I am using Xbee S2 and Xbee Pro device, how can i use battery configuration for powering the device. can i use 1.2V chargeable battery in series and make 3.6V and apply to module, but i have query what if i recharge the battery it will then have 1.4V each when gets full charge. Then all will contribute to 4.2V, will it damage the module. also i have concern for long battery life application. kindly suggest method to power device with long life in considering.