[One (M8) General] Kyuubi10:
Hey Guys, Kyuubi10 back again with a quick guide on improving the battery life of the HTC One M8.

Let's be honest, this phone is getting quite old now. You can already start to feel it lagging, and slowing down. And the battery doesn't last as much as it once used to.

But don't give up hope...your M8 isn't dead yet, and with some good management it can even rival 2016 flagships.

Let's begin with Marshmallow...

If you have not updated your M8 to Android 6.0 yet, WHAT ARE YOU WAITING FOR?

Marshmallow is the best version of Android yet, the efficiency of Lollipop with the Stability of KitKat, and a very fresh take on Battery saving!

Reasons why you should update ASAP:

1 - Lollipop's memory leaks 99% fixed (Don't want to say 100% due to the possibility of some existing out of my limited knowledge, but for all intents and purposes there are no more memory leaks.) This is very important, because the memory leaks were both draining battery life, and slowing down the device...which in turn keeps the screen on longer and wastes even more battery.

2 - Doze!!! It's the latest battery saving feature to be added to Android, and it's basically a SUPER idle state, where the phone if left untouched with screen off for long periods of time will not waste any battery whatsoever! I tested this when going to sleep, phone was in airplane mode, battery saver turned on, screen brightness at minimum...I left it at 100% charge, I woke up it was still at 100%. With airplane mode off, and battery saver turned off the phone lost only 3% battery overnight.

This being said, true battery saving is measured while using the phone right?

It's not about how long it can last without being used, but how long it can last while being used.

But what if you already are on Marshmallow, and your battery life is still not cutting it?

The following solutions are organized from simpler to more complex.

1 - Follow this official HTC guide: Tips for extending battery life. It provides tips on reducing screen brightness, keeping connections off when you're not using them (Wi-Fi, Data, BT, GPS, NFC etc...), lowering volume and vibration strength and using power saver mode.

While their advice is quite obvious stuff, and most of you probably do it anyways, I would like to stress the use of power saver mode when you are out and about away from a convenient power source. Doesn't matter if your battery is at 90%, turn PS mode on, you will barely even feel a difference, but your battery will last you much more than before!

2 - Buy yourself a smartwatch. While it may seem counter-productive to keep Bluetooth on constantly to keep connected to the watch, it actually improves battery life by helping you avoid turning on your phone's screen. At the end of the day the battery saving that comes from it may be equivalent to the drain caused by bluetooth being on, or even greater than the drain. Thus effectively saving you battery life, and being convenient while doing it.

3 - Here comes the big one...ROOT your device and install a custom ROM and Kernel. Just by installing an optimized ROM and optimized Kernel you will get battery savings + better performance. Often you will also have settings you can tweak to optimize battery savings at the cost of performance or vice versa. And with a custom Kernel you can choose one with battery saving CPU governors.

4 - CPU Governors. CPUs, just after your screen, is the second most battery consuming hardware part in your device. Especially since it is on most of the time. Choosing a governor that can make it's job more efficient can save you bucket loads of battery.

The most common one for battery life is called "Conservative", and it will provide you with considerable battery life at the cost of performance. But if you want both good performance and good battery life then you are probably looking for a governor which employs the "Race to Idle" ideology. (If you don't know what it is, do a quick google, it's easy to understand.)

A good option I like to recommend is Wheatley, but if your kernel choice lacks it then interactive will be good enough...but you will have to tweak it's settings yourself to make it most efficient. Couple months ago I created this guide which you may find helpful when tweaking the interactive governor.

5 - Since we have spoken about Rooting then let's start adding some ROOT apps to the mix. Greenify would be my first recommendation.

For 2 main reasons... 1, It helps you stop annoying, battery draining apps which keep themselves running in the background. 2, It's latest versions have included a feature where you can set Doze to start sooner than default. Thus allowing you to reap Doze's benefits earlier and for longer.

Talking about the annoying apps, there's one in particular which comes to mind....Facebook.

Personally, while I don't like it's battery draining, I also don't want to uninstall it...since it's quite useful. Thus in Greenify I found my answer!

6 - Last but not least, if you are noticing unusual battery drainage, but you can't find which app is causing it (or may even be a system app), or if you notice that Doze is not having any effect... it might mean that a wakelock is not letting your device idle for long enough for Doze to start.

For this you will need an app called "Wakelock Detector". Charge your phone to around 80-100% and place it on a desk and let it idle for a couple hours (e.g. When you are asleep). When you are back check what WD found, and it might surprise you. (I found an app called HTC Mode which was keeping my device awake and preventing Doze from starting.)

Another advantage of this app is that once you find the wakelock it links you to Greenify through which you can put that specific app to sleep. Thus preventing it from setting the wakelock again.

If you follow all these steps, you should be able to feel the considerable difference in battery life. Reminding you why you fell in love with this device :)

I hope I have been of help, I noticed that there weren't any Battery Guides specifically made for the M8, so I thought I would leave one here in case anyone is looking for one! :D

If I have helped you make sure to hit that :good: button, I will greatly appreciate it, and you will be helping the community find this guide more easily.

Thanks for reading! Enjoy your longer lasting M8! :D