Thanks to careful power management, low power circuitry, and the operation of the Sensys Networks NanoPower protocol, the sensor battery is expected to last an average of 10 years. Several studies have specifically examined this claim, where whitepaper summaries can be downloaded from the Sensys Networks Website, www.SensysNetworks.com.
For example, as described in the Sensys Networks whitepaper, “Measurement of Sensys Networks Wireless Sensor Battery Life”, Sensys Networks investigated the remaining lifetime of battery packs obtained from three sensors that had been installed on a Texas highway for a year and a half. During the sensors’ operation, the installation site experienced air temperatures as low as 21 °F / -6.1 °C and as high as 100 °F / 37.8 °C, with a maximum daily temperature swing of 40 °F / 20.2 °C. Over the year and a half that these sensors were deployed, each sensor detected approximately 5 to 8 million vehicles, depending on what lane it was in. As part of this particular installation, the sensors were configured to transmit each vehicle detection event to the access point as it occurred, a configuration that Sensys Networks does not recommend for count stations because it does not conserve battery power. Nonetheless, analysis of the battery packs recovered from the sensors reveal an estimated total battery life of approximately 8.5 to 13.0 years.
Another Sensys Networks whitepaper, “Battery Life Analysis of the Sensys Networks Wireless Vehicle Detection System by ARRB Consulting/La Trobe University”, describes an analytical estimate of the sensor battery life developed by researchers at ARRB Consulting and La Trobe University (Melbourne, Australia). Working under contract to several Australian state road and traffic authorities, their work reveals that a sensor’s current consumption depends in part on the number of vehicles detected over its lifetime. Given the capacity of the battery used by the Sensys Networks wireless sensor and the number of vehicles that can be detected, the report concludes that the claimed average battery life of 10 years is likely to be achieved.