Hi to all whom read this.
First of all, a note.
This is a guide I have made from my own experience, conducting some tests and using my knowledge as an electrical engineer student. I am not saying this will work for all, as there is no "definate" proof in some of these guidelines, and each individual also uses the phone different. The amount of usage on the phone is of course the major factor to how long your battery cycle life will last. I classify myself as a moderate user, that uses the phone when I have to and when I want to. However I do not use the phone for much browsing or multimedia (except some music on Spotify). So my usage includes a bit of calling, facebook, text messages, calendar usage (mostly for school), active sync, gmail, etc. I some times play Angry Birds if I'm very bored.
This is important! I do want this thread to turn out to be an informative and nice thread, where we can discuss this guide, and come with comments/suggestions. However, I do not want any flaming about the advice in this guide (this includes capslocked statements, especially from people who tend to claim task-killer apps are bad from past experience), and I will not answer questions/posts about task-killer apps. I have conducted tests myself about task-killer apps, and these tests and their results (with explanations) will be written here. Also, I will ask that nobody posts links about "how Android really should be used without task-killer app", as all those links are from programmers perspectives and state all kinds of arguements why the OS does not need a task-killer app. However in this thread, we are discussing battery life. Thus those links are irrelevant! I hereby also state that I understand the Android OS might be self-sufficient in closing apps when it needs RAM, and that SOME task-killer apps will even damage processes and use more battery. However, I am referring to a well designed and well programmed task-killer app that does not do this.
Now that the note is done, here is the actual guide
. By using my phone in the way I describe here, I can easily get 36 hours out of one charge, and still have 15-20% battery left (my power savings mode has not yet started when I charge my phone normally). Thus I estimate I easily could push the phone to 40 hours+.
The first step, the initial conditioning of the battery
Many might know, that modern batteries today are not like old batteries, that needed the cells conditions, so the batter would last long before it needed to be changed out. Back in the old days (Nokia 3310/3330), if one didn't condition the battery, the battery would be useless after 3 months, and you would have to buy a new one. Todays batteries do not need this kind of conditioning to last long (about 1 year). However, from my experience (and also confirmed by other uses here), it is still a good idea to condition new batteries today, as this will give them a long battery cycle life (a cycle life is the time the battery lasts for one charge).
The way to do this, is to let the phone charge the very first time, for at least 8-9 hours. I usually charge it over night. Then the next morning, I try to drain the battery completely by playing with the phone and setting it up. I litterally use the phone until it dies and cannot start up again. Then I will charge the battery again for at least 8-9 hours, and drain it completely again. This process is repeated a third time by me, first then do I consider my battery fully conditioned.
There are rumors/posts/messages from HTC, that say there is a "boost" one can do, that sounds like "charge the battery 8 hours, turn off, then charge one more hour, use it for 3-4 hours, charge it 8 hours again, then turn off and charge one more hour, then battery should last longer". However, I have seen posts that claim this only works for a certain period of time. You are welcome to try this conditioning if you have already used your battery without conditioning it (and do not want to buy a new battery from HTC), but I do not stand by this, as I personally have not tried this out.
Basically the reason you do this, is to "teach" the battery how to handle its cells. By "forcing" it to over charge, it gets an increased capacity in each cell, but this must be done within the first times of charging it, as this is its "learning period". It's important to charge it from completely empty (as it will "learn" that its "dead" and not give out power anymore when it is at that voltage) to completely "overfull" capacity (it will "learn" that it can charge so and so much before refusing to take more). The learning process has to be "repeated" for the battery to take it in fully. Eventhough HTC does state it is a 1200 mAh battery, this can vary according to how you condition it.
Even though at the second and third charge the phone "claims" it's fully charged, the battery can actually take more into it, thus it can be "overcharged" . The phone measures the battery capacity from its voltage, but the cells have an amount of electrons they can take in, that create the current. This (the amount of electrons) is what you are "teaching" the cells, to increase their electron capacity. As the cells become depleted of electrons, the voltage also drops over the battery, thus the phone can measuse its capacity this way (the drops of voltage is SMALL. We are talking drops in milivolts, but it is still measurable by the phone).
The set up of the phone - settings and usage
The next important thing to do, is to set up the phone correctly. To be honest, I don't use many demanding widgets. You are free to set this up as you want, but try to do some research and see if the widget you want to use may pull a lot of power. Personally, I have the big weather widget, facebook widget, favorite contact widget, standard weather/clock widget from HTC, two rows of "power control widgets", one for power control (controls wifi, bluetooth, gps, active sync and brightness), and the other for data control (controls Mobile, wifi, autosync and roaming communications). Last one I have, is the GPS widget from HTC.
Other than that, I only have icons for different programs I may use.
As for usage of my phone, I use it for basically 1-2 hour each day (checking screen "on-time" is about 3hours give or take 30 min after 2 days of usage). I listen to about 30 min - 1 hour of music a day, and use my phone as I want to for checking facebook and writing sms. Gmail comes automatically, and I check my calendar maybe 3-4 times a day. Data communications (mostly 3g/H) are constantly on, and I do not use wifi a lot. GPS is never on during this test.
As for settings, I use a still background image for my homescreen, use the default sound set from HTC and the standard HTC scene.
Bluetooth settings, wifi settings, call settings and sound settings I will not go into as users set them up themselves and they do not affect battery life. Any other options not mentioned I have not changed from stock.
Now come some "settings" I have set:
1) I have turned off "Always-on mobile data". It states on some networks if can use more power, but if a communication is constantly on when a communication is allowed, that in my view will pull some power always. This option is deactivated in: Home screen -> menu button -> Setting -> Wireless & networks -> Mobile networks -> bottom option "Enable always-on mobile data. This will mean that sometimes your "active" connection will be shut down, until it's needed again. However, this does not deactive Active Sync
2) I have set my display brightness down to about 1/5 of the slide, and thus disabled automatic brightness. This is changed in: Home screen -> menu button -> Settings -> Display -> Brightness. Auto-rotate is enabled under "Display" setting.
3) I have set up these active sync accounts in the settings under "Accounts & sync": Facebook (no frequency setting), Facebook for HTC sense (updates once a day), Google (not updating contacts, but calendar and gmail), HTC sense (Not update when opened, and update schedule is "as items change (push)") and weather (update schedule every hour). News and stocks I have deactivated
4) I have "Use wireless networks" and "phone finder" enabled under the settings "Location". The others are disabled.
5) Under "Privacy" option I have enabled "Back up my settings", but not automatic restore (however, this must be enabled if you have had the funny "sms disappear" problem and you have back ups on HTC sense).
6) Default connection type to PC is HTC sync, but it asks me every time I have enabled under the settings "Connect to PC"
7) Power saver is enabled, engages at 15%. It all options are enabled in the settings section, and the screen brightness gets lowered to minimum. Screen time out is set to 30 seconds.
8) Under the "Applications" setting I have both options (Unknown sorce and fast boot) enabled, and under "Development" only USB debugging is on. The other two sections I will not go into, as the user themselves manages these.
This is basically how I have set up my phones settings.
The very discussed, but power saving task-killer app (aka. ATK)
Here comes what many people disagree on about battery life. However, I decided to conduct my own test with my DHD to see what was correct (at least for me).
One day I started not using my task-killer app. I charged my phone all the way up, and used it normally. In 4 hours with a "screen on" time of about 15 min, 50% of my battery was eaten up, and over 50% of the battery used had been taken by "Android OS". So this didn't seem to bright. However, I decided to give it a chance. By the evening my phone was fully charged again. While still in the charger, I uninstalled my ATK (as some people claim you have to do for this to work, as some ATKs take a lot of power), rebooted the phone and started using my phone normally. I had a 30 min call, then went to bed after starting up all my normal apps. The next morning only 12% battery had been used, and I was positively surprised. However, as the day progressed, the battery was getting more and more drained. I figure this is from the RAM programs that had been opened were using, as I had been using the phone during the day. From not being on the list in the morning, "Android OS" went up to 40% usage and tied with the "Display" on battery used. The display had an on-time of about 1 hour from the whole day. By the evening (basically 22 hours after I unplugged) I had to reconnect my phone as it was on less than 10% battery left. After this, I have continued this set up for a few days now, and only today I went back to my original set up. The result was, that as each day went (without a reboot), the faster my battery seemed to be eaten up in the start until it became stable. I guess this is because most of my RAM was used at this point, meaning Android was killing processes if I needed more. The last 2 days I've had a battery life of about 20 hours give or take.
Today, when my phone was unplugged since yesterday evening (around 1800), I had about 20% battery remaining at around 1500. With the current "drain", I estimated my battery would die within a couple of hours. I installed my ATK again, ran it. Now 3 hours later, my battery has only dropped 5%, without a reboot. All the ATK did was kill processes and free up RAM. I haven't changed anything else.
As you can see, for me, the results are conclusive with my ATK ("Advanced Task Killer" by ReChild, the one and only that I recommend, as this is programmed to ignore vital system processes, and other processes that Android will automatically restart, thus it does not fight with the OS and drain battery. This ATK does not use much CPU power either from what I gather, although I have not checked the numbers myself). I gain quite a bit of battery life by using a ATK.
As for "Android OS", my theory is that this is the power used by programs running in the OS. This can include CPU power usage, system process usage, and RAM usage. While I used ATK actively, "Android OS" never got over 5% usage of the battery. While conducint my test without ATK, "Android OS" never got under 40% of battery used at the end of a battery cycle life.
The reason I am precising the "reboot", is because a "restart" (the bottom option when holding the power button down) will reboot/start over the phone, and dump its RAM memory. This RAM memory is used by both the OS, and programs that are started up on the phone, even though the programs might be inactive, they are in the RAM pulling power constantly. Even though this power pull is small, over time it becomes significant on such a small battery the DHD has.
Here is a quote from what I wrote about ATKs earlier, countering a so called "why you shouldn't use a ATK link". The quotes inside the quote is from comments of the article, link here.
This is from another post by me, explaining how RAM works if anybody wonders why it constantly pulls power.
This was basically my comprehensive guide. I know it is long, and gonna be tideous to read through, but I hope it is worth it for people. I certainly had fun writing this and conducting the test.
Please feel free to post questions and comments about this guide, and I will answer as best as I can. Further tips to increase battery life are also welcome. However the note statements in the start apply, please follow them so we get a nice clean thread, and behave. Show respect, then people will be nice to you back 
First of all, a note.
This is a guide I have made from my own experience, conducting some tests and using my knowledge as an electrical engineer student. I am not saying this will work for all, as there is no "definate" proof in some of these guidelines, and each individual also uses the phone different. The amount of usage on the phone is of course the major factor to how long your battery cycle life will last. I classify myself as a moderate user, that uses the phone when I have to and when I want to. However I do not use the phone for much browsing or multimedia (except some music on Spotify). So my usage includes a bit of calling, facebook, text messages, calendar usage (mostly for school), active sync, gmail, etc. I some times play Angry Birds if I'm very bored.
This is important! I do want this thread to turn out to be an informative and nice thread, where we can discuss this guide, and come with comments/suggestions. However, I do not want any flaming about the advice in this guide (this includes capslocked statements, especially from people who tend to claim task-killer apps are bad from past experience), and I will not answer questions/posts about task-killer apps. I have conducted tests myself about task-killer apps, and these tests and their results (with explanations) will be written here. Also, I will ask that nobody posts links about "how Android really should be used without task-killer app", as all those links are from programmers perspectives and state all kinds of arguements why the OS does not need a task-killer app. However in this thread, we are discussing battery life. Thus those links are irrelevant! I hereby also state that I understand the Android OS might be self-sufficient in closing apps when it needs RAM, and that SOME task-killer apps will even damage processes and use more battery. However, I am referring to a well designed and well programmed task-killer app that does not do this.
Now that the note is done, here is the actual guide
. By using my phone in the way I describe here, I can easily get 36 hours out of one charge, and still have 15-20% battery left (my power savings mode has not yet started when I charge my phone normally). Thus I estimate I easily could push the phone to 40 hours+.The first step, the initial conditioning of the battery
Many might know, that modern batteries today are not like old batteries, that needed the cells conditions, so the batter would last long before it needed to be changed out. Back in the old days (Nokia 3310/3330), if one didn't condition the battery, the battery would be useless after 3 months, and you would have to buy a new one. Todays batteries do not need this kind of conditioning to last long (about 1 year). However, from my experience (and also confirmed by other uses here), it is still a good idea to condition new batteries today, as this will give them a long battery cycle life (a cycle life is the time the battery lasts for one charge).
The way to do this, is to let the phone charge the very first time, for at least 8-9 hours. I usually charge it over night. Then the next morning, I try to drain the battery completely by playing with the phone and setting it up. I litterally use the phone until it dies and cannot start up again. Then I will charge the battery again for at least 8-9 hours, and drain it completely again. This process is repeated a third time by me, first then do I consider my battery fully conditioned.
There are rumors/posts/messages from HTC, that say there is a "boost" one can do, that sounds like "charge the battery 8 hours, turn off, then charge one more hour, use it for 3-4 hours, charge it 8 hours again, then turn off and charge one more hour, then battery should last longer". However, I have seen posts that claim this only works for a certain period of time. You are welcome to try this conditioning if you have already used your battery without conditioning it (and do not want to buy a new battery from HTC), but I do not stand by this, as I personally have not tried this out.
Basically the reason you do this, is to "teach" the battery how to handle its cells. By "forcing" it to over charge, it gets an increased capacity in each cell, but this must be done within the first times of charging it, as this is its "learning period". It's important to charge it from completely empty (as it will "learn" that its "dead" and not give out power anymore when it is at that voltage) to completely "overfull" capacity (it will "learn" that it can charge so and so much before refusing to take more). The learning process has to be "repeated" for the battery to take it in fully. Eventhough HTC does state it is a 1200 mAh battery, this can vary according to how you condition it.
Even though at the second and third charge the phone "claims" it's fully charged, the battery can actually take more into it, thus it can be "overcharged" . The phone measures the battery capacity from its voltage, but the cells have an amount of electrons they can take in, that create the current. This (the amount of electrons) is what you are "teaching" the cells, to increase their electron capacity. As the cells become depleted of electrons, the voltage also drops over the battery, thus the phone can measuse its capacity this way (the drops of voltage is SMALL. We are talking drops in milivolts, but it is still measurable by the phone).
The set up of the phone - settings and usage
The next important thing to do, is to set up the phone correctly. To be honest, I don't use many demanding widgets. You are free to set this up as you want, but try to do some research and see if the widget you want to use may pull a lot of power. Personally, I have the big weather widget, facebook widget, favorite contact widget, standard weather/clock widget from HTC, two rows of "power control widgets", one for power control (controls wifi, bluetooth, gps, active sync and brightness), and the other for data control (controls Mobile, wifi, autosync and roaming communications). Last one I have, is the GPS widget from HTC.
Other than that, I only have icons for different programs I may use.
As for usage of my phone, I use it for basically 1-2 hour each day (checking screen "on-time" is about 3hours give or take 30 min after 2 days of usage). I listen to about 30 min - 1 hour of music a day, and use my phone as I want to for checking facebook and writing sms. Gmail comes automatically, and I check my calendar maybe 3-4 times a day. Data communications (mostly 3g/H) are constantly on, and I do not use wifi a lot. GPS is never on during this test.
As for settings, I use a still background image for my homescreen, use the default sound set from HTC and the standard HTC scene.
Bluetooth settings, wifi settings, call settings and sound settings I will not go into as users set them up themselves and they do not affect battery life. Any other options not mentioned I have not changed from stock.
Now come some "settings" I have set:
1) I have turned off "Always-on mobile data". It states on some networks if can use more power, but if a communication is constantly on when a communication is allowed, that in my view will pull some power always. This option is deactivated in: Home screen -> menu button -> Setting -> Wireless & networks -> Mobile networks -> bottom option "Enable always-on mobile data. This will mean that sometimes your "active" connection will be shut down, until it's needed again. However, this does not deactive Active Sync
2) I have set my display brightness down to about 1/5 of the slide, and thus disabled automatic brightness. This is changed in: Home screen -> menu button -> Settings -> Display -> Brightness. Auto-rotate is enabled under "Display" setting.
3) I have set up these active sync accounts in the settings under "Accounts & sync": Facebook (no frequency setting), Facebook for HTC sense (updates once a day), Google (not updating contacts, but calendar and gmail), HTC sense (Not update when opened, and update schedule is "as items change (push)") and weather (update schedule every hour). News and stocks I have deactivated
4) I have "Use wireless networks" and "phone finder" enabled under the settings "Location". The others are disabled.
5) Under "Privacy" option I have enabled "Back up my settings", but not automatic restore (however, this must be enabled if you have had the funny "sms disappear" problem and you have back ups on HTC sense).
6) Default connection type to PC is HTC sync, but it asks me every time I have enabled under the settings "Connect to PC"
7) Power saver is enabled, engages at 15%. It all options are enabled in the settings section, and the screen brightness gets lowered to minimum. Screen time out is set to 30 seconds.
8) Under the "Applications" setting I have both options (Unknown sorce and fast boot) enabled, and under "Development" only USB debugging is on. The other two sections I will not go into, as the user themselves manages these.
This is basically how I have set up my phones settings.
The very discussed, but power saving task-killer app (aka. ATK)
Here comes what many people disagree on about battery life. However, I decided to conduct my own test with my DHD to see what was correct (at least for me).
One day I started not using my task-killer app. I charged my phone all the way up, and used it normally. In 4 hours with a "screen on" time of about 15 min, 50% of my battery was eaten up, and over 50% of the battery used had been taken by "Android OS". So this didn't seem to bright. However, I decided to give it a chance. By the evening my phone was fully charged again. While still in the charger, I uninstalled my ATK (as some people claim you have to do for this to work, as some ATKs take a lot of power), rebooted the phone and started using my phone normally. I had a 30 min call, then went to bed after starting up all my normal apps. The next morning only 12% battery had been used, and I was positively surprised. However, as the day progressed, the battery was getting more and more drained. I figure this is from the RAM programs that had been opened were using, as I had been using the phone during the day. From not being on the list in the morning, "Android OS" went up to 40% usage and tied with the "Display" on battery used. The display had an on-time of about 1 hour from the whole day. By the evening (basically 22 hours after I unplugged) I had to reconnect my phone as it was on less than 10% battery left. After this, I have continued this set up for a few days now, and only today I went back to my original set up. The result was, that as each day went (without a reboot), the faster my battery seemed to be eaten up in the start until it became stable. I guess this is because most of my RAM was used at this point, meaning Android was killing processes if I needed more. The last 2 days I've had a battery life of about 20 hours give or take.
Today, when my phone was unplugged since yesterday evening (around 1800), I had about 20% battery remaining at around 1500. With the current "drain", I estimated my battery would die within a couple of hours. I installed my ATK again, ran it. Now 3 hours later, my battery has only dropped 5%, without a reboot. All the ATK did was kill processes and free up RAM. I haven't changed anything else.
As you can see, for me, the results are conclusive with my ATK ("Advanced Task Killer" by ReChild, the one and only that I recommend, as this is programmed to ignore vital system processes, and other processes that Android will automatically restart, thus it does not fight with the OS and drain battery. This ATK does not use much CPU power either from what I gather, although I have not checked the numbers myself). I gain quite a bit of battery life by using a ATK.
As for "Android OS", my theory is that this is the power used by programs running in the OS. This can include CPU power usage, system process usage, and RAM usage. While I used ATK actively, "Android OS" never got over 5% usage of the battery. While conducint my test without ATK, "Android OS" never got under 40% of battery used at the end of a battery cycle life.
The reason I am precising the "reboot", is because a "restart" (the bottom option when holding the power button down) will reboot/start over the phone, and dump its RAM memory. This RAM memory is used by both the OS, and programs that are started up on the phone, even though the programs might be inactive, they are in the RAM pulling power constantly. Even though this power pull is small, over time it becomes significant on such a small battery the DHD has.
Here is a quote from what I wrote about ATKs earlier, countering a so called "why you shouldn't use a ATK link". The quotes inside the quote is from comments of the article, link here.
This is from another post by me, explaining how RAM works if anybody wonders why it constantly pulls power.
This was basically my comprehensive guide. I know it is long, and gonna be tideous to read through, but I hope it is worth it for people
. I certainly had fun writing this and conducting the test.Please feel free to post questions and comments about this guide, and I will answer as best as I can. Further tips to increase battery life are also welcome
. However the note statements in the start apply, please follow them so we get a nice clean thread, and behave. Show respect, then people will be nice to you back 
