[Droid Incredible General] kaze06:
In the DInc forum more than probably any other forum on XDA, there is a copious amount of battery life related threads. How to extend your battery life, what kernel is best, what ROM is best, what extended batteries work, what applications will help, combinations of CPU and brightness, all kinds of jazz. Truth be told, most people who have come to a "solid conclusion" about what is best for their battery life are misleading themselves, and others. Why? Well..

#1. There are too many variables.

Your average joe who posts on here claiming they got XX amount of battery life compared to average joe number two's claim of getting YY hours tells no one anything. The fact of the matter is that in these phones, there are SO many things that act as variables on battery life that most people don't even consider. The obvious ones are data usage, WiFi connectivity, screen brightness, and CPU clocks to name a few. But what a lot of people don't consider are things like signal strength. My battery life personally is bad through the week because my school has absolutely terrible service. My battery life triples throughout the day with Airplane Mode on and WiFi enabled. It's well known in the cell phone consumer society that the better your signal is, the easier your radio will be on your battery. If you're teetering on very poor service, or none at all, your radio is constantly searching for signal so it can get you back on the network as soon as possible. This also applies to the WiFi radio. Some people leave theirs on all the time, some don't. Same for Bluetooth, GPS, anything. There are too many variables for your average person to cover to be able to accurately claim that "this app" or "this ROM" or "this method" does exactly "this" to your battery life.

#2. You're probably undereducated about how your battery works.

Don't get me wrong on this one, we have a lot of very intelligent people here at XDA, many far more intelligent than I, that keep this place rolling on a daily basis, but far too many of the people who try to make factual claims about battery life don't know what they're talking about. The most prolific example of this is the argument between total discharges, and interval charging. There are people who argue that allowing your battery to completely discharge and then charge back to full is the best way to preserve battery life. Then there are some who are adamant about charging whenever a charger is present, regardless of battery percentage. While very few of us here, myself included, are battery technicians or something of the sort, there is factual data to support the idea that Lithium Ion batteries do not have any sort of memory like NiCad and other batteries do. While this may be true, on the other hand, fully charging and discharging your phone allows it to more accurately determine what voltage your battery is producing and thus gives a better percentage reading. Your battery life percentage on your phone is no clear indicator and is nothing more than the phone's mathematical way of processing the output of the battery and translating it into a more useful term for people like you and I. This is why wiping battery stats and completely draining a fully charged battery seems to help with battery life, because you won't see as many violent drops in percentage because the phone can more accurately calculate the power usage. That being said, wiping battery stats does nothing more for you than that. It does not magically make your battery superpowered and won't make dinner for you.

#3. All batteries are different.

Extended batteries are an interesting thing. You can buy two of the same make and model from the same place, and the two batteries can perform completely differently. This is because no two batteries are the same. Quality control issues, differences in materials, shelf life, production date, and all kinds of other factors go into how well a battery will perform. Some people get great experiences from the $10 eBay batteries and some get experiences worse than stock. Some people see quadrupled life out of OEM extended batteries, and some see minimal gains. This also applies to the stock battery that comes with the phone. That being said, mAh ratings are also relative and not all batteries live up to their true claims. A battery said to operate at 2500 mAh may not ever reach that capacity and it may run at a true value of 2000 mAh. The case will rarely ever be reversed, but you see the point. Take battery specifications with a grain of salt, because you aren't always going to get what you pay for.

#4. All phones are different.

The hardware in your phone may or may not be the same as the hardware in my phone, and one of the biggest differences in the DInc with this respect is the SLCD and AMOLED screens. AMOLED screens can save or expel more battery than SLCD screens depending on what you are viewing. A person with an AMOLED who uses primarily dark-themed apps and a dark background may see better life than someone identical who uses light-themed apps and a lighter background. Not to mention that all of the hardware in these phones aren't identical and sometimes parts slip through with lower efficiencies or defects that may or may not affect your battery life, and you will likely never know.

#5. ROMs/Kernels behave erratically.

The Warm Z ROM I use on my phone might deliver totally different results for you than it does for me. Same goes for kernels. We have found time and time again that kernel and ROM changes are not universal for battery life and everybody gets different experiences. You have to try out what fits you, and if you're that interested in finding the perfect balance, you'll just have to try them all. That's a long, painstaking process, but there's no solid evidence to tell you what will be optimal for your setup.

Now...

All that being said, I want you to understand I am not bashing anyone who tries to make a good conclusive result for how to improve battery life. Some methods are common sense and surefire, and some are wives tales. There are some great threads on battery life and topics related to it, two of which I will link to here:

Effects of CPU Frequency and Screen Brightness on Power Consumption

Your Battery Gauge Is Lying To You

These are both by XDA Member byrong, and he uses principles of science and the scientific method to make conclusive data in relation to battery life and how certain variables affect it. He eliminated as many variables as possible in his study and produced linear data that coincides with common sense ideas relating to smartphones and battery life. Note he does not make claims of how long your battery will last, or what kind of effects to expect from each setting, but he produces solid data that allows you to make your own interpretation.

At the end of the day, battery life boils down to balancing out functionality for conservativeness. If you're the kind of person who doesn't need auto sync'ing and push notifications, then by all means disable those things and keep your phone alive a little longer. If you're always by a charger throughout your work day, leave it all on! It's all preference, and there is no solid set method to making your battery all it can be. No ROM, kernel, app, wipe, or other method is going to be the 'be-all-end-all' of battery life extension. Simply see what works for you, and take your own results with a grain of salt. If you test one method one day, and another one the next, and you see that method A gave you 4 more hours than method B, take into account that you were driving through an area with no signal on your way home from work during the usage of method B, or you were playing a game on method B or you did less browsing on method A. Keep your trials as scientific as possible if you want to get real solid results.

Above all, just use your phone and enjoy it. If you never go more than 12 hours without being around a charger, and your phone lasts 15 hours, there's no real purpose in trying to sacrifice more things you use and enjoy to try and get a bigger and better number. Charging a phone, even just a little bit, doesn't take forever, and you can get a valuable amount of juice out of 15 minutes on the plug. Use common sense and don't overthink it. Everybody uses something a little different. That's why we have these phones, because we all want something a little different.