We all should read more books.
However, our hands are usually occupied by smartphones and tablets. A brilliant solution to this problem is an audiobook app. We tested the battery life of several audiobook apps, on both Android and iOS platforms. As this article is not yet available in audio format, please read on.
Audiobook applications are really popular these days. Commuting becomes a pleasant experience, when you can lean back on your seat, close your eyes and listen to Fifty Shades Darker. And just when the book gets really interesting, your battery runs out… Not cool.
We wanted to see how much the audiobook apps consume power, both in WiFi and in cellular network. In addition, we investigated the effect of different audio interfaces. The tested apps were:
- Audio Books
Our test devices were Samsung S7 Galaxy and Apple iPhone 6s. All background syncing activities were disabled during tests, to prevent any “noise” to our measurements. During WiFi tests, the device was idling on cellular network but mobile data was disabled. During cellular network tests, WiFi was disabled. The measurement time was 10 minutes (after 1 minute wait period).
First testing round was done in WiFi network and with wired headset. The average power consumption of the apps were 160mW in iPhone and 270mW (= +70%) in Samsung. This was not a big surprise; Apple has had a superior power efficiency for a long time. This can be seen in our other measurements as well.
Second test round was done in different cellular networks, which revealed the power consumption differences between apps. The differences are mostly a result of how the apps handle the loading of the book. Typically the most power efficient way to load data is to load it all to device. This minimizes the network timeout periods. The basic idea of these timeouts is to leave the data connection open for a certain period of time (configured by network/operator), thus making the device able to continue data transfer quickly if needed. This improves the user experience by lowering latency.
There were two apps, that loaded the whole book into the device. You can guess which they were, by looking at the graph above. Audible and LibrVox were clearly the best apps from power consumption perspective.
It was interesting to notice, that in many cases 4G connection was more power efficient than 3G connection, even though 4G is typically a bit more power hungry. This is due to a new power saving feature implemented into 4G, called Discontinuous Transmit/Reception (DTX/DRX). It enables the device to keep the data connection open during the network timeout period, but instead of being active all the time, the device can go to sleep in between checks for data transfer activity.
The comparison between different audio interfaces gave expected results.
Wired headset is most power efficient choice. Using the internal speaker at 50% level did not increase the power consumption a lot in most of the cases, but it should be noted that increasing the volume level has a huge effect on power (especially on devices with stereo speakers).
Especially in iPhone, there were clearly differences between apps when using Bluetooth headphones. The power consumption is affected if high quality codecs are being used. It is questionable, if they are needed when listening to audiobooks.
From battery life perspective, none of the audiobook apps are draining your battery too much. The effect on your battery capacity should be 2%-4% / hour, taking the audio interface and network choices into account.
For the best battery life experience, you should read a real book. The second best choice is the combination of an iPhone, wired headset and either Audible or LibrVox as the audiobook app.