Battery drain with sleeping Galaxy Tab 2 7"

[HarryT]

I've noticed that when my Galaxy Tab 2 7" is asleep, the battery will drain about 10% overnight. This is with WiFi, Bluetooth, GPS, etc, all disabled. So even if I don't use the tablet at all, a fully charged battery will drain flat in about 5 days. My iPad, on the other hand, seems to use essentially no battery while asleep.

Is what I'm seeing normal for Android? Is there anything I can do to reduce the battery drain (other than turn it off when not in use)?

[Jabby]

Originally Posted by HarryT

I've noticed that when my Galaxy Tab 2 7" is asleep, the battery will drain about 10% overnight. This is with WiFi, Bluetooth, GPS, etc, all disabled. So even if I don't use the tablet at all, a fully charged battery will drain flat in about 5 days. My iPad, on the other hand, seems to use essentially no battery while asleep.

Is what I'm seeing normal for Android? Is there anything I can do to reduce the battery drain (other than turn it off when not in use)?

Have you tried airplane mode? I automatically turn it on with a new tablet since past experience has shown me that Android keeps trying to turn on a phone radio even if none is present.

Regards - John

[HarryT]

I'll try that, but surely turning WiFi off does the same thing, doesn't it?

[Jabby]

Originally Posted by HarryT

I'll try that, but surely turning WiFi off does the same thing, doesn't it?

There is an app called "phone.apk" that you can find if you are rooted. If I root my tablet I rename the app which will keep it from running. I don;t know if ICS has fixed this problem but earlier version of Android ran the app even though there was no phone radio present.

What was happening was that the app tried to turn on the phone in a continuous loop even when asleep. Android was designed as a phone OS and phones are not supposed to go to sleep. It's the app that is depleting your battery if this condition still exists.

Wi-fi works in "airplane mode" so you'll still need to turn it off when you put the tablet to sleep.

Regards - John

[HarryT]

I've turned on "flight mode"; we'll see if that makes any difference.

Thanks for the suggestion.

[paulsalter]

Seems a bit high, I see about 3% drain over night

have you looked under settings and then battery, see if any apps are showing as more battery use than normal, if you go into the apps from here see if any are showing as 'keep device awake', this run the battery down quicker, if you need the app though there is not much can be done about it

or turn it off then back on before you go to bed, check in the morning what has been using battery, as it should be no usage from yourself

[HarryT]

Originally Posted by paulsalter

Seems a bit high, I see about 3% drain over night

have you looked under settings and then battery, see if any apps are showing as more battery use than normal, if you go into the apps from here see if any are showing as 'keep device awake', this run the battery down quicker, if you need the app though there is not much can be done about it

or turn it off then back on before you go to bed, check in the morning what has been using battery, as it should be no usage from yourself

I've never been sure about the battery app. Are the % figures shown against apps what's using power NOW, or what's used it over the current battery charge lifetime?

[paulsalter]

its out of what has been used

eg, if it says screen/display has used 50% of the battery and your battery is at 70%, it has used 50% of 30% (battery used), so it has used 15% of the battery

if that makes sense

[HarryT]

Originally Posted by paulsalter

its out of what has been used

eg, if it says screen/display has used 50% of the battery and your battery is at 70%, it has used 50% of 30% (battery used), so it has used 15% of the battery

if that makes sense

Thanks, yes - that's what I was asking: so it's the cumulative total of power usage by each app, not an instantaneous snapshot of what's using the power at the instant you run the app. Thanks for clarifying that for me!

I've just fully charged my Tab, so I'll leave it till the morning and see what shows up then.

Appreciate the help - thanks.

[paulsalter]

correct, its a cumulative total since the last full recharge or device restart (not 100% on device restart as dont do it often but think so)

[HarryT]

Got it - thanks . Stay tuned for the results, tomorrow!

[SeaKing]

I had vehicle with all sorts of electronics, and if you parked it at the airport, it would have used a lot of battery when you got back say a week or two later. You might have to jump it with another vehicle or a jump box and once I just carried an extra battery.
I couldn't find out easily what was going on, so finally I started just taking the cable off the battery terminal and keeping a little wrench to do it with in the cab.
Then winter came and I left the vehicle at a northern airport in the winter and ice and snow built up on the hood and I had a hard time getting the hood up so I could re-attach the battery cable.
Having a little tech in my blood, I thought well I can put a relay in the line to the battery terminal and power that on and off from the cab with a toggle but then I would need a power source, and dah, dah, dah. Whoa!
Finally I got a simple disconnect with a handle, mounted it on a board and mounted that in the engine compartment, put it inline electrically with the battery terminal, connected a nylon cord loop to the handle so that if I pulled on one leg, it would disconnect, pull on the other it would connect. (Arranging that cord was the only hard part.) I put a very small hole with a gasket in the engine bulkhead to the cab to run the cord through and I was done. Had that for 3-4 years. I had thought I might lose the time on the clock, but it must have had a battery backup and when it came back on, it was always correct. When I sold the vehicle, I pulled everything out leaving no marks, plugged the gasket in the bulkhead with silicone and sold "a really great truck."

On an android phone, you can just pull the battery out until you want to use it, but I guess the tablets don't have removable batteries.

[HarryT]

OK, here are the results:

97% - Discharging
13h 5m on battery

51%: Device idle
43%: Screen
6%: Android OS

That's a LOT better - only 3% discharge! It seems that the tip to select "Flight Mode" really has made all the difference.

It's interesting, though, that "screen" has used 43% of the power even when the device has been asleep. I wouldn't have expected it to use any power.

[paulsalter]

that screen figure is probably just when you looked at the device to check the figures

if you click into it you will see an HHMM of how long its been active (depending on how much you have used it this morning you might be able to work it out)

[HarryT]

Yes, you're right. Battery is now at 96% (after 18h 39m) and I've got:

48%: Device idle (18h 35m)
46%: Screen (4m)
6%: Android OS (CPU total 42s, Stay awake 12m)

This is starting to make a lot more sense now. Very many thanks