Related
Hey guys. I was just wondering if there was any step above "Good" in Quick System Info (app) regarding battery health. My battery did have some problems with Darchstar's 2.1 AOSP, such as losing 13% battery instantly, so I just want to make sure there is no "Excellent" above the "Good Value".
mine shows good also so i guess that is normal.
i had had my phone since it came out
There's no reading above good,that's normal
Thanks guys!
Mine says "Awesomely smokin'!" Is this a glitch?
dennistpm said:
Mine says "Awesomely smokin'!" Is this a glitch?
Click to expand...
Click to collapse
Your batteries too hot
dennistpm said:
Mine says "Awesomely smokin'!" Is this a glitch?
Click to expand...
Click to collapse
lol...........
Anyone have one that says bad?
hello to all friends i bought a nook color but i have problem with charging it takes more the six hour for full charge i am using nook color charger with micro usb and laptop for charging it is normal or some thing is wrong with my nook color thanx from all XDA froum
I am using the cm7 custom rom
afghan-gsm-mastermind said:
hello to all friends i bought a nook color but i have problem with charging it takes more the six hour for full charge i am using nook color charger with micro usb and laptop for charging it is normal or some thing is wrong with my nook color thanx from all XDA froum
I am using the cm7 custom rom
Click to expand...
Click to collapse
Your problem might be using the laptop as a power source. If you use the wall charger it should completely charge from 0 to 100 in about 4hrs
Sent from my NookColor using Tapatalk
thanx for ur replay
Can u tell ur nook color how long keeps the charge when i am watching the vedio every 3 minuts one parcent came down i mean if i watch vedio when all other comunication is off like wifi bluthuth and other comunication so if i continue watching vedio it will keep its charge 300 mints so what u friends think ? I think my battry have problem becuse i bought the nook color from my friend.
If my battry have problem i think i cant find it in afghanistan thanx friends
1. use the wall charger, it charges real fast. charging from a laptop with the included cable is not a good idea.
2. There are a lot of things you can do to improve battery life, most of which will require rooting and flashing a different ROM besides stock, just so you can get to the settings that make a difference. 5 hours of battery life on a stock NC playing videos is probably about right. I get 10+ hours of video out of mine with extensive tinkering. Far and away the biggest factor is the screen brightness, and beyond that, how bright, on average, is the video. I watch movies with brightness about 9-11%.
thanx mr 72 for replay
i am using cm7 custom rom
So what should i do to do beetter for battry life i am watching vedio in 0% brightness plz help i want to see vedio a bout 10 hours if poossibl thanx
Battery life will be affected by any radios, screen brightness, and CPU clock speed. The nook is not meant be charged over USB, but as you can see, it is possible. If you're looking to get a ten hours battery life, and you've purchased and rooted the wrong tablet. Id say nook color can get anywhere from 5-7 hours based on the above factors.
Mine takes 4 hours but my nook needs to be off to charge. If it is left on even with the screen off and saying charging, the battery is actually going down. Kinda stupid but whatever this thing is cheap greatness lol
Sent from my NookColor using Tapatalk
vulcan4d said:
Mine takes 4 hours but my nook needs to be off to charge. If it is left on even with the screen off and saying charging, the battery is actually going down. Kinda stupid but whatever this thing is cheap greatness lol
Sent from my NookColor using Tapatalk
Click to expand...
Click to collapse
Really? I that's interesting. I can charge mine in about seven hours with the screen on and in use.
AnnonymousFalcon said:
Battery life will be affected by any radios, screen brightness, and CPU clock speed. The nook is not meant be charged over USB, but as you can see, it is possible. If you're looking to get a ten hours battery life, and you've purchased and rooted the wrong tablet. Id say nook color can get anywhere from 5-7 hours based on the above factors.
Click to expand...
Click to collapse
NC can certainly get 10+ hours of battery life under normal use, and up to 17+ hours in my experience if you are using apps that require no wifi, low CPU and can tolerate low brightness settings.
Follow the guide in my sig.
mr72 said:
NC can certainly get 10+ hours of battery life under normal use, and up to 17+ hours in my experience if you are using apps that require no wifi, low CPU and can tolerate low brightness settings.
Follow the guide in my sig.
Click to expand...
Click to collapse
I suppose under the correct settings you could. Is this including sleep time or solely screen on?
AnnonymousFalcon said:
I suppose under the correct settings you could. Is this including sleep time or solely screen on?
Click to expand...
Click to collapse
That's "on" time.
17+ hours of actively reading ebooks (Moon+ reader in my case, black text on off-white background, no wifi enabled [was on a plane], brightness around 10-15%)
10+ hours of actively watching movies (MX Video Player, movie format varies from 720P to 480P DVDrip h264 and xvids, also no wifi, on a plane)
I say "+" because I quit using the NC and there was remaining battery, so I don't know how long it would have run if I let it run to zero. Check out my guide (in my sig) to see how I set mine up. There are no settings that compromise performance or utility.
I find charge time can vary pretty greatly. Last night i didn't get a full charge with the same settings that I had the night before.. aside from updating to a new nightly. Generally I can charge the device in less than 5 hours if the wifi is off and nothing is running.
I'm going to piggyback this forum as I have been searching over 40 min and this looks closest. Sorry ahead of time.
I also found it takes forever to chafe my nook. I have a droid raze and ourchase local for it so I'm using in my nook to shutbdown the wifi from 1am to 6.am. hmm I may change that to. 12:69 am. It will help with my issue but I still have the the following request.
Wifi seems to be eating up battery life. Does anyone know of a program that will auto off wifi if not used for say at min?
Also for other readers: I found a simple free program called connections (for the bionic connectivity issues) I use it on the nook when there seems to be an issue. I have a shortcut in app launcher so its avail in any program.
Any feedback welcome.
Sent from my NookColor using Xparent Cyan Tapatalk
Droidatar said:
Wifi seems to be eating up battery life. Does anyone know of a program that will auto off wifi if not used for say at min?
Click to expand...
Click to collapse
No, but if you leave the defaults, then wifi should be off while sleeping.
Or you can use the status bar pull-down in CM7 to turn it off when you are not using it.
However, I find that it doesn't make a huge difference.
Droidatar said:
[...] Wifi seems to be eating up battery life. Does anyone know of a program that will auto off wifi if not used for say at min?
Click to expand...
Click to collapse
I am using Juice Defender Ultimate on my NC running rooted B&N 1.4.1 for exactly this purpose, and it is working well. I also tried Green Power, but had problems with it.
JD is definitely overkill, since it's meant for device with more radios. You could also use Tasker and set it up to turn off wifi when the screen goes off.
bobstro said:
I am using Juice Defender Ultimate on my NC running rooted B&N 1.4.1 for exactly this purpose, and it is working well. I also tried Green Power, but had problems with it.
JD is definitely overkill, since it's meant for device with more radios. You could also use Tasker and set it up to turn off wifi when the screen goes off.
Click to expand...
Click to collapse
I looked at tasked but thought it would be overkill since I already have local set to turn off at 1am.
I will check out jd as I may use on my raze as well.
Thanks.
Sent from my NookColor using Xparent Cyan Tapatalk
mr72 said:
No, but if you leave the defaults, then wifi should be off while sleeping.
Or you can use the status bar pull-down in CM7 to turn it off when you are not using it.
Click to expand...
Click to collapse
Thanks, I did not realize the default for cm7 was off during sleep. I will test but I can swear upon wake it would be found I forgot and left the wifi on. I will check that setting.
Thanks again for your response.
Sent from my NookColor using Xparent Cyan Tapatalk
Hello everyone, i purchased my Nexus 7 and it arrived in the mail 3 days ago. And as with every other Android device ive ever owned, the batter is absolutely terrible. I get about 2hrs on screen time when browing the web and maybe playing an occasional game. Does anyone have any idea whats going on? Or have any way to help? Thanks so much
That is pretty bad. Try a factory reset. Might be something you installed.
I'd hate to do a factory reset cause I just barely got it set up but..I'll try it anyway tonight
Sent from my SGH-T999 using xda premium
Scoutamis said:
I'd hate to do a factory reset cause I just barely got it set up but..I'll try it anyway tonight
Sent from my SGH-T999 using xda premium
Click to expand...
Click to collapse
Doing a factory reset before installing anything is becoming the gold standard.
Hope it helps you.
I get between 7-9 hours of active use. Sounds like some process is running amok on yours. I didn't factory reset when I bought it either....though I have rooted it since then, but battery life is about the same pre and post root.
You might want to consider a program to monitor battery use to see what's eating it up. Maybe do that before you factory reset it so you don't install the same thing again.
ScandaLeX said:
Doing a factory reset before installing anything is becoming the gold standard.
Hope it helps you.
Click to expand...
Click to collapse
Really? Like as soon as you set up the device, you are suppose to factory reset it? And since im facotry resetting it 3 days into having it, do i have to calibrate the battery again?
ExploreMN said:
I get between 7-9 hours of active use. Sounds like some process is running amok on yours. I didn't factory reset when I bought it either....though I have rooted it since then, but battery life is about the same pre and post root.
You might want to consider a program to monitor battery use to see what's eating it up. Maybe do that before you factory reset it so you don't install the same thing again.
Click to expand...
Click to collapse
Do you have any battery monitoring apps in mind? I would love to see what is eating up my battery
Scoutamis said:
Do you have any battery monitoring apps in mind? I would love to see what is eating up my battery
Click to expand...
Click to collapse
System panel is a good app to find what's using your CPU and better batterystats can help find what's keeping your phone from going to deep sleep. An easy way to see if this is the case is go into battery setting and select the first option(history details). Compare the Awake bar with the screen on bar. Those two should be nearly identical if not then you have a rogue app.
Scoutamis said:
Do you have any battery monitoring apps in mind? I would love to see what is eating up my battery
Click to expand...
Click to collapse
The one I've seen mentioned several times in here is BetterBatteryStats. I just don't want to drop $3.00 on something I don't need. It might help your issue though.
https://play.google.com/store/apps/details?id=com.asksven.betterbatterystats
neotekz said:
System panel is a good app to find what's using your CPU and better batterystats can help find what's keeping your phone from going to deep sleep. An easy way to see if this is the case is go into battery setting and select the first option(history details). Compare the Awake bar with the screen on bar. Those two should be nearly identical if not then you have a rogue app.
Click to expand...
Click to collapse
Alright ill try system panel, and i looked at the battery setting and awake and screen on are almost exactly the same.
ExploreMN said:
The one I've seen mentioned several times in here is BetterBatteryStats. I just don't want to drop $3.00 on something I don't need. It might help your issue though.
https://play.google.com/store/apps/details?id=com.asksven.betterbatterystats
Click to expand...
Click to collapse
Well then, here you go:
http://forum.xda-developers.com/showthread.php?t=1179809
Scoutamis said:
Alright ill try system panel, and i looked at the battery setting and awake and screen on are almost exactly the same.
Click to expand...
Click to collapse
have you flashed any kernels or roms? sometimes this makes the tablet report the wrong battery stats for a bit.
did you run the battery down until it turns off and then give it a full charge? sometimes you have more juice than what is being reported. ive been stuck at 1-2% for over an hour before. Most likely its a rogue app though, system panel and better batterystats should find out what app it is. if they dont then it could be that you have a defective battery...
Been on mine continuously for 3 hrs 18 mins and at 60%. Excellent if you ask me. Next step up in battery life would be Transformer series with dock.
Scoutamis said:
Hello everyone, i purchased my Nexus 7 and it arrived in the mail 3 days ago. And as with every other Android device ive ever owned, the batter is absolutely terrible. I get about 2hrs on screen time when browing the web and maybe playing an occasional game. Does anyone have any idea whats going on? Or have any way to help? Thanks so much
Click to expand...
Click to collapse
Quite the opposite for me; unlike every other Android device I've had (Nexus One, GS2) the battery life is excellent. I watched 720p mkv video on the train yesterday for a good 3 hours, and still had ~70% by the time I got home, from a full charge.
The battery life is excellent, as far as I'm concerned.
Scoutamis said:
Really? Like as soon as you set up the device, you are suppose to factory reset it? And since im facotry resetting it 3 days into having it, do i have to calibrate the battery again?
Click to expand...
Click to collapse
Don't think you needed to calibrate the battery to begin with. I usually get fine battery life without doing anything special.
Something must be causing the poor battery on your Nexus, Yesterday after my N7 was fully charged, I watched the movie Thor for 1hr and 54 minutes n and my battery only dropped to 83%.
I'm at 16 hours and 52 minutes with 3 hours and 44 minutes of on screen time, the battery is at 51%
Sent from my Nexus 7 using Tapatalk 2
neotekz said:
have you flashed any kernels or roms? sometimes this makes the tablet report the wrong battery stats for a bit.
did you run the battery down until it turns off and then give it a full charge? sometimes you have more juice than what is being reported. ive been stuck at 1-2% for over an hour before. Most likely its a rogue app though, system panel and better batterystats should find out what app it is. if they dont then it could be that you have a defective battery...
Click to expand...
Click to collapse
My N7 is completely stock and has never been rooted. I also did do a couple charge cycles which didn't seem to help much. And better batterystats has AudioOut_2 at 38% (while I'm playing music) but other than that it doesn't seem to be a rogue app
Sent from my Nexus 7 using XDA Premium HD app
Download CPU spy from the market to see if the tablet is sleeping properly, and what frequency its constantly running at
Scoutamis said:
My N7 is completely stock and has never been rooted. I also did do a couple charge cycles which didn't seem to help much. And better batterystats has AudioOut_2 at 38% (while I'm playing music) but other than that it doesn't seem to be a rogue app
Sent from my Nexus 7 using XDA Premium HD app
Click to expand...
Click to collapse
Unless you listen to music for over 5 hours or streaming the songs it shouldnt use that much battery. If you can't find a wakelock with better battery stats then it might just be a bad unit.
Hello, I have a Nexus 7 16Gb. I have been using it for about 20 days. Battery life was amazing. All of a sudden yesterday I noticed that i had a huge battery drain when using it. Installing Battery Calibration from the play store I saw that my maxumum charge was only 4 mV while it should be around 4200 mV. Is there a way to fix it or my battery is faulty. Have in mind that I have rooted it, and I have Codename Android rom, along with motley kernel v 1.1.1. I dont know if its a coincidence but just before I notice that drain I followed that guide. http://forum.xda-developers.com/showthread.php?p=30864511#post30864511
Any ideas on how I should proceed?
sotoskawasaki said:
Hello, I have a Nexus 7 16Gb. I have been using it for about 20 days. Battery life was amazing. All of a sudden yesterday I noticed that i had a huge battery drain when using it. Installing Battery Calibration from the play store I saw that my maxumum charge was only 4 mV while it should be around 4200 mV. Is there a way to fix it or my battery is faulty. Have in mind that I have rooted it, and I have Codename Android rom, along with motley kernel v 1.1.1. I dont know if its a coincidence but just before I notice that drain I followed that guide. http://forum.xda-developers.com/showthread.php?p=30864511#post30864511
Any ideas on how I should proceed?
Click to expand...
Click to collapse
There's no way it would run on 4 mV.
What app does it say is eating the battery in Settings -> Battery[/b[?
mvmacd said:
There's no way it would run on 4 mV.
What app does it say is eating the battery in Settings -> Battery[/b[?
Click to expand...
Click to collapse
Thank you for your replay. Well i thought of that but the screens dont lie... I am hoping that its a bug. Anyway the drain is real though...
sotoskawasaki said:
Thank you for your replay. Well i thought of that but the screens dont lie... I am hoping that its a bug. Anyway the drain is real though...
Click to expand...
Click to collapse
wow..well, apps do mess up sometimes.
and I dunno about everyone else, but to me the "Screen" looks like it's using a ton of battery. do you just leave the screen on all day doing nothing? the next runner up is only at 3%...seems a bit odd to me. Is the brightness all the way up or something?
Anyway if you reflash the stock rom and/or try a different ROM and you still have this problem, I think you will be able to RMA it.
did you get it thru Google Play?
Also, approx how long does the battery last on a full charge?
mvmacd said:
wow..well, apps do mess up sometimes.
and I dunno about everyone else, but to me the "Screen" looks like it's using a ton of battery. do you just leave the screen on all day doing nothing? the next runner up is only at 3%...seems a bit odd to me. Is the brightness all the way up or something?
Anyway if you reflash the stock rom and/or try a different ROM and you still have this problem, I think you will be able to RMA it.
did you get it thru Google Play?
Also, approx how long does the battery last on a full charge?
Click to expand...
Click to collapse
Well when the screen is about 35% brightness. And I didn't mean the screen is draining battery. I meant when I am actually using the tablet its draining battery faster. I already flashed another rom and its the same. 3mv when its unplagged and 4 mV when its near charged...Do you thing I should flash the official image? I bought it from Tesco in the UK. Will I have a problem changing it?
Edit: Is it possible that the voltage reading is correct and the way its displayed is wrong? maybe the kernel reads 4V, but the app displays it as 4 mV? Any kernel experts? Thanks!
My N7 keeps showing 100% even though it's being used. :\ what's going on
Mine looses power when I have it charging lol
Sent from my Nexus 4 @1.72 GHz on Stock 4.2.2
Hi there; this is my first post so please go easy on me.
Bought a Nexus 4 which is my first Android device, but the battery life is bugging the hell out of me. Surely the screen should always be at the top, right? I left it to sleep overnight on a full charge to find that it had shot down to 60% when I woke up at 7 this morning.
I haven't rooted or flashed or anything like that, because as I said, I'm an Android virgin. I have location settings off, only Gmail syncing and the usual push notifications here and there. Nothing too fancy or strenuous.
Any help on how I can go around fixing this? I'm a little afraid to rooting/flashing/ROMs etc, because I've no clue what works best.
Cheers!
If your saying you left the screen on over night, meaning the phone never went into deep sleep.. If you slept for let's say 6 hours and the phones screen was on for that whole time it's normal that it went down to sixty percent battery.
Maybe I'm understanding your post wrong? Btw I cannot see the picture you posted.
Sent from my SGH-T999 using xda app-developers app
Turn off mobile data and lower the screen brightness to 0 during the day. Also disable WiFi when you're sleeping. I also make sure all apps are closed using the app manager button on the far right.
Mine's been fine following this logic.
Oh sorry, I should meant sleeping overnight, whilst I slept cosily in my bed.
I'll reattach the image in a second
Ah, you won't be able to see any links till I've gone past 10 posts. Back in a bit then, ha.
atw1927 said:
Ah, you won't be able to see any links till I've gone past 10 posts. Back in a bit then, ha.
Click to expand...
Click to collapse
lol I see it now.. try performing a reset, android shouldn't be that high.. are you rooted? custom rom/kernel?
Crisisx1 said:
lol I see it now.. try performing a reset, android shouldn't be that high.. are you rooted? custom rom/kernel?
Click to expand...
Click to collapse
This is NOT the answer. His battery in the image has dropped 7%. If he hasn't used the screen much it is perfectly understandable that screen might not be a large percentage of that 7%. As he uses the phone more screen will use a larger percentage of his battery and Android OS will use less.
If he gets to the point where the screen is on for an hour or two and the percentages are still like this then yes there is a problem.
Sent from my Nexus 4 using Tapatalk 2
joshnichols189 said:
This is NOT the answer. His battery in the image has dropped 7%. If he hasn't used the screen much it is perfectly understandable that screen might not be a large percentage of that 7%. As he uses the phone more screen will use a larger percentage of his battery and Android OS will use less.
If he gets to the point where the screen is on for an hour or two and the percentages are still like this then yes there is a problem.
Sent from my Nexus 4 using Tapatalk 2
Click to expand...
Click to collapse
My android system has never been that high, regardless if I used the phone for 10 minutes or 10 seconds , or not at all.
atw1927 said:
Hi there; this is my first post so please go easy on me.
Bought a Nexus 4 which is my first Android device, but the battery life is bugging the hell out of me. Surely the screen should always be at the top, right? I left it to sleep overnight on a full charge to find that it had shot down to 60% when I woke up at 7 this morning.
I haven't rooted or flashed or anything like that, because as I said, I'm an Android virgin. I have location settings off, only Gmail syncing and the usual push notifications here and there. Nothing too fancy or strenuous.
Any help on how I can go around fixing this? I'm a little afraid to rooting/flashing/ROMs etc, because I've no clue what works best.
Cheers!
Click to expand...
Click to collapse
Actually No the "Screen" should not always be at the top of the stat list. If you use the phone more than it idles, then yes... but if you are like me, mine says "Phone Idle: 20%" (which is on top) and "Screen" is 4th on the list with 12% (Wi-Fi and Cell standby above it) [this is my personal phone, and I mostly use my work phone. hence the high Idle & standby]
I was having an issue with my phone running out of battery, with very little usage from it. I mean very little, I might make 2 calls from it each day, and respond to an email now and then. I found that an App was preventing my Screen from going into "Deep Sleep" or even "Sleeping" possibly. So I uninstalled all apps (well I only had like 4 additional apps installed), except for 2 that I need (Google Voice & Drive). Powered off the phone, charged it fully, then powered back on. Its been running on the same charge for 24+hrs now and reads 68% battery remaining.
So check the apps you have installed, some use background data, and might be causing problems...
Crisisx1 said:
My android system has never been that high, regardless if I used the phone for 10 minutes or 10 seconds , or not at all.
Click to expand...
Click to collapse
And your phone is the definitive guide for what Android OS usage is? Maybe his phone woke up those services for a period of time longer than normal.
The answer of "lol looks wrong root and install kernel" is terrible advice when so little information is given.
Sent from my Nexus 4 using Tapatalk 2
What else would you like to know?
atw1927 said:
What else would you like to know?
Click to expand...
Click to collapse
A longer battery graph would help a lot. If yuppy want top search XDA there is a free app called better battery stats that will help you diagnose if something is running in the background eating battery or even if your phone I'd properly entering deep sleep.
Sent from my Nexus 4 using Tapatalk 2
Better Battery stats and battery screenshots here
atw1927 said:
Better Battery stats and battery screenshots here
Click to expand...
Click to collapse
See now it is much easier to see that you actually do have a problem and what it is. You have the wakelock problem as you can see from Better Battery Stats which falls under Android OS on the other screen. It also appears that you have somewhat weak signal which could cause the wakelock to drain battery even more. There's not much you can do about that wake lock, some kernels have patches for it but those have their own issues as well.
Sent from my Nexus 4 using Tapatalk 2
Could I just install any kernel on stock android and be OK with it? As I've said I've no idea what's best for me; just something nice and clean that doesn't have issues like this. I live onsite where I work so my WiFi is pretty much on all the time if that helps in anyway whatsoever
I'm gonna let it run down completely tonight and charge it, but I don't expect it to help much.
joshnichols189 said:
And your phone is the definitive guide for what Android OS usage is? Maybe his phone woke up those services for a period of time longer than normal.
The answer of "lol looks wrong root and install kernel" is terrible advice when so little information is given.
Sent from my Nexus 4 using Tapatalk 2
Click to expand...
Click to collapse
I never told him to install a kernel. The advice I gave is to do a reset then I asked if he was rooted or running a custom rom or kernel because that might of been the problem.
Sent from my SGH-T999 using xda app-developers app
Bump
Fully charged overnight, battery still sinking like a ship. 45 minutes and I'm already down to 94% already!
Idiot question; will installing a kernel just solve this? For now as a new guy I'd like to keep it as stock as possible before fiddling with it.
atw1927 said:
Fully charged overnight, battery still sinking like a ship. 45 minutes and I'm already down to 94% already!
Idiot question; will installing a kernel just solve this? For now as a new guy I'd like to keep it as stock as possible before fiddling with it.
Click to expand...
Click to collapse
The battery on the n4 seems horrible.
I'm completely stock I just got my phone yesterday, I charged it to 100% now its at 64% battery with only 47 minutes of screen on time.
on the s3 I would be around 83% with 47 minutes of screen on time.
I'm gonna unlock the boot loader and root soon and try Franco kernel I've been reading good things about it.
Sent from my Nexus 4 using xda app-developers app
The battery life on the stock kernel isn't great because the CPU management isn't optimized well. It ramps up the CPU (frequency, number of active cores...) very easily and keeps it there long, which removes the occasional lag but sucks more battery. Flashing a more battery friendly kernel would definitely help you if that is the root of your battery issues and not a badly coded app.
Franco's kernel is a very popular one, and very battery friendly compared to stock (and that doesn't mean you lose performance). It is the one I'm currently using. Most people report of screen on times of 4 or 5 hours. With not so heavy usage and wifi (not 3g) I can also pass 5 hrs.
To install a kernel you need to unlock your boot loader and install a custom recovery. No need to root, but.. why not since you're at it
You can try different kernels with the stock ROM. You don't necessarily need a custom ROM. Just be careful to read the dev's OP and instructions, and definitely not to flash a kernel for another device.
Also another thing that reduces battery is your mobile data, if there are a lot of programs that sync on the background. You can use a program that turns off your mobile data when your screen is off and switch it back on just for a sync every xx minutes. Juice Defender is such app, though I like to use Tasker for that. If you use Tasker and are interested in that project, ask or send me a pm. It works great.