Certain consumer products are powered by lithium polymer cells, or laminate cells, that feature a very low profile, which is ideal for smartphones and miniaturized handheld devices. Lithium polymer batteries are not suited for industrial applications because of their limited life expectancy, and because their outer casing can be easily punctured, which causes battery leakage, internal short circuits, and premature self-discharge.
Use of an inexpensive, consumergrade rechargeable battery may be recommended if the wireless device is easily accessible for battery replacement. If the wireless device is intended for deployment in a remote, inaccessible location, however, where battery replacement is difficult or impossible, or is intended for use in extreme environmental conditions, then an industrial-grade Li-ion battery should be considered.
Here are some additional case histories involving the use of industrial-grade Li-ion batteries:
Storing Solar Power
The IPS Group manufactures solarpowered, wirelessly networked parking meters that utilize TLI Series rechargeable lithium-ion batteries for energy storage. The parking meters incorporate multiple payment system options, access to real-time data, integration to vehicle detection sensors, user guidance, and enforcement modules -- all linked to a Web-based management system (see Figure 2).
Harvesting a Magnetic Field
Southwire, a leading manufacturer of wire, cable, and associated products for the distribution and transmission of electricity, has developed a wireless line/connector sensor that supports the intelligent grid by providing realtime status of the operational electrical transmission lines. The sensor mounts directly on a bare overhead transmission conductor and harvests energy from the power line’s magnetic field, or inductive power, to measure conductor temperature, the shape of the catenary curve, and electrical current on the line. The readings are transmitted every 30 seconds to a base station using 2.4 GHz RF communication (see Figure 3).
The line/connector sensor requires sufficient line current to fully recharge, with maintenance-free backup of approximately 45 days with no line current. Since the strength of the magnetic field is constantly changing, including many periods when power drops below the threshold required for energy harvesting, Southwire deploys a TLI-1550 industrial-grade rechargeable Li-ion battery to ensure continuous operation during prolonged periods where there is no harvested power. The battery also delivers the brief energy spikes required to initiate RF communications between the sensor and the base station.
Application Requirements Dictate the Ideal Power Supply
While primary lithium batteries will power the vast majority of remote wireless devices, energy harvesting technology is proving to be a useful alternative for certain applications. Design engineers must therefore weigh all of their options, as specific requirements invariably dictate the ideal choice of power supply.
When choosing a power supply, be sure to calculate the projected total lifetime cost, including the labor and materials for future battery replacements. If the device is easily accessible and operates in moderate temperatures, then the math could favor a less expensive consumer-grade battery. If the device, however, is intended for a remote, inaccessible location, then it is highly likely that you will be best served by an industrial-grade battery.
This article was written by Sol Jacobs, VP and General Manager, Tadiran Batteries (Lake Success, NY). For more information, Click Here .