Assault on batteries

Nov. 30, 2007

Mobiles can be used to track temperature, vibration, voltage and electric power of devices such as motors, lighting, HVAC and generating equipment, both for power consumption and condition monitoring purposes. “Energy usage evaluation and condition monitoring for electric machines are important in industry for overall energy savings,” says Gary Ambrosio, CEO, Sensicast Systems ( “Traditionally, these functions are used only for large motors in costly wired systems using communication cables and various types of sensors.”

Expanded condition monitoring of less-critical assets calls for easily installed, low-cost wireless sensors for temperature, power and vibration, but no one wants to be changing batteries constantly. So sensor and software companies have developed interesting alternative approaches to extending battery life or eliminating batteries altogether.

Batteries in traditional Wi-Fi devices have a useable life of only a few days. Through partnership with GainSpan, Sensicast has developed a power management system-on-a-chip that allows its Wi-Fi sensor nodes to operate for years on a single battery.

“Removing the data cable often only solves half the problem, which isn't solving anything at all,” says Niek Van Dierdonck, vice president of strategy and product management, GreenPeak ( “Batteries are a curse. When they fail, they must be replaced, and they usually go down before they are noticed.”

Alternatives include solar power where the lighting is good or vibration where it’s available, such as rotating equipment. But these power sources are constant and low.

“They don’t deliver power the way you need it,” Van Dierdonck says, “a peak for transmission, low level when sleeping.” His company has worked on the communication system to shave peaks by spreading the communication tasks over time. “We want to do this at a price point where it makes sense to add a lot of sensors,” he adds, “not just as an alternative to wired systems, but new applications where wire would be too costly or impractical.”

If more power is needed, MIT researchers recently demonstrated a practical method for wireless power transfer using magnetically coupled resonance (