1.   http://www2.epa.gov/sites/production/files/2014-­‐01/documents/lithium_batteries_lca.pdf  2.   http://www.newark.com/pdfs/techarticles/tektronix/LIBMG.pdf  

 

myPower Final Report Tejas Shastry, Alexander Smith, Michael Geier

Scope: Smartphone users constantly face battery life issues. myPower aimed to solve this issue in a sustainable way by providing a portable battery for smartphones that charged from a user’s kinetic energy. The goals of this project were threefold: (1) develop a portable kinetic charger for smartphone users, (2) develop a smartphone app that tracked a user’s battery life usage and power generation, (3) analyze the carbon offset based on the production of the device and the generation of power from normal use. AMPY MOVE motion-charger: The AMPY MOVE is a portable kinetic battery for smartphones partially developed using the funding from the ISEN award. The 1800 mAh battery inside is charged in two ways (1) through the micro-USB port on the bottom of the device and (2) through the coupled inductors on either side of the device (Figure 1A). Each inductor comprises two copper coils wound in opposite directions such that the magnetic field of a magnet within the coil is always maximized in the appropriate direction. Each inductor produces a peak-to-peak voltage of 48.8 V (Figure 1B) and 33.7 mA (Figure 1C). For an iPhone 5C under normal use (15% active use and 85% standby use), an hour of running provides up to 1 hour of normal use or 5 hours of standby use battery life. AMPY+ smartphone app: The AMPY+ smartphone app is a standalone app for iPhone and Android, partially developed using the funding from the ISEN award. The app has three core features (1) battery life prediction, (2) power and fitness tracking, and (3) competition with friends. The battery life prediction utilizes an algorithm that measures the user’s smartphone usage over time and predicts battery life based on the day of the week, the time of the day, and the use within the last few hours (Figure 2A). The power and fitness tracking utilizes the sensors within the user’s phone to calculate the steps the user has taken that day and the calories they have burned (Figure 2B). Using the battery life prediction, the app then calculates the hours or minutes of battery life the user would have generated with the AMPY MOVE device based on their daily activity and daily smartphone use. The app also calculates the number of kilojoules of energy the user has expended. The user can then add their friends through email or Facebook to compete with them over generating the most joules (Figure 2C). Pilot test and sustainability effect: We piloted AMPY+ with over 1000 users and shipped AMPY MOVE to over 6000 users worldwide. We found that of our pilot users, smartphone battery usage varied throughout the week, with users experiencing less battery life the second half of the week (Figure 3). Using this usage profile and a life cycle analysis of the AMPY MOVE production using known CO2 equivalents of a lithium ion battery1 under normal cycle life,2 we found that the AMPY MOVE device offsets its carbon footprint within 85% of the battery’s life (Table 1). Based on our users’ average use, this will typically take 3 to 4 years. We found that users on average generated 11 hours of battery life per month, along with many other findings detailed in Figure 4. Summary: Using the funding provided by our ISEN grant, we were able to develop the AMPY MOVE motion charger and AMPY+ smartphone app. In doing so, we developed a way for active users to charge their smartphones from motion and partially offset the carbon footprint of doing so.

 

Figure 1. (A) Structure and features of AMPY MOVE motion charger. (B) Voltage and (C) Current waveforms of a single AMPY MOVE inductor under 4 Hz oscillation, equivalent to human running.

Figure 2. AMPY+ smartphone app for iPhone and Android featuring (A) battery life prediction, (b) power and fitness tracking, and (c) competition with friends.

(A)

(C) (B)

(A) (C) (B)

 

Figure 3. Measured total smartphone battery life for AMPY+ pilot users based on day of the week. Table 1. Life cycle analysis of AMPY MOVE product under normal use

Global Warming Potential

(kg CO2e / kWh) Primary Energy Usage

(Mj / kWh) kWh years Lithium Ion Battery 112 1780 AMPY Battery (5700 Wh) 0.6384 10.146 AMPY Inductors Copper Wiring 0.2119 2.6457 Magnets 1.325 16.45 Total 1.537 19.0957 Yearly wall offset 1.93 Total battery cycle life 2.28 Years to offset AMPY battery 2 Years to offset AMPY additions 1.4 Total years as a percent of cycle life 84%

 

Figure 4. Summary of pilot test results of AMPY+