Leveraging Customized Heterogeneous Batteries to Alleviate Low Battery Experience for Mobile Users

Even with advances in single-cell batteries, mobile users still experience low battery anxiety. By analyzing 19,855 hours of user behavior, we propose MixMax, a heterogeneous battery system consisting of three complementary battery types tailored to minimizing low battery time. While the heterogeneous battery system offers an opportunity to simultaneously improve capacity and charging speed, one must face non-trivial challenges to design charge/discharge policies during runtime and determine the ratio of enclosed batteries. They are highly dependent on each other, which entails almost infinite candidates for the choice. MixMax simplifies this by reformulating the problem as an optimization problem, breaking it down into manageable sub-problems. However, MixMax still faces the challenge of catering to all users due to their diverse battery usage patterns. To address this, we introduce a customized MixMax that groups users based on their usage patterns and provides tailored battery solutions. In evaluating MixMax, we fabricate coin-cell batteries, develop a precise battery emulator using the fabricated batteries, and prototype MixMax on a real-world smartphone. Our evaluation shows that MixMax reduces low battery time by up to 24.6% without compromising capacity, volume, weight, or user behavior, and its customized version can further reduce it by up to 46.2%.