Dynamics and characteristics of thin film batteries cycled over capacitive load

Piezoelectric actuation has potential advantages in autonomous microsystems due to relatively high efficiency and low voltage requirements when deposited as a thin-film. However, the power available to autonomous microsystems may have many restrictions due to electrical loading, weight, and size requirements. Modeling of the power sources and loads can be beneficial for design and implementation; however, understanding the various associated phenomena is important for a valid model. This work examines mid-frequency cycled capacitive loading of thin film batteries to simulate application to autonomous micro-robots. Commercial 50μAh LiCoO2/Lipon thin film batteries were cycled over a frequency range between 100Hz-10kHz and at two levels of capacitance (1, 10nF). Detailed data was acquired of the dynamics of the battery and capacitor voltages during switching. The significance of understanding losses from switching and leakage at the micro scale is clearly shown. The impact of similarity in timescales for various dynamics is discussed. Additionally, indications of parasitic capacitance in the battery system are seen and discussed. An example implementation of the findings in a switching model is presented as well as a simple design application example.