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I have had my S3 for a good long while, ever since they were new with Verizon. Almost immediately, I bought an extended battery and all was good. In the last week or so, the battery has begun discharging rapidly. 50% in a couple of hours. I had extra batteries, so I switched out thinking I had a bad one. Same deal.

Looking around, I read that killing the cache should fix it. Nope. Then someone suggested turning off auto-sync. That did it. Battery drain want back to normal. Why? Why all of a sudden? Then, the Gmail app doesn’t want to manually sync… Annoying. I was hoping to avoid a factory reset, but would that be my next course of action? I’m wondering if the Gmail app is bad. Definitely going to dump that and re-install.

Any thoughts?

  • Is it just the gmail app? Or are other auto-sync apps also guilty of battery murder? – Colin Jun 18 '14 at 2:33
  • Settings → More → Battery will show you which app(s) use the most battery. Check there, and then update your question with what you found out. – Dan Hulme Jun 18 '14 at 5:36
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I hava a Samsung S5. Before I charged my phone once per 24 or 48 hours and since a few days suddently the battery lasted only 4 to 8 hours. After several test I discovered the cause was a few corrupt images. I deleted the corrupt images and the problem was solved. I used this app to find the corrupt images.

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It is not "Constantly" trying to update, and therefore it is not constantly using your battery.

Autosync only transmits when the other side has something to send. It doesn't constantly ask if there has been a change that needs to be synced.

This is accomplished by opening a socket to the server, then putting the radio to sleep. The socket stays open until server attempts to send something, or the socket times out. TCP/IP sockets typically time out anywhere from 12 to 18 minutes after they are opened.

Each time the radio listens for traffic (which in GSM land is every 120 milliseconds) it will see that traffic is waiting if EITHER the socket timed out or the socket became readable (has data waiting). It would then power up the radio enough to read the data, or reestablish the timed out socket).

Your phone is doing that all the time, 24/7 365 whether you have autosync on or not. That's how cell phones work. It takes virtually zero power.

So if you sync your Gmail, Contacts, Calendars, Picasa, Documents, Books, Music, Reader, all of those things you sync with Google are handled by ONE socket. That one socket gets set readable when there has been any change in any of those services that needs syncing.

Add another socket for Dropbox, or skydrive, or any non-Google mail accounts.

(For non-google mail accounts ALWAYS choose IMAP accounts, never POP3. Pop3 has to wake up and check mail. Have your gmail account pull mail from pop3, and get that account off your phone. IMAP accounts use IMAP IDLED, which works on the open socket method described above, as does Microsoft Exchange).

The vast majority of these services go hours if not days between any changes, so there are very few times that data needs to actually be synced. Most of the time its just a socket refresh. And all of these tend to happen at one time, because Android tries to get them to all drop at the same time by starting them at the same time when you bounce from one tower to the next or switch from cellular to wifi.

But the key point to remember is that your phone is ALWAYS talking to the towers anyway, every 120ms, so these socket refreshes take almost zero extra power.

Source: icebike's answer on http://forums.androidcentral.com/htc-one-x/181151-autosync-battery-killer.html

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  • Wow! That is a great answer. Thank you, you really helped me with understanding this functionality. But this being said, why do you think the dramatic battery drain slows (dramatically) with auto-sync turned off? – user64252 Jun 18 '14 at 13:32

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