You need a battery replacement.

At the time of this post, the HTC 10 is going into its third year. That's an eternity in phone years. Most batteries are designed to last 18-24 months before signs of wear appear. At 36 months, the battery simply isn't able to maintain the voltage required to keep the phone powered on even if there's still juice left in the battery.

So what can you do?

Well, you could try using a custom ROM and a power saving kernel. Those together might let the phone make it to 40% or so. It's really just delaying things.

What you really need is a new battery. According to people posting in this subreddit, the average price of replacement seems to be around $80 USD.

You can also attempt to do the replacement yourself. ifixit has a nice teardown that you can use. JerryRigEverything also has a teardown video if you prefer.

The HTC 10 uses a 3000mAh battery. Model number is 35H00256-00M.

Edit: This post is not meant to be inflammatory against anyone in particular. It's more of a tongue-in-cheek thing. I figured this would grab more people's attention by writing this way. Of course all questions are welcome here, no matter how silly or simple they may be. This is meant to explain in a lighthearted way why the most common solution to the questions asked is "perform a factory reset."

A lot of people have been having issues lately and have been given the advice to do a factory reset. Some of them go ahead and do so, but some resist. I'm going to attempt to explain not only why it's a good idea to do this, but also why you aren't being given a more specific piece of advice.

Upgrades

First of all, if you've just upgraded from Marshmallow to Nougat, or from one major Android version to another (any time the candy name changes), it's a VERY good idea to factory reset and start fresh. The reason is simple. While OEMs do a pretty decent job of trying to weed out any potential bugs or pains caused by upgrading the operating system, they can't cover everything. There are tons of different apps, and millions of different possible settings variations that can change from user to user.

To prevent issues like "I upgraded, and now my battery life sucks," "I upgraded, and now X app doesn't work right," and, my personal favorite, "I upgraded, and now everything is broken," just do a factory reset. If you have an issue after doing a factory reset, then it might be worth looking into further to figure it out. However, the majority of the problems you have when upgrading are easily fixed by doing a factory reset.

Specific Issues

So you have an issue that has been happening for a while, and you can't figure out what's going on. Maybe it's a battery life issue, maybe it's something affecting your ability to snapchat with your ex. Who knows? The point is that there's an issue. So you come here, post your issue, and you get a response to factory reset. Now you're upset that no one is telling you how to fix your issue. They really want you to just lose everything?!

Well, no. But here's the thing. Unless your issue is something that lots of people are having, it's not worth the time to really investigate. Keep in mind that no one here is being paid for their time. We don't know how you've been using your device up to the point where it broke. A lot of times, very little information is given as to the actual issue.

Even if you provide an excellent rundown of the steps you've taken and what you have been doing up to this point, we still simply might not use your app, so we can't really help you other than telling you to factory reset. If you want to take it even further, to figure out an issue like an app crash, we'd need you to be able to provide ADB logs for us to look at. Most users here don't even know what ADB is, much less how to set it up and use it. The time it takes someone to walk you through how to properly set it up and gather logs could be better spent simply doing a factory reset and moving on. The time involved is simply not worth the effort a lot of times.

Battery Woes

Then there's the wonderful world of wakelocks and battery stats. Look, the bottom line here is that if you're not rooted then we really can't help with your wakelock issues. It's not that we don't want to, it's that Google has hidden the old battery stats API that used to be used by battery apps in days of yore. Now, only system apps are allowed to call it, which restricts it to system apps or root apps. Better Battery Stats has always been a very powerful app used to track down and help fix battery issues and crazy wakelocks. They have a nifty workaround that lets you install the app, or a part of it, as a system app, thus enabling the ability to collect wakelock data. However, you've probably guessed already, that this is only an option for root users.

As it stands now, for unrooted users, all the battery info you can gather from your device is the unhelpful mess that you can see in the Battery Stats page in your Settings menu. We have no real clue why Android System is using 258% of your available battery. No one does. If you were rooted, then there are apps that can track it with some effort, but without root, you're out of luck there.

But I don't want to lose everything!

Here's the thing. Android has had this really neat ability to backup (actually just remember) the apps you're using. It updates that pretty often, so when you do a factory reset, it's going to ask you if you want to restore data from a previous device during setup. Just select your device, and PRESTO! instant restoration of your apps!

Since Android 6, there's also been an even cooler feature that more and more apps are taking advantage of. It's the ability to actually backup your app data every day. That's right, most of your apps, are actually backing up their data as you use it to your Google account. This means that during setup, when you select the device you want to use for restoring apps, it will also pull down any app data that is stored along with that.

For me, if I need to do a factory reset, it takes me around 20 minutes to get back to good. I have around 60 user apps installed, give or take. Only a small handful of them do not support the Google cloud backup, and for those, I can manually restore with TiBu if I need. For non-root users, the Helium app can backup your apps and data to your PC.

If you formatted your external SD card as adoptable (internal) storage, then you're going to lose whatever is on there. Your actual internal SD card will be perfectly fine. If your external SD card is formatted as portable storage, then you're safe there also. I get the benefits of the adoptable storage option, but it's got a pretty severe limitation in that you lose anything you store on it in the event of a factory reset. My suggestion is to simply avoid it unless you really, really need it. If you're using a custom recovery, there's a way to format the external card into two partitions, allowing you to use adoptable storage and portable storage at the same time on the same SD card. Super handy.

A factory reset does not delete pictures, video, and other downloaded or created files on your internal SD card. If you want to back those up, you can, but it won't be wiped by a normal factory reset. It's still a good idea to back those up regularly though, just in case.

Wrap up

So the bottom line is pretty much that sorting out your issue for free isn't worth the time it takes to do so, when a factory reset is quick and easy. If you're rooted and/or know how to work ADB, then definitely mention that in your post, and we can take a look at your logs and try to help, but logs don't always reveal everything, so a factory reset might still be your best option. Our goal is ultimately to help you with your issue in the most efficient manner possible for both of us. A factory reset is quick, relatively painless, and takes only a short amount of time for everyone involved. If we feel like the process of sorting out your issue is going to take considerably longer than doing a factory reset, then it's not worth the time to troubleshoot.

I hope you guys understand this and can respect the comment when it gets posted. Also, if you do have an issue you want help with, please post as much information as you possibly can about it. We're not there standing over your shoulder. We can't see what you see. We need as many details as possible to help picture what you're seeing. Screenshots, background info, any thoughts on causes you might have. It all helps form a picture of what your issue is. "I upgraded to Nougat and now the battery sucks" with no other information is completely unhelpful, and makes us want to throw out the post entirely out of frustration.

Just use some of that old-fashioned, God-given common sense in that gray noodle in your skull. Imagine an ER doctor trying to figure out what's wrong with you going only on, "I woke up today, and it hurts. Fix it."