A definitive guide to everything that affects smartphone battery life

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You’ve no doubt seen or read many articles online about saving battery life. It’s a popular topic because nobody likes tethering a phone to the wall multiple times a day. However, most such articles give you ideas about what to try in order to improve your battery life. This time around, we’re instead going to identify all of the various things that cause drain battery. Here’s our definitive list of everything that has the potential to affect your smartphone’s battery life.

The list is actually surprisingly long and that’s probably a good indicator of why so many people struggle with battery life. However, when looked at in greater detail, everything can be easily packed into either hardware or software problems. You can use this list to determine what might be messing up your battery and then take the proper steps to try to fix it.

Battery size

Galaxy Club

We’ll start with the most obvious influence on battery life — the size of the battery itself. Not all smartphones have the same battery size and it’s this size that helps determine how long your phone will go before hitting zero. Smartphone batteries are generally measured in milliamp hours (mAh). This is mostly simple math. The more mAh a phone has, the longer it should be able to theoretically last. It doesn’t always work that way, but it’s a good place to start.

On the high end, flagships like the Samsung Galaxy Note 10 Plus and Huawei Mate 30 Pro come with gargantuan 4,500mAh batteries. Meanwhile, smaller devices like the Pixel 4 (not XL) come with only 2,800mAh. Most of the battery life heavyweights have larger batteries rather than smaller ones.

There are a ton of things that correlate with battery life. However, if you ignore other variables, the phone with the biggest battery will go the longest period of time between charges.

Display

There are four different ways a display can affect battery life. The first is the size, as larger screens have more surface area and require more power to light up. Of course, phones with larger displays also usually have larger batteries so there is a bit of a give and take there.

The second way a phone’s display affects battery life is the resolution. Admittedly, the differences aren’t huge, but it is objectively measurable. Displays with 1440p resolution have 77% more pixels than a 1080p display and it requires extra processing power (and therefore, more battery) to render those extra pixels. OEMs sometimes include a 1080p mode on a 1440p display to help cut back on the processing power and save battery.

Displays use the most battery by far. They are the centerpiece of every smartphone.

Brightness is another significant power draw. This is also a matter of simple deduction. The brighter something is, the more power it requires. That said, going from 50% to 40% brightness is a fairly negligible difference compared to going from 80% to 20%.

Finally, the display’s refresh rate matters a lot. The refresh rate represents the number of times a screen refreshes every second and is measured in hertz (Hz). Some newer phones have 90Hz and 120Hz displays which refresh 50%-100% more frequently than regular 60Hz displays. That requires a whole bunch of extra processing power and put further strain on your phone’s battery.

Related: 90Hz smartphone display test: Can users really feel the difference?

Displays eat up more battery than any other individual component of a device because it is the main way we interact with a phone. This is why most battery saving tricks revolve around display tweaks. However, lowering your brightness a few percentage points does virtually nothing and the resolution only matters if you use your phone constantly. Finally, using dark themes on AMOLED displays doesn’t work like most think it does.

Connections

Connections have a massive impact on battery life. The most common connections are your cell phone signal, data, Bluetooth, Wi-Fi, and location services. Connections drain battery in a few different ways and the first one is fairly obvious. If you enable these connections and don’t use them, they draw unnecessary power over the course of the day. Hardware and software optimizations have minimized this drain and it’s not as bad as it used to be, but it’s still a factor.

Additionally, a weak signal can greatly increase battery drain. This one is often difficult to fix. Your device regularly checks for signal strength. When the reception is bad, the phone checks more frequently and this constant checking drains the battery. Usually, this only happens in certain types of buildings and in bad reception areas, but if you live (or work) in one of those places, it can be a constant and nearly unsolvable problem.

Every time your phone connects to something, it costs you battery life.

Finally, actually using these connections drains your battery. If you go online and spend five minutes downloading a file, that’s five whole minutes your phone is actively using its networking hardware. The same is true of voice calls as your phone engages its radio for the entire length of the call.

A lot of people recommend using airplane mode to switch off all connections when not using your phone. To be honest, it doesn’t save that much battery and it ends up being invasive and annoying. We recommend staying connected to Wi-Fi while at home (or work) and setting your apps to update, backup, or download new stuff while your phone is on a charger. Otherwise, just leave your Bluetooth and GPS off when you’re not using them.

Chipset

The chipset matters more than probably anything else here because it basically runs the whole phone. There are many ways a chipset can impact battery, especially if you toy with the clock speed, CPU governors, and voltage. However, you can’t mess with those things without root and most people don’t dabble in rooting.

For regular users, the first thing that matters for the chipset is its generation. Every year chips get smaller, faster, and more energy-efficient. The Snapdragon 855 was faster and more energy-efficient than the Snapdragon 845, and the latest Qualcomm chipset, the Snapdragon 865, will no doubt represent another leap forward. The same goes for Huawei’s Kirin SoCs, Samsung’s Exynos chips, and MediaTek‘s silicon. This is a rather complex topic, but the super basic explanation is that newer chipsets can do the same work as older chipsets except faster, with less energy consumption, and with less heat. All of those things affect battery life.

An upgraded chipset is a lot more important than a lot of people realize.

The model of the chipset matters as well. The Pixel 3a XL was one of the big surprises in terms of battery life in 2019. Part of that was due to the Snapdragon 670, a less powerful chip tuned for battery life rather than performance like the Snapdragon 855. On the other end of the scale, the Snapdragon 855 Plus is an overclocked version of the regular 855 and it uses more power.

Chipset updates get frequently overlooked when talking about new smartphones because a lot of people only look at raw performance. However, the efficiency, size, and heat improvements are arguably more important than raw performance boosts these days.

Camera

The camera is one of the most important pieces of hardware on a phone. However, it also has the capacity to drain the battery quite a bit. The first and most obvious reason is that it is a separate piece of hardware. It needs power to function, especially if it has moving parts like Samsung’s multi-aperture cameras or the motorized front camera of newer OnePlus phones.

However, the vast majority of camera battery drain comes from display and processor usage. Your display is needed as a viewfinder and some OEMs even bump up the brightness of the display when in camera mode. Additionally, every modern smartphone has at least some post-processing and that also requires extra processing power. This is further amplified by unique camera features like LG’s triple shot on the LG V40 or Night Sight on Pixel devices.

People who use the camera excessively often have below average battery life.

Video is even more battery intensive. The processor has to take anywhere between 30 and 60 photos per second depending on the frame rate of the video and it also has to eventually stitch all of them together. Of course, resolution matters here as well as many cameras can shoot in 4K resolution which is even harder on the processor and, thus, even harder on the battery.

Shutterbugs drain their batteries a lot more quickly than people who don’t use their camera very often. Additionally, apps with a heavy reliance on the camera, like Snapchat, may lead to greater battery drain with prolonged use because of their excessive use of the camera.

Other hardware

iFixit

Basically any piece of hardware on a phone drains the battery to some extent while in use. There are a ton of examples. Google’s Soli chip on the Pixel 4 series phones is always on and awaiting your hand signals. The original Moto X had a separate processor core that was always working to listen for your voice commands. Not only does this extra tech cause more battery drain, but its inclusion may also lead to smaller batteries due to space limitations.

There are other factors too that affect every phone. You wouldn’t think a vibration motor would cause that much battery drain. However, if you’re one of those people that gets hundreds of notifications per day, that is hundreds of times that vibration motor runs.

Think about it, how many times does your phone vibrate or make noise per day? Per week? Per year? It adds up over time.

The same goes for speakers. Every time you watch a video, listen to music, leave your notification tones on, or use the phone for a phone call. You can save some battery by keeping everything on mute, but where’s the fun in that? Sometimes the effect on the battery isn’t much, but as with all things, the more you use it, the more power it uses.

Generally speaking, the amount of actual drain is directly correlated with how often those things see use. The Pixel 4 XL’s Soli chip can’t drain battery if it’s not on. Additionally, sometimes the power drain is so minimal that it’ll never matter anyway. For instance, Samsung estimates that a full S Pen charge requires 0.5mAh, or about 1/9,000th of the Note 10 Plus battery.

Temperature and Age

Researchgate The ideal temperature to maximise battery cycle life is between 20 and 50°C

Smartphone battery life is heavily affected by both temperature and age. Batteries work best when they are brand new and operating at room temperature. However, because phones heat up during use and time marches on for all eternity, both of these things affect your battery life eventually. In fact, age is the primary reason your battery life gets shorter as your phone gets older.

You shave a second or two off of your phone’s maximum battery capacity every time you charge it. Batteries use chemical reactions to store and process energy and no chemical reaction is infinite. The method has been optimized like crazy, though, and that’s why batteries last as long as they do to begin with. Additionally, batteries lose capacity even if you don’t use them. Popular Mechanics has an excellent article on the matter here.

Leaving your phone in a hot car or using it while charging is really not good for your long term battery life.

Temperature is a bit more tricky. Cold batteries have lower capacities (remember, we’re dealing with chemicals here) while warmer batteries offer better performance. However, too much time spent at extreme temperatures can cause permanent degradation of the battery over time. Battery University states that modern lithium batteries perform most optimally at about 68F. However, most people can’t temperature control their entire life so this problem is more or less unavoidable. The good news, though, is that OEMs have optimized charging and fast charging to an extent where users have few opportunities to really mess things up.

You can use some tricks to help prevent excess degradation from heat and age. However, even with best practices, the general rule of thumb is that you lose roughly 20% of your battery’s capacity after about 1,000 charges. You can avoid excess degradation by not using your phone while it charges, charging it less often (select phones with super long battery life rather than super fast charging), and don’t play heavy games that heat up your phone for excessively long periods of time.

Active apps

Believe it or not, phone software can screw up your battery life in a lot of different ways. The most obvious way is during active use. Some apps simply use way more battery life than others and using those apps have a huge impact on your battery life over the course of an average day.

GPS apps, camera apps, and apps that require large amounts of data transfer use more battery than something like a launcher app or a calculator. Snapchat, for instance, uses GPS, your camera, and large amounts of data, which will impact battery life far more than a file browser app, for example.

Apps that use multiple pieces of hardware to function usually use more battery than ones that don't.

Mobile games also use more battery than most apps. All of them require the CPU and graphics processor to render graphics, control the game’s AI, and play the game itself. Plus, today’s mobile games often require a data connection and, of course, your phone’s display. Fun fact, Pokémon Go was the first mobile game capable of using your GPS, Bluetooth, camera, display, and data all at once. Its very existence doubled battery pack sales.

The more battery intensive apps and games you use, the worse your battery life is. This produces a bit of a problem for end users. You can use your phone however you want, but you kind of lose the ability to complain about it if you play Call of Duty: Mobile for two hours a day. That said, these issues are being mitigated over time as processors get faster and more energy-efficient. The only way to save battery life here is to simply not use those types of apps or upgrade to more modern chipsets.

Passive apps

Of course, all of the above applies only to apps you actively use. A wholly separate problem is all of the apps and services that run passively. The kinds of apps we’re talking about are podcast players, music apps, and many more. These apps run even while the phone display is off and have the potential to run for hours at a time.

It doesn’t take a rocket scientist to understand why these drain battery. Your phone is active even if it’s in your pocket. Plus, since most people stream music and podcasts, those apps are usually using data as well. Thankfully, these apps are heavily optimized so the battery drain is minimal in short bursts. However, some people listen to music for hours at a time and podcasts are usually 30-60 minutes apiece. The battery usage adds up over time.

Some other examples include torrent apps, weather apps if they’re set to update constantly, fitness tracker apps, and basically any app that you actively use without a screen on. They usually don’t make a huge dent in isolation, but if you use a lot of these all at once or for a very long time your battery life will take a hit.

Operating system and background tasks

Finally, we get to arguably the most important piece of software for battery life — the operating system itself. The OS can suck (or save) your battery life in a variety of ways since it controls everything on your device. Generally speaking, there is no one specific way the OS drains battery since everything it does affects battery to some extent. However, we’ve seen operating systems spiral out of control before, use way too much CPU, and burn power like no other, so it’s definitely possible.

Operating systems and battery life work the same was as CPU chipsets. Newer versions are generally more optimized, get work done quicker, and use less battery while doing it. Additionally, most operating systems introduce new features to control battery drain, control app usage, and optimize other things to draw less battery. The list of all of the various optimizations in Android is impossible to list here because of the sheer number of them.

The operating system is also built on a countless number of essential background tasks. Background tasks used to be a much greater battery hog until modern versions of Android optimized the process.

Background tasks drain battery in two main ways. The first is waking up your device in order to ping whatever the processes need to ping and the second is data usage. Your weather app updating in the background will ping its servers and wake up your phone, thus using battery. No single process uses a ton of battery most of the time. It’s the fact that your phone probably has dozens of these background processes running at once that causes problems.

Background tasks and processes aren't nearly the problem they once were thanks to Doze Mode and Adaptive Battery.

These are functionally impossible to deal with unless you have root access. Even then, root users can only do so much. The reason is that background tasks are the backbone of Android’s ability to multitask so most apps have the capacity to operate in the background even while not in use. You can’t really change how the OS works so the only thing you can really do is uninstall temperamental apps if they’re giving you a ton of problems.

Android itself deals with background tasks better than anything you can do anyway. Doze mode clusters background tasks to certain times and shuts them down otherwise. Additionally, Adaptive Battery shuts down background tasks of apps you don’t use very often. OEMs also add in additional battery saver modes so intense that it sometimes affects how apps even work. Android and OEMs leave this more or less out of your hands.

There are so many things that control or drain your battery that optimizing for them is nearly impossible. As a result, there are a lot of old wives tales and urban legends about battery drain, what causes it, and what prevents it.

You may hear some people simply tell you that the best way to not drain battery is to simply not use the phone. However, as we said earlier, lithium batteries lose charge and capacity over time anyway so it literally doesn’t matter what you do, your phone battery is going to discharge one way or the other.

The best way to save battery isn’t to adhere to an ancient list of outdated tricks that don’t work well enough if they even work at all. It’s also a bad idea to take advice that completely changes how you enjoy using your phone. The best way to save battery is to understand where your drain comes from and try to fix it at the source. Hopefully, with the help of this guide, you can do just that and score some outstanding battery life like I do. Good luck!

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