ZigBee network technology has been used widely in different commercial, medical and industrial applications, and the importance of keeping the network operating at a longer time was the main objective of ZigBee manufacturers. In this paper, ZigBee battery characteristics and operation has been researched extensively and a mathematical modeling has been applied on existed practical data provided by Freescale semiconductors Inc [1], and Farnell [2]. As a result a mathematical optimized formula has been established which describes battery characteristic and voltage behavior as a function of time, and since ZigBee node batteries has been the core objective of this research work, a decline in battery voltage below 50% of battery capacity could influence and degrade ZigBee network performance.