Adaptive thermal management for portable system batteries by forced convection cooling

Cycle life of a battery largely varies according to the battery operating conditions, especially the battery temperature. In particular, batteries age much faster at high temperature. Extensive experiments have shown that the battery temperature varies dramatically during continuous charge or discharge process. This paper introduces a forced convection cooling technique for the batteries that power a portable system. Since the cooling fan is also powered by the same battery, it is critical to develop a highly effective, low power-consuming solution. In addition, there is a fundamental tradeoff between the service time of a battery equipped with fans and the cycle life of the same battery. In particular, as the fan speed is increased, the power dissipated by the fan goes up and hence the full charge capacity of the battery is lost at a faster rate, but at the same time, the battery temperature remains lower and hence the battery longevity increases. This is the first work that formulates the adaptive thermal management problem for batteries (ATMB) in portable systems and provides a systematic solution for it. A hierarchical algorithm combining reinforcement learning at the lower level and dynamic programming at the upper level is proposed to derive the ATMB policy.