Protection Circuit Model (PCM) when assembled together to form a battery. The PCM will generally provide the battery with overcharge/discharge protection, short circuit protection, current limitation, and voltage and current balancing in each cell. All of these factors are important in obtaining the maximum output and longest lifecycle from a rechargeable lithium battery. These notes will discuss the need for and configuration of a PCM, the advantages and disadvantages of these configurations, and step-by-step instructions for the construction of a rechargeable lithium battery with an onboard PCM.