Sunday, February 28, 2016

Tips to help you with your phone's battery life and myths debunked

One of the biggest complaints people have about their smartphone is that the battery doesn’t last long enough. For many people, just making it through the day can be a challenge, which is why you see so many “How to make your phone’s battery last longer!” articles in your friends’ Facebook feeds. But many of the claims in those articles are specious at best, and some of the tricks they suggest could actually shortenyour battery life. So which ones should you try?
Big battery suckers

Before we get into the specific changes—to settings or behavior—that you can make to extend your phone’s use time, we want to point out some activities that have a big impact on your battery. The following may seem obvious to you, but many people engage in these activities regularly.

One is streaming video. Watching a movie on, say, Netflix requires your phone’s screen to be on continuously (the biggest battery drain), your phone to maintain an active Internet connection (another notable drain), and the phone’s processor and graphics processor to decode the video and audio. For example, we watched Pee-wee’s Big Adventure on Netflix with the volume and screen brightness both set at 50 percent. On an iPhone 6s Plus, streaming over Wi-Fi for an hour consumed 5 percent of a full battery; LTE streaming used 11 percent. On a Moto X Pure, Wi-Fi used 11 percent of a full battery, and LTE used 13 percent.

Similarly, when you’re using a mapping app for long navigation sessions, your phone’s screen is on and the app forces the phone’s GPS circuitry to refresh at a more frequent rate than in normal usage. It’s also making heavier use of cellular and Wi-Fi connections in order to aid in pinpointing your location. These tasks all require quite a bit of energy.

If your battery is getting low, or if you need it to last longer on a particular day, avoid video streaming and GPS navigation unless you’re connected to a power source.

The easiest solutions

Anyone can make a few simple changes to their phone’s settings, or to their own behavior, that can have a significant effect on how much power a device uses. These tasks require little effort or technical knowledge.

Use the screen less—or at least turn brightness down

The component that uses the most energy on your smartphone, by a considerable margin, is the screen: The more you use it—for checking Facebook, streaming Netflix, texting with friends, whatever—the faster your battery drains. If you’re concerned about running your battery down too quickly, limit the amount of time you’re actively using the phone (that is, with the screen on). The more your phone sits in your pocket or bag, the longer its battery will last.

Of course, many of the things that you bought a smartphone to do require the screen. But a quick and easy change that can help extend its battery life without much fuss or annoyance is to shorten the delay until your phone automatically turns its screen off. This tweak reduces the amount of time the screen is on each day. For example, if you unlock your phone 25 times per day, and your screen-lock delay is three minutes, changing the screen-lock setting to one minute can cut the time your screen is on by up to 50 minutes. On an iPhone, go to “Settings” then “General” then “Auto-Lock”; on an Android phone, go to “Settings” then “Display” then “Sleep.” Alternatively, you can manually put the phone to sleep whenever you’re done using it.

When you are actively using the phone, you can extend the battery life by reducing screen brightness: In testing using the Geekbench utility’s battery-intensive routines for an hour, an iPhone 6s used 54 percent less battery—12 percent of a full charge versus 26 percent—with the screen brightness at minimum compared with maximum brightness. A Moto X Pure Edition Android phone used 30 percent less (21 percent of a full charge versus 30 percent).

Using a dim screen in bright environments is tough, however, so most phones offer an auto-brightness mode that automatically adjusts the screen’s brightness based on ambient light: In bright environments, the screen gets brighter, in dim environments, it gets dimmer. In a moderately well-lit office, our iPhone 6s test phone used only 16 percent of a full battery over an hour of the Geekbench stress test with auto-brightness on (with initial brightness set at 50 percent). With our Android test phone, a similar test resulted in the phone’s using 25 percent of a full charge. In other words, enabling auto-brightness will save most people a good amount of battery life compared with setting it to a bright level all the time, though not as much as if you kept the brightness down all the time; the advantage of auto-brightness is that the screen will remain easily readable in all environments.

Use an ad blocker

If you spend much of your smartphone-screen time on the Web, one of the easiest ways to make your battery last longer may surprise you: Install an ad blocker. Much of the debate around using this kind of software, which is designed mainly to prevent certain kinds of ads from loading while you’re browsing websites, focuses on revenue (for publishers) and annoyance (for readers). But ads, just like any other form of online content, use resources: Your phone must download the ad images and video and then display them (often running browser scripts too), and these tasks use energy.

We ran an automated Wi-Fi Web-browsing session in Safari on an iPhone 6s, cycling through a set list of websites for two hours with no ad blockers; then we ran the same test with the 1Blocker ad blocker installed. Without the ad blocker, the test used 18 percent of the phone’s battery, but with the ad blocker, it used only 9 percent—so viewing ads doubled the impact of Web browsing on the phone’s battery! We ran a similar test on a 2015 Moto X Pure using the Ghostery Privacy Browser and got results that were even more dramatic: With no ad blocker, a two-hour browsing session in Chrome used 22 percent of the phone’s battery, whereas the Ghostery ad-blocking browser (which uses the same browser engine as Chrome) consumed only 8 percent.

Switch from push to fetch email if you have many accounts or get lots of email

A feature called push automatically delivers new email, new or revised calendar events, and updates to your contacts list (such as from a Gmail or iCloud account) to your smartphone whenever such changes occur on a central server. Although push is convenient, the feature can use a goodly amount of power, as it requires your phone to always be listening for new communications from your account provider. Most phones let you configure them to use “fetch” instead, where the phone polls a server on a schedule—say, every 30 minutes—or only when you manually tell the phone to do so.

If you have a single email account and you don’t receive much email, you won’t see a real difference in battery usage between push and fetch. But the more accounts you have on your phone, and the more messages and events each of those accounts receives, the more energy your phone will use, as it has to communicate with those account servers continually. For example, to compare the effect of push versus fetch on the same email load, we tested an iPhone 6s Plus configured with three email accounts, receiving a total of 20 to 30 messages per hour. Over 24 hours with push enabled, Mail was active in the background for about 18 minutes. When we switched to a 30-minute fetch schedule, the same phone, handling roughly the same amount of email, was active in the background for only 4 minutes over 24 hours. It’s difficult to determine conclusively how much of Mail’s energy use is specifically attributable to communication with mail servers, but in these tests, having push active over the course of a day with this particular email load caused Mail to account for 5 to 10 percent more of the phone’s total battery use.

The manual setting will save the most battery life, but you likely won’t see a huge benefit over fetch, and you’ll lose the convenience of being notified of new mail and events on a regular schedule.

If you switch from push to fetch or manual, and you don’t notice an improvement in battery life after a few days of use, you might want to switch back to push for the convenience it offers. Alternatively, you can enable push for only those email accounts on which you really do need to see messages immediately, using fetch or manual for the others.

Store music locally

More and more people are using streaming services such as Apple Music, Pandora, and Spotify to get their tunes. However, streaming requires your phone to maintain an active wireless connection—Wi-Fi or cellular—to the service you’re using to stream music. This active connection consumes a significant amount of power in comparison with playing that same music if it were stored on your phone.

For example, in our testing, playing locally stored music over Bluetooth headphones and speakers for two hours used about 5 percent of an iPhone 6s Plus’s battery. Streaming that same music over a strong Wi-Fi connection used 10 percent of the phone’s battery—twice as much.

Some services, including the paid versions of Apple Music and Spotify, let you download individual playlists to your phone. (In Apple Music, for example, you just tap the cloud icon at the top of a playlist.) Once you’ve downloaded a playlist, its music plays from the phone’s storage instead of streaming over the Internet. (To get the maximum battery savings, you should perform these downloads while your phone is on Wi-Fi and plugged into power.)

Avoid extreme temperatures

While battery technology continues to improve, smartphone batteries remain sensitive to temperature—they work much better when you use them in moderate temperatures. Apple notes, in its publication on maximizing battery performance, that you’ll get the best battery life when you use the phone in temperatures of 62° to 72° Fahrenheit. In cold temperatures, you’ll see much shorter battery life, though the battery will regain its normal use time when the phone warms up. Excessive heat, on the other hand, can permanently shorten your phone’s use time—you shouldn’t use or store your phone in extremely hot environments (this includes leaving your phone in the car on sweltering summer days).

Use airplane mode or low-power mode (if you must)

Both iOS and Android phones include an airplane mode that disables all wireless circuitry, including Wi-Fi, cellular, Bluetooth, and NFC. (On some models of phones or older operating system versions, it also disables GPS.) Though the mode was originally designed to prevent phones from (theoretically) interfering with airline communications, it also reduces battery usage—all that wireless circuitry requires power. Indeed, in our testing on Android and iPhone smartphones, enabling airplane mode resulted in the battery level dropping by just a few percent over four hours during normal use (or as normal as use can be when the device is in airplane mode, as we note below). Contrast that to nearly 10 percent over four hours during the same type of use with airplane mode disabled.

Similarly, both iPhones running iOS 9 and later and Android phones running Android 6.0 Marshmallow include a low-power mode (sometimes called battery-saver mode) that significantly reduces the phone’s power usage by disabling power-hogging features. For example, on an iPhone, enabling low-power mode disables email fetch, the Hey Siri feature, background application usage, automatic downloads of app updates and other data, Wi-Fi scanning, and some visual effects. Both platforms can automatically switch to low-power mode when the battery level dips below a certain threshold (to squeeze an extra hour or so out of your phone when its battery gets low), or you can make the switch manually at any time. In our tests, both iPhones and Android smartphones used significantly less battery power with battery-saver mode enabled—as much as 54 percent, depending on the phone we used.

While both airplane mode and low-power mode conserve battery life, they do so at a heavy price. With airplane mode you lose the ability to communicate with another device, be it a wireless keyboard or another phone, as well as the ability to access Internet services. If you forget to disable this mode, you might miss calls and text messages or be unreachable for loved ones. Low-power mode similarly disables many useful features, including background processes’ use of wireless communications. This limitation makes a smartphone less, well, smart. We recommend using these modes only when you must, rather than as regular battery-saving methods.

Airplane mode is most useful when you’re in areas with bad reception and your phone starts consuming a lot of energy searching for signals—enabling airplane mode prevents your phone from expending that energy. Low-power mode is a better alternative when your phone’s battery is on its last legs and you just need to make it to the next charge, or when you know you’ll be away from power for a prolonged period and you want to stretch the phone’s full charge as long as possible.

The next steps

The easy procedures above will produce good results for many people. But if you use your phone a lot over the course of the day, if you frequently use location-related apps and services, or if you regularly find yourself in areas with bad cellular or Wi-Fi coverage, you can expend a bit more effort to improve battery life.

Disable cellular or Wi-Fi when the signal is bad

You may have noticed that when you’re in a place without good Wi-Fi or cellular coverage (say, when you’re camping in a remote area), your phone’s battery seems to drain much more quickly. Modern smartphones are designed to use the minimum amount of power to get the best connection, so when you’re in a spot with good coverage, such as in an urban area, power usage is much lower—sometimes by factors of ten—than when you’re in a rural area with poor coverage, or where you have no signal and the phone is constantly searching for one.

You can’t improve the signals in areas with sketchy or no coverage (other than by upgrading your home Wi-Fi router to get a better signal there, perhaps), but you can conserve battery life by disabling the phone’s wireless circuitry. However, rather than using airplane mode (described above), you can disable just the wireless feature that’s using lots of energy.

For example, if you have terrible wireless-carrier coverage in your office, but Wi-Fi is great, disabling cellular connectivity will keep the phone from wasting energy trying to get a cellular connection while still letting you connect to the Internet over Wi-Fi; conversely, if your phone struggles to stay connected to your home Wi-Fi network when you’re in the backyard, you should disable Wi-Fi and use cellular data instead.3

If you’re in a location with solid Wi-Fi but poor cellular coverage, note that some smartphones on some carrier networks can use Wi-Fi calling, which routes calls over a Wi-Fi network. Some cellular carriers also offer “micro-cells,” which plug into your Internet connection to provide a strong, local cellular signal over licensed frequencies for that carrier in your area.

Consult your phone’s battery-usage screen to find the biggest offenders

Both phone platforms provide a simple way for you to see which apps are using a lot of battery power. For example, on an iPhone running iOS 9, go to “Settings” then “Battery,” and scroll down to “Battery Usage” to see a list of the apps using the most battery power, sorted by the amount consumed. By default, the list shows battery use over the past 24 hours, but you can tap “Last 7 Days” to see data from the past week, which is often more useful; be sure to tap the little clock button to reveal information about how much of your battery life each app is consuming when you’re actively using the app (“screen”) versus when you’re not (“backg…” or “background”).

On Android, you can see a similar list by going to “Settings” then “Battery”; here, too, you’ll see a sorted list of the items that are using your battery power. “Screen” is just that, your backlit display, while “Google Play Services” is a catch-all label for many apps’ background actions. Tap on an app, and you’ll see detailed statistics. You’ll find the most useful information in the “CPU total” and “CPU foreground” timers. The “foreground” figure refers to how much time you had the app open; subtract “foreground” from “total,” and you’ll know how much time the app has been busy in the background.

Using this list, you can quickly see which apps are the biggest battery-use offenders. You’ll likely find that the apps with the highest battery usage also have the longest on-screen time—in other words, they’re using a lot of battery because the screen is on most of the time you’re actively using them. You won’t be able to do much about those apps other than to use them less.

Other apps, however, consume a seemingly disproportionate amount of power when you’re not actively using them, and the information on background time is especially useful here: Be on the lookout for apps that are active for extended periods in the background and are using a lot of battery power, because these apps are sucking battery juice even when you aren’t actively using them. Examples might include an email app that spends lots of time checking for new messages even when your phone is asleep, an RSS reader that updates articles in the background, or a fitness app that constantly monitors your location. (The Facebook app for iPhone was a notorious battery killer, using lots of energy in the background, though a recent update claims to have fixed the issue; the Android version recently came under criticism for the same problem.)

If you find such apps, you’ll need to decide whether this background activity is important to you. If you can do without it, you can likely disable it. For example, on an iPhone, you can go to “Settings” then “General” then “Background App Refresh” to choose, for individual apps, whether each one can refresh its content in the background; you can go to “Settings” then “Privacy” then “Location Services” to determine whether an app can track your location in the background. On Android, go to “Settings” then “Data usage,” select an app, and choose “Restrict background data” for background data usage; to disable location tracking, go to “Settings” then “Apps,” choose an app, select “Permissions,” and then tap to disable location permission. Disable these settings, and the app’s background use will likely go down considerably, if not completely.

Some apps are regularly active in the background, but you may be willing to put up with that because you find what they do useful, or because they don’t draw a huge amount of battery power. For example, on one of our test iPhones, the Moment app, which tracks location and activity throughout the day, used power in the background for nearly 94 hours over 7 days, claiming about 5 percent of overall battery use during that period. But if you value Moment’s tracking and analysis, you might consider that amount of battery usage to be acceptable.

If you disable background activity for a particular app, but it persists in using a large amount of power in the background, the app may have a bug.

Disable GPS or location services—but only for power-hungry apps or apps you don’t need

Your phone’s GPS hardware, which it uses (along with Wi-Fi and other technologies) to determine your geographic location for mapping, run/bike-tracking, and other location-based features, consumes a lot of battery power. However, well-managed location services consume only a moderate amount of battery power.

For example, using the Maps app on an iPhone or Android phone for GPS directions for a short trip will consume minimal battery life, as these apps are designed to minimize GPS use; having the screen on during that navigation will consume significantly more. (This is, in part, why long navigation sessions use so much of your battery—you likely keep the screen on for the duration, and the screen draws a lot of power.) Similarly, step counters and activity-tracking apps that aren’t constantly monitoring your location don’t require much power while tracking in the background.

However, a run-tracking program that’s monitoring your precise location for the duration of an hour-long run will affect your battery level. You can take advantage of the previous tip (going through the battery-usage screen) to find big offenders: If a location-based app is using a lot of battery power, especially in the background, chances are good that the app is using GPS, Wi-Fi, and the phone’s sensors frequently. Depending on how much you value that app’s features, you can choose to let it continue to do its thing, or you can disable location features for it (either via your phone’s location-services settings or through the settings in the app itself).

Note that on an iPhone, some apps let you choose whether to enable location services for each app all the time, or only when you’re actually using the app—an option we wish more apps would provide. If you choose “While Using the App” (under “Settings” then “Privacy” then “Location Services” then the app’s name), the app will still be able to determine your location while you’re actively using the app—in other words, when it’s on the screen—but not when it’s in the background.

Android similarly allows you to change an app’s permission to get your location (go to “Settings” then “Apps,” choose an app, and tap “Permissions”), but your only options are to allow or prevent that access. You can, however, set a systemwide location limit: Go to “Settings” then “Location,” and choose between “High accuracy” mode, which uses GPS, Wi-Fi, Bluetooth, and cellular networks to determine your location, or “Battery saving” mode, which disables GPS to save energy at the cost of accuracy.

Disable unnecessary push notifications

In addition to push email, which automatically notifies you of new email messages as they arrive, smartphones support push notifications, which allow apps to provide new information, sound alarms, display reminders, and more, instantly. Push notifications can be very convenient—they’re part of what makes a smartphone great—but every notification uses a bit of energy, as it requires your phone to wake up for a few seconds, including turning on the screen, to show you a message and give you a chance to act on it. If you get a lot of notifications, that energy use can add up 4.

Determining exactly how much energy notifications use is difficult. Receiving a few dozen notifications over the course of an hour didn’t noticeably affect battery usage—but both Apple and Google recommend disabling notifications as a way to conserve battery power. If a particular app or service (say, Twitter or your email client) is constantly producing notifications, consider disabling notifications for that app. On an iPhone, go to “Settings” then “Notifications,” tap the app name, and disable “Allow Notifications” (or switch to a less-intrusive form of notifications, such as a Badge App Icon). On Android, go to “Settings” then “Apps,” tap the app, choose “Notifications,” and then toggle the switch for “Block all” to prevent that app from bothering you.

As a bonus, fewer push notifications means fewer interruptions in your day and less time spent using your phone (which, of course, also helps your battery last longer).

If you get a lot of notifications but have reasons (or just a predilection) to keep them coming, consider disabling notification vibrations instead. Every time your phone vibrates, it uses energy to move a little motor in the phone; over dozens or hundreds of notifications, that power drain adds up. On an iPhone, you can disable all vibrations by going to “Settings” then “General” then “Accessibility” then “Vibration.” Alternatively, you can go to “Settings” then “Sounds” and tap individual items under “Sounds and Vibration Patterns” to disable vibrations for each. On an Android phone, you can disable the tiny vibrations that happen every time you touch the screen (if they’re enabled on your phone) by going to “Settings” then “Sound & Notification” then “Other Sounds” and disabling “Vibrate on touch.” On most recent Android phones, you can temporarily turn off vibrations (and sounds) by enabling “Priority only” or “Do not disturb” mode, either from your Quick Launch settings (pulling down from the top-right side of the screen) or by clicking the volume rocker all the way down and then clicking down one more time.

For iPhone: Use Bluetooth instead of AirPlay to listen wirelessly

AirPlay is Apple’s alternative to Bluetooth for streaming music wirelessly from your phone to speakers. AirPlay claims better sound quality and longer range, thanks to its use of a higher-quality audio format and your existing Wi-Fi network, but AirPlay uses quite a bit more of your battery than Bluetooth.

We tested audio streaming via AirPlay and Bluetooth from an iPhone 6s Plus, first using locally stored music and then using tunes streamed from Apple’s Apple Music service. When playing locally stored music, AirPlay used 13 percent of the phone’s battery over two hours, while Bluetooth used only 5 percent.

Interestingly, when streaming the same music, AirPlay used barely more juice, 14 percent, because the phone was using the same Wi-Fi connection for both tasks; Bluetooth’s battery usage, however, jumped to 10 percent, because the phone had to use Wi-Fi—to stream the data from Apple Music—whereas it didn’t before. In other words, Bluetooth uses less of your battery than AirPlay, but you’ll see the biggest battery savings if you store your favorite music on your phone, as noted above, rather than stream it from the cloud.

Battery-saving myths

You’ve probably seen lists of things you should supposedly do to extend your phone’s use time. Some of them may be described above. But other tricks don’t really help your phone use less energy—in fact, some may cause your phone to use battery energy more quickly. Here are some suggestions that you may hear about but (with a few noted exceptions) you shouldn’t bother doing.

Myth: Turn off Bluetooth

Many people recommend disabling Bluetooth on your phone to get better battery life. But Bluetooth was designed from the start to minimize battery usage, and it has only gotten better over time. In our testing, having Bluetooth on but not actively connected to a device used a negligible amount of battery power over several hours. Even when connected to a Bluetooth LE (Low Energy) device that regularly communicates with your phone, such as a recently made fitness tracker, Bluetooth uses very little of your battery. Where Bluetooth does have a noticeable impact on battery life is when you’re actively using the Bluetooth connection, such as when you’re streaming audio to a Bluetooth speaker or headphones. The lesson here is simple: If your battery is running low, you shouldn’t stream audio over Bluetooth. Use wired headphones, if you have them.

Myth: Turn off Wi-Fi

A similarly common suggestion for extending battery life is to disable Wi-Fi. However, if you’re in range of a strong Wi-Fi signal, your phone uses less energy to connect to the Internet with a Wi-Fi connection than a cellular one. In addition, if you regularly use apps that rely on your location, having Wi-Fi enabled helps your phone determine its location without relying solely on power-hungry GPS features, so it actually helps your phone’s battery last longer.

Unless you’re at the edges of a Wi-Fi network, where your phone is struggling to get a solid connection (see Disable cellular or Wi-Fi when the signal is bad, above), and you have a good cellular-data connection—in other words, your phone is keeping both Wi-Fi and cellular active, and switching between the two—you’re usually better off keeping Wi-Fi enabled.

Myth: Close (quit) unused apps

There’s a good chance you’ve seen this “tip” for extending battery life: Close (or force-quit, as it’s commonly called) apps that you aren’t currently using. (On Android, you press the task-switching button and swipe an app to the side to quit it; on an iPhone, you double-press the home button and then swipe an app’s screen upward.) The theory here is that apps running in the background are using your phone’s processor, memory, and other components, so quitting them will use less energy.

Although that may sometimes be true on a computer, smartphones are designed differently: Once an app is no longer in the foreground—meaning you aren’t actively using it—most or all of its processes are frozen. While an app may still be loaded in RAM (temporary memory), the app is unlikely to be doing stuff in the background to drain your battery. Your phone’s operating system also automatically closes apps in the background when it needs RAM for other tasks. Finally, quitting apps can actually have drawbacks: When you force-quit an app, that may purge all of its code from your phone’s RAM, which means that the next time you open the app, the phone has to reload all of that code—which, of course, requires energy.

For the most part, you can just use your phone and its apps, without having to worry about force-quitting anything or installing an app that claims to “manage” your memory. Of particular concern are apps that you’ve specifically given permission to do things in the background, such as apps that monitor your location, and apps that refresh their content in the background. You likely want them to perform those tasks—force-quitting the apps will prevent them from doing the very things you gave them permission to do.

A better approach is to use your phone’s battery-usage screen, as explained above, to find the biggest battery-usage offenders. If an app is listed there as consuming a huge amount of battery power, and it isn’t an app you’ve been actively using or one that you’ve given permission to do a lot of things in the background, the app might have a bug that’s causing it to suck up battery power. In that case, force-quitting it is a safe approach. (You can then wait for an update to the app that, with any luck, fixes the bug.) If, as is more likely, an app is using a lot of energy because of allowed background or location activity, you’ll need to decide whether you want to disable background refresh or location services, respectively, for that app.

Myth: Use a battery-saving utility or task manager on Android

Along the lines of the previous myth, many apps in Google’s Play Store for Android claim to improve your phone’s performance by serving as an always-running “memory manager” or “task killer.” As noted above, manually closing applications is a bad idea—Android can properly keep apps and processes suspended, using little to no resources, just fine on its own. What’s more, Android automatically kills older processes, or big memory hogs, as performance starts to lag. Restarting applications repeatedly will probably cost you more battery life than leaving them alone, and any automatic task manager will itself be demanding power constantly from your phone.

Myth: Disable location services completely

As we mention above, many apps that use your location do so only intermittently—with the exception of a few bad apples, or apps that really do require constant location tracking, most apps are well behaved in this respect. Even using the Maps app for short navigation sessions doesn’t consume more than a few percents’ worth of your battery’s capacity—and as we noted, having the phone’s screen continually on is a big part of why navigation draws a lot of juice.

As a result, we don’t recommend disabling all of your phone’s location-based features just to extend your battery life. In doing so, you’re unlikely to see a big jump in use time, but you may end up turning off useful features that you’ll miss having available. Instead, follow our tips above to check if any of the apps consuming the most battery life also track your location. If so, and if you don’t need that location tracking, consider disabling the function just for those apps.

Myth: Always choose Wi-Fi over cellular

Many people, and even smartphone vendors such as Apple, claim that using Wi-Fi for wireless data consumes less battery than using a cellular signal, so you should use Wi-Fi whenever you can. However, our testing found that this isn’t always the case. For example, when we tested in a location where both Wi-Fi and LTE signals were strong, on an iPhone 6s Plus an hour of browsing over Wi-Fi used roughly the same amount of battery power as an hour using LTE; on a Moto X Pure Android phone, LTE used only 2 to 3 percent more of a full charge than Wi-Fi. In other words, as long as you have a good signal, you probably won’t see a huge difference between Wi-Fi and cellular data, and switching between the two is likely not worth the hassle.

Where you will see differences is in areas where LTE coverage is poor. As we explain above, your phone uses significantly more power when trying to find and connect to a weak signal. So if you’re in a location where the Wi-Fi signal is bad, but you have a good cellular signal—so your phone is regularly switching between the two—disabling Wi-Fi and forcing your phone to use just cellular data will likely conserve battery power. Conversely, if your phone is struggling to get a good cellular signal, try finding an accessible Wi-Fi network (at a coffee shop or restaurant, for example) to use instead.

You’ll see the biggest impact of using cellular data when your phone has to switch between cellular towers in a continual search for a good signal. We found that after an hour of Web surfing, an Android phone had used roughly 4 percent of a full battery more when we were driving in a car than when we were stationary with a strong LTE signal; an iPhone used 8 percent more of a full charge. (The difference will vary by phone, carrier, and locations, of course.)

That said, in situations where you’re roaming on cellular data, you likely won’t have the option to use Wi-Fi (unless, for example, you’re on a train that offers Wi-Fi), so your only real option there is not to use cellular data at all—which might be inconvenient but will conserve a lot of battery power.

Myth: Disable Hey Siri or Ok Google

Both iPhones and Android phones include a hands-free feature for accessing their respective virtual assistants. With this feature enabled, you don’t have to press or hold a button to activate Siri or Ok Google, respectively—you just say, for example, “Hey Siri” and then speak your request or command. Although this feature is convenient, it requires your phone to constantly listen for that special phrase, which uses some power.

However, contrary to tips you might see online, if you have a phone that supports this feature, disabling it won’t conserve much battery life. In our testing with an iPhone 6s Plus and a Nexus 6P, we saw a negligible difference in battery usage between having the always-on virtual assistant enabled or disabled over a two-hour period.

There’s a good reason for this: On the iPhone side, only the iPhone 6s and 6s Plus allow you to enable always-on Hey Siri while the device is on battery power, because these models use newer components (specifically, Apple’s M9 motion coprocessor) that allow Hey Siri to function on minimal power; older iPhones can use Hey Siri only when charging. Similarly, only some Android phones with certain energy-efficient components provide the option for always-on Ok Google; on other models, Ok Google works only when the the screen is on, when you’re already using the phone.

Actually using Siri or Ok Google uses some energy, so if your phone’s battery is getting low, you should probably stop asking the phone question after question during your commute. But just having the feature enabled isn’t worth worrying about—and the feature can be quite convenient.

Myth: Calibrate your battery to extend its life

For many years, devices that used rechargeable batteries required “conditioning” or “calibrating,” a procedure that prevented the battery from forgetting how much capacity it actually had if you didn’t fully drain the battery between charges (a phenomenon called the memory effect). Today’s smartphone batteries no longer suffer from this issue.

However, every battery does gradually lose capacity over time as you use and recharge it, and the phone’s software isn’t always good at accounting for this capacity change. If you periodically (once every couple months) charge the phone fully and then use it until it dies, your phone’s software will determine the battery’s current capacity and thus allow the phone to better estimate how long it will last on a charge. The battery won’t last any longer as a result, but the phone’s battery meter will be more accurate. If you find that your phone claims it has 80 percent of a charge left but dies a few hours later, try this procedure.

Myth: Use only the charger that came with your phone

A common warning around the Internet is that you should use only the charger that came with your phone. This idea isn’t so much about extending your battery life on a daily basis but rather a warning that using a different charger could damage your phone’s battery—either by being poorly made or by supplying too much power.

Several warnings are woven into this claim. The first is that only your phone’s own charger is safe. In reality, the phone itself contains all the circuitry responsible for charging its battery. The AC adapter (as it’s more accurately known) simply converts the AC current from a wall outlet into low-voltage, low-amperage DC current that it provides via a USB port. This is why you can charge your phone using the USB port on a computer, a USB battery pack, or a charger in your car—the phone is designed to charge from a variety of power sources that can produce a wide range of current.

For example, the charger that ships with an iPhone supplies about 1 amp of current, but the phone can also charge from a 0.5-A USB port on a computer, or even from the 2.4-A chargers that are becoming increasingly common. And some flagship Android phones come equipped with Qualcomm’s Quick Charge technology, which allows faster charging—with a compatible charger—by bumping the voltage rather than the current.

Similarly, some people worry that using a higher-current charger with your smartphone—say, by using Apple’s iPad charger with an iPhone, which charges the phone much faster—will damage the phone’s battery. You do have some theoretical risk here, as charging a battery with too much current can shorten the battery’s life cycle (how long it will maintain good capacity) over long periods.

However, current smartphones are designed to work with a wide range of charging currents—Apple specifically lists all iPhones as being compatible with the company’s iPad chargers—and the phones themselves limit the maximum current used to charge the battery. For example, if you use a recent iPhone with a charger that can provide up to 2.4 A, the phone draws a maximum of 2.1 A when charging. And even if using a higher-current charger on a daily basis does affect the battery’s life cycle, you likely won’t see a difference unless you keep the phone for longer than a couple of years—at which point you’ll be seeing shorter battery life anyway (just possibly not as short) due to age of the battery.

Finally, you may read warnings that a cheap third-party charger could damage your phone. There’s some truth in this claim: Many chargers you can buy, especially budget models you’ll find online or at your local shopping-mall kiosk, are poorly made or constructed with low-quality components. Some of these chargers are counterfeit, sold as believable-looking versions of phone makers’ own chargers. (Engineer Ken Shirriff has a great examination of what’s inside Apple’s iPhone charger in comparison with budget models.) A poorly made charger can not only damage your phone but could also hurt you by exposing you to dangerous currents. So if you’re replacing your phone’s AC adapter or buying an extra, stick with a reputable vendor that sells UL-listed models.

All of this is to say that as long as you’re using a well-made charger, it’s okay to use one that charges your phone more quickly than the charger it came with, or one that can charge even faster than your phone allows.

If you still need more juice: Battery packs

If, after following these tips, you find that your phone still can’t survive through the day, the battery may be defective; you should take your iPhone to an Apple Store, or contact your Android phone’s vendor, to rule that possibility out. (Some extended warranties for smartphones, including AppleCare+, cover replacing a battery that has declined below a certain amount within the warranty period.)

If the battery is fine, and the phone is less than two or three years old—so you don’t plan on buying a new one with better battery life soon—you might consider purchasing an external battery. These accessories, which can take the form of a bulky case with a built-in battery, or a separate battery that connects to your phone with a cable, provide the power you need to last an additional few hours at the end of the day, or even to fully charge your phone’s battery.

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