Aclara AMR units working 25 years with Tadiran Lithium battery
By Sol Jacobs, Tadiran Batteries
Twenty-five years ago, Aclara™ (formerly Hexagram,Inc.) began installing hundreds of thousands of battery-powered automatic meter reading (AMR) devices for the utility market. Powered by a single Tadiran TL-2100 AA-size lithium thionyl chloride battery, virtually all of these decades-old AMR devices are still operating on their original battery, with laboratory confirming that they had retained nearly 25 % of their original capacity.
Aclara has since introduced a newer generation of STAR® Network wireless fixed-network AMR systems using an upgraded Tadiran TL-4903 “XOL” (eXtended Operating Life) AA-size lithium thionyl battery, which features 33 % higher capacity (2.4 Ah vs. 1.8 Ah) and lower self-discharge than the TL-2100 battery. Aclara selected the TL-4903 (equivalent to SL-860) battery based on superior performance characteristics, including higher energy density, higher capacity, a temperature range of 55 ºC to +125 ºC, and 20+ year service life.
Longevity leads to profitability
STAR® network meter transmitter units (MTUs) are capable of providing multiple daily readings using narrow-band radio frequency to communicate with data collection units (DCUs) strategically positioned on buildings or utility poles located approximately 1 to 2 miles apart. These units combine intelligent energy-saving design with advanced lithium thionyl chloride battery chemistry to deliver proven 20-year service life. To conserve energy, STAR MTUs do not employ a receiver to listen for a “wake-up” transmission. Instead, a timer initiates data transmission at programmed intervals. Use of one-way transmission also results in a less complex, lower cost system.
The life cycle savings that can be achieved with a 20+ year AMR unit are substantial compared to a unit with an expected service life of 7 to 10 years, as cost savings begin to accrue in year 7 and continue throughout the 20-year product life cycle. For example, a utility with 5,000 service connections could realize up to $200,000 in total cost savings over a ten year period by eliminating all battery changeouts during that 10-year period, assuming that the cost of each battery changeout is approximately $40 per site. If a second round of battery changeouts were eliminated over a 20-year period, the potential $400,000 in savings could be achieved for every 5,000 service connections. These savings would be above and beyond the labor savings associated with eliminating visual meter reading.
Lithium batteries are not created equal
Through comparative analysis, Aclara confirmed that lithium thionyl chloride batteries are not created alike, as they performed comprehensive in-house and independent tests on competing battery technologies claiming to offer equivalent battery performance, but to date have not qualified any other brand because none could match the quality of construction and electrolyte purity of Tadiran batteries.
The performance of a lithium thionyl chloride cell can vary based on the self-discharge rate, which is governed by the chemical composition of the electrolyte, the manufacturing processes used, as well as mechanical and environmental considerations. Self-discharge can be negatively affected by high levels of impurities in the electrolyte. Extreme temperatures can also reduce battery performance by affecting voltage and self-discharge rate.
Battery performance can be further hindered by impedance, which results from the internal resistance created by the electrolyte, the anode, and the cathode. Tadiran controls impedance by blending special additives into the electrolyte. Tadiran also employs fully automated manufacturing techniques to ensure unparalleled lot-to-lot consistency in large volume production. Product quality is further verified by ISO-9001:2000 certified quality systems, including fully documented and verifiable test results for parameters such as battery pulse, low-temperature pulses, discharge and repeatability.
Aclara’s remarkable feat of 25+ year service life demonstrates the synergistic possibilities of combining innovative product design combined with advanced lithium battery technology to achieve higher ROI by reducing the total cost of ownership.