Enlightened by the 'Totally Innovative Cloud Things of Connectedness' from the theme of 2017 round Australian National Wide Cyber Security Challenge 1 , cloud back-end and the hardware devices are identified as important components for cyber security investigation. On the other hand, rechargeable Lithium-ion (Li-ion) battery packs are widely used for energy storages and back-up power supplies. There are numerous embedded sensors in the Battery Management Systems, which provide the first hand data for optimizing the collective performance of the battery packs. Therefore, these sensor nodes are the desired initial starting points for exploring the vulnerabilities and security protections to the decentralized end nodes in IoT. This paper surveys the online SoC estimation of Li-ion batteries, endeavors to understand the models, control and management of the networked rechargeable batteries. This brief aims to initiate a research on decentralized secure cloud management to the end nodes of IoT.