Reliability Analysis of Low-cost Power Banks

Abstract

Portable charger is becoming a trend to the electronic device users, especially to consumers with high demands in the energy density, power density, long cycle life, and long shelf life of the battery. More low-cost portable chargers can be found in the market as the elasticity of demand for some consumers are high, which price will significantly affect their purchases. Therefore, the reliability of cheap portable chargers remains a great issue to discuss. In this project, the 5000mAh Xiaomi Power Bank is chosen as the target product to study the reliability of low-cost portable chargers. First of all, introduction of the concept of Lithiumion battery and some safety hazards will be covered. In addition, theories will be studied such as the reliability and mean time to failure, and the Highly Accelerated Life Test for providing solid information as the methodology. Apart from that, the target product will be introduced in detail in terms of its design and features. Moving to the experiments, four types of tests are conducted including the High-low Temperature Test, the Temperature and Humidity Test, the Highly Accelerated Stress Test, and the Thermal Shock Test in order to examine the reliability of the target product in a comprehensive approach. From the experiment results, it is found that the power bank will wear-out when the temperature is reached 120°C. From -20°C to -70°C, the power bank cannot operate temporarily until the cold temperature was compensated. According to the temperature and humidity test, it is found that the battery was swollen seriously with a significantly lowered output current. when the temperature reaches 85°C and the humidity percentage is 85%, however, the battery is still operative even the test duration is 400 hours. After conducting the Highly Accelerated Stress Test, serious damages to the battery and its electronic component is resulted, which the plastic on the surface was broken after. Analysis of the results will be further discussed in detail in the following sections. As considered the lowered effects of the result on the battery by the aluminum case, a disassembly method is carried out in other to eliminate those unfavorable factors. Furthermore, suggestions for future works on studying the reliability of low-cost power bank will be provided for the benefits of scientific researchers.