The wearable electronics market is experiencing a significant boom now. Although Gartner reported that wearable fitness trackers are expected to fall from 70 million units in 2014 to 68.1 million units in 2015 due to the introduction of smartwatches, it is still popular amongst both fitness enthusiasts and mainstream users.

However, battery life has always been a major concern in wearable devices. As the features increase, the battery life decreases notably. The geographical positioning system (GPS) module also consumes a lot of power. Let us understand this problem better by looking at the electronic components that go into four major models of wearable fitness bands available in the market today, and how their specifications and features influence the battery performance. The devices we delve into are Garmin vívofit, Microsoft Band, FitBit Flex and Samsung Gear Fit.

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Processors at the heart of these devices
The signal processors used in these devices are ultra-low-power, high-performance chips with small form factors, suitable for wearable electronics applications. From the comparison in Table 1, we can conclude that the central processing unit (CPU) clock frequency of the processor affects the battery life inversely (except in the case of Microsoft Band, which can be explained by the number of features it offers). As the clock frequency increases, the processing speed of the CPU and hence the performance of the device increases, but the battery drains faster.

Effect of product features on battery life
Garmin vívofit offers the greatest battery life amongst these products, with the limitation that it offers only pedometer, temperature sensor and time display functions. Moreover, the two batteries cannot be recharged and have to be replaced by the user every time they are used up.

FitBit Flex uses a rechargeable battery that can run for five days on a single charge. Flex is capable of counting the number of steps taken, including stair climbing, using its pedometer and altimeter functions. It also has vibration alert for goal achievements, idleness reminder, etc.

Samsung Gear Fit has an accelerometer, gyroscope, digital motion sensor, continuous time display, and on-screen notification for call, text or other app notifications. Although it does not have an inbuilt GPS feature, it makes use of the phone’s GPS to track motion. The battery lasts for five days on typical usage.

The most number of sensors are integrated into Microsoft Band – accelerometer, optical heart rate sensor, gyrometer, GPS module, ambient light sensor, ultraviolet (UV) sensor, skin temperature sensor, capacitive sensor and galvanic skin response. It also displays time and phone notifications just like the Samsung Gear Fit. But, with these features, the user has to compromise on battery life. With all features enabled, it takes less than 48 hours for the battery to get completely exhausted.

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