Powering AMI

By Sol Jacobs

The smart meter market has exploded as utilities increasingly deploy advanced metering technology to boost operational efficiency and improve bottom line performance.

Roughly half of all water meters in North America are now equipped with Automated Meter Reading (AMR) and Advanced Metering Infrastructure (AMI) devices. The advent of wireless two-way communications has accelerated this transformation process, with smart meters becoming more feature-rich, requiring lithium batteries to deliver enhanced power and performance without sacrificing long-term reliability.

The vast majority of wireless AMR/AMI meters are powered by lithium batteries because they offer the highest specific energy (energy per unit weight) and energy density (energy per unit volume) of all existing battery chemistries. One reason for lithium’s high energy density is its large electric potential, which exceeds that of other metals, and which produces the high voltages typical of lithium batteries (2.7 to 3.9 VDC). Lithium cells use a non-aqueous electrolyte, which enables certain lithium batteries to operate in extreme temperatures (-55 to 125 degrees Celsius).

Of the different types of lithium batteries commercially available, Bobbin-type lithium thionyl chloride (LiSOCL2) batteries are the preferred choice for AMR/AMI applications. Bobbin cells consist of an outer cylinder made of lithium metal and an inner electrode that is reminiscent of a bobbin of thread, which permits a greater volume of electrolyte within each cell, resulting in greater capacity. Bobbin cells also feature an extremely wide temperature range and very low annual self-discharge (as little as 1 percent per year, depending on the manufacturer).

Aclara (formerly Hexagram), began using bobbin cells to power AMR meters back in 1984. While many of these early devices are being replaced by upgraded systems capable of advanced two-way communications, these older units still retain plenty of available capacity and are still operational after 28-plus years on their original LiSOCl2 batteries.

The proven track record of LiSOCl2 batteries allows today’s AMR/AMI equipment manufacturers to offer longer term performance contracts that enhance the cost feasibility of large scale upgrades to deploy networked infrastructure that enhances customer service, speeds billing and permits continuous monitoring of demand and usage.

PulsesPlus Batteries for Two-way Communications

AMR/AMI networks are becoming increasingly complex and feature-rich, exemplified by ‘On Demand’ two-way radio frequency (RF) communications that require high current pulses for data gathering and transmission. To address this need, Tadiran developed the PulsesPlus battery, which combines a standard bobbin-type LiSOCL2 battery, which is ideal for delivering low background current, along with a patented Hybrid Layer Capacitor (HLC), which delivers high current pulses during data gathering and transmission. To extend battery life, the meter remains in a sleep — or standby — state when inactive.

Another unique feature of the PulsesPlus battery is that it allows devices to be programmed to provide low battery status alerts. PulsesPlus batteries are available in a 3.6V system that indicates when approximately 95 percent of the battery’s capacity has been exhausted and a 3.9V system that indicates when approximately 90 percent of available battery capacity has been used up.

The value of an end-of-life indication can be enormous. For example, the Water and Sewer Commission of Springfield, Mass. installed a network of approximately 44,000 AMR meters. After just a few years of operation, the commission determined it was necessary to begin replacing 4,000 batteries annually at a projected cost of $9.2 million. Concerned that their labor force could be potentially overwhelmed by a rapid, system-wide battery failure, the commissioners took the preemptive step of replacing perfectly good batteries so as to avoid the chaos of having their meter reading and billing systems disrupted by large-scale battery failures. Use of proven long-life lithium batteries, in combination with AMR/AMI meters programmed to provide automatic low battery status alerts, could have avoided this costly process.

Tadiran recently introduced another technology, Tadiran Rapid Response TRR Series batteries, which do not require the use of an HLC but still deliver high capacity and high energy density without voltage or power delay.

When a standard LiSOCL2 battery is first subjected to load, voltage can drop temporarily, and then return to its nominal value. TRR Series batteries virtually eliminate this voltage drop as well as voltage drop under pulse (or transient minimum voltage level). The final result is zero delay during the voltage response. These unique attributes enable TRR Series batteries to utilize available capacity more efficiently, thus extending the operating life of the battery by up to 15 percent under certain conditions, especially in extremely hot or cold temperatures.

Mueller Systems Mi.Net AMR/AMI Network Infrastructure

An ideal example that combines advanced AMR/AMI technology with a PulsesPlus battery is Mueller Systems’ Mi.Net Infrastructure Network for utilities. The network offers a comprehensive solution that integrates the entire meter-reading-to-billing process, allowing utilities to link meters, distribution sites and control devices into a single, flexible and scalable data network.

The Mi.Node water meter interface unit provides full, two-way communications between the Mi.Net System’s Mesh/Fixed AMI system and the smart meter. Data from the meter is temporarily stored within Mi.Node?s internal memory, then transmitted ‘On Demand’ or at specified intervals via an unlicensed radio frequency channel to a Mi.Gate collector, which relays the data to the Mi.Net System?s host server.

Mi.Node interface units are often installed in underground pits, so multiple moisture barriers are required to provide a watertight solution. This robust construction, combined with Tadiran’s proven 20-year technology, enables Mueller Systems to confidently offer a 20-year warrantee. Mi.Node interface units can also be programmed to provide automatic low battery status alerts for scheduled battery replacements, which can extend the operational life of the Mi.Net System well beyond the 20-year warranty period, further enhancing the long-term value of the AMR/AMI network investment.

Another major benefit of the Mi.Net System is enhanced employee safety. Instead of having to collect meter readings by entering harsh environment such as basements or subterranean meter boxes, utility employees can now safely collect meter readings from their office or by driving in close proximity to meters. Also, in the event of a service disconnect or reconnect, two-way ?On Demand? communication, such as through Mueller Systems’ 420 RDM, allows customer service and accounting personnel to handle the entire process remotely, thus protecting employees in the field from potentially hostile encounters with customers.

The PulsesPlus battery is also powerful enough to support ‘On Demand’ two-way communications, allowing Mi.Node interface units to track hourly water consumption, identify potential tampering as well as provide automatic notification, including email alerts if excessive usage or potential leaks are detected.

The illustrative example of Mueller Systems? Mi.Node interface unit demonstrates how advanced lithium battery technology is contributing to a “smarter” smart grid that enhances utility customer knowledge and satisfaction, utility employee safety, productivity and bottom line performance through increased operational efficiency. As smart metering technologies continue to advance, lithium battery-powered solutions will continue to play a critical role in support of future innovation.

Sol Jacobs is vice president and general manager for Tadiran Batteries.

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