A definitive guide to everything that affects smartphone battery life - Android

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

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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

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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.

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