary to clear the cache; but is a good idea to disable WiFi). Then go to sleep. Check the battery status after 6-10 hours (if you can sleep that long).
If the battery drain is less than 1% per hour (this gives discharging rate of less than 25mA, as your Note has a 2500mAh capacity) in idle state, you phone should be able to go to deep sleep state and don’t worry for the battery drain issue for the time being (as you may encounter another issue as I did).
If your phone drains battery faster than 1% per hour when you are sleeping. It means the phone has an insomnia problem. You need find out which app casues the problem.
Now you need installed another app named Better Battery Status (https://play.google.com/store/apps/details?id=com.asksven.betterbatterystats&hl=en). If you want to support the author for this incredible app, you can buy it for about $2. Yes, if you are just want to do a short time test, you can download the identical (and also official) free one from XDA-Developers (http://forum.xda-developers.com/showthread.php?t=1179809). This is an official copy the author released for XDA-Developer community for free. You can find the download link for the APK file in the second post. Once the APK file is saved on your Note, you can then use any file exploer (e.g., MyFiles) to browse it and you will be offered to install it. Please make sure the Unknown sources is checked (under Settings–Security–Device Administration) if you install from APK file instead of the paid one from the Play store.
Once you start Better Battery Status, you can straightaway see a lot of info. You can select Partial Wakelocks since unplugged if you want to find out which app prevents your phone from going into deep sleep. Here is an example (normal situation, no issues).
So, in the past 19 hours, some apps just keep the phone awake for a few mins. If you find any apps that listed here has long time associated with it (do NOT judge on the length of the bar; you should make judgement based on the percentage of this time to the total time), congratulations, you find the culprit. You can proceed to check the app settings.
Again, the image above indicates there are no problems. The longest partial wakelock is only a few mins. Don’t be panic when you look at the bar.
As I told you at the start of this post, last week I encountered battery drain issues caused by the kernel, possibly a kernel bug. All of a sudden, my Note went crazy: draining the battery very fast. Initially I though it could be caused some apps. But after I checked the battery status, I found out it was caused by the kernel (fuel_alerted). and here is the screenshot.
Anyway, this is a kernel bug in ICS, we have to wait for new update. The solution for this is: shutdown your Note, peel off the back cover, remove the battery; hold the battery for more than one min, put the battery back, put back the back cover; start the phone. Then, everything goes back to normal. Reboot your phone will NOT solver this issue, at least for me.
Next time, when you encounter this issue again, try the procedure again.
But it seems it is hard to hit the bug again. I tried to enable/disable power saving; tried to reboot, tried to turn on/off GPS, I simply cannot get the problem again. I know the problem is NOT fixed, it will come out someday, but I don’t know when. We have to wait for another update to permanently fix this issue.
Do you have any other battery issues? Does this guide work for you?
More tips on Galaxy Note, Galaxy Note 2, Galaxy Note 3, Galaxy Note 8.0 and Galaxy Note 10.1 can be found in Tips and Tricks page.
Tutorials for S Note app can be found here in the S Note guide page.
Galaxy Note 3 online manual (HTML edition) is available here.
If you want to download the PDF version of Galaxy Note 3, Note Ii, Note 8.0. Note 10.1, or read the PDF version on line, you can find all of them in this User Manual page.