Remember the good old days when you had to keep your laptop plugged in until the moment that you boarded the plane so that you could work during the flight? It can be tough to go back there mentally in an era of widespread devices and laptops with all-day battery life. Part of the reason that we have such devices has been the rise of low-power-consumption processors; but focusing exclusively on the processor’s power efficiency will not tell you what battery life to expect from a device.
So what determines how long you can go without having to search for a power outlet? Some items you might have thought of, but others might be a surprise—or they might affect battery life in surprising ways. Here are some of the items with the largest impact on a device’s battery life.
Processors play a major part in determining battery life, but not always in intuitive ways. For example, many modern processors were designed with mobile workloads in mind, and thus they generally have a lower idle power draw than previous-generation processors.
Chip makers like Intel also coordinate processor development with mobile-operating-system designers like Google and Microsoft to optimize processors for mobile operating systems. This way, mobile and laptop operating systems can take advantage of more aspects of mobile processors to increase battery life.
Software designers also play a role here. Operating systems properly programmed to take full advantage of multiple processor cores or the 64-bit instruction set can go a long way toward conserving power while maximizing performance.
If you look at the battery settings on your mobile device, you can see how services and components on the device consume power. If you are like a lot of users, your display will usually be in the top three (if not number one) power consumers. This is because modern liquid-crystal displays (LCDs) are essentially lighting arrays with liquid-crystal shutters—pixels—that open and close in front of the light. Dimming your display can help reduce this power draw, but the longer you keep your screen on, the more it will drain your battery.
Radios: Phone, Wi-Fi, Bluetooth, GPS
Modern mobile devices can come with a huge array of radios. These handle everything from voice communication (phone), network communication (Wi-Fi and 4G), positioning and altitude (Global Positioning System [GPS]), and inter-device communication (Bluetooth and near-field communication [NFC]).
All of these radios use the most power when they are actively broadcasting, but they require power even when they are merely passively listening. Shutting down unnecessary radios when they are not in use can save power and help extend battery life. (On your next long flight, notice the impact of having all of your radios shut off in airplane mode.)
The data-transfer speed of your radios can also impact the battery life of your device or laptop. The 802.11ac standard is two to three times faster than the 802.11n standard, meaning that an 802.11ac radio only needs to broadcast one third to one half the time of an 802.11n radio, reducing the power it consumes.[i]
The type of storage that your laptop uses—solid-state drive (SSD) or hard-disk drive (HDD)—can impact its battery life. Though specifics vary, HDDs can use up to three times as much power as SSDs.[i]
Operating System and Settings
Operating systems that are optimized for power efficiency (particularly when done in conjunction with processors) can increase battery life. This includes everything from how the operating system handles read and write calls to storage and memory to the efficiency of the operating system’s encryption and decryption engine. Though there is little you can do to affect this, you can adjust operating-system settings (such as turning on power-saving mode on a device and adjusting settings there) to increase battery life.
Animated wallpapers can be a fun way to personalize mobile devices, but they can also impact battery life. An animated wallpaper represents an additional, persistent computational job running on your device every time your screen displays your home screen or desktop.
VPN connections are an integral part of many enterprise network-security policies, but they can impact the battery lives of mobile devices and laptops. This is because the encryption and decryption of network packets on the VPN can be computationally intense, increasing the load on the device’s processor.
Some apps can require more or inefficiently called reads or writes to memory and storage. Some apps might set a device’s display to a default brightness. And even if apps are optimized for power efficiency, many continue to run in the background on mobile devices once they are opened, even if they are not in active use. Several apps left running in the background can add up to a significant power draw on mobile devices and can sap battery life.
Modern lithium-ion and lithium-polymer batteries—the workhorse batteries for the vast majority of mobile devices and laptops—do better at holding a charge with age compared to previous battery types, such as nickel-cadmium batteries. But your battery will still hold less charge with time. And battery failure is not uniform—charge degradation can be less noticeable in batteries with more cells than in those with fewer. (For batteries with more cells, the failure of any given cell represents proportionally less of the battery being rendered useless than in batteries with fewer cells.)
This isn’t an exhaustive list of all the things that can affect battery life, but it should give you a better sense of how incomplete a pictured of batter life just focusing on the processor will give you when it comes time to purchase your next mobile device To get more information and to see some real-world comparisons between devices, read our white paper.
[i] Wi-Fi Alliance. “802.11ac: Wi-Fi for the next-generation of wireless connectivity.” October 2013. www.wi-fi.org/beacon/clint-w-brown/80211ac-wi-fi-for-the-next-generation-of-wireless-connectivity.