Proving the Business Case for the Internet of Things

Murata coin cell batteries suit LoRa and Sigfox devices

Steve Rogerson
November 8, 2018

Japanese component maker Murata has developed two high drain and extended temperature lithium coin cell batteries for low-power wide-area (LPWA) communications devices using LoRa and Sigfox networks.
Building on Murata’s standard and heat-resistant ranges of CR battery sizes, the high current type, designated suffix R, has twice the maximum pulsed discharge rating of conventional models at 50mA (three seconds at 2V or higher, at 50% nominal capacity, 23°C) and three times the discharge time (45mA pulsed for three seconds, 23°C).
These characteristics make the parts suitable for LPWA communications devices, including LoRa and Sigfox with their high peak current requirements. Available in CR2032 and CR2450 sizes with 3V nominal rating, the cells have nominal capacities of 200 and 500mAh, respectively, for discharge down to 2V.
Extended temperature types designated suffix X are available in package sizes CR2032, CR2450, CR2477 and CR3677 and have an extended operating temperature range of -40 to +85°C compared with standard types rated at -30 to +70°C.
The wider temperature range better matches the typical ratings of electronic parts in more challenging environments such as automotive, with a better cost-performance figure compared with types rated to +125°C. Stored charge loss at high temperature is low over time and the CR3677X model is said to deliver the highest capacity of any lithium coin cell, enabling smaller and thinner devices.
Although previously lithium cells have been seen as back-up supplies, these ranges open up applications where the battery is the main power source. Typical uses are in the IoT, automotive and factory automation where LPWA networks are becoming common with sensors requiring local power supplies. The higher temperature range particularly suits outdoor applications such as smart meters, security and automotive, where the cells can replace conventional cylindrical types.
“Semtech’s LoRa RFIC SX1261 needs an approximately 25mA power supply current at 3V supply voltage and 42mA at 1.8V in order to achieve an output of Arib-T108-compliant 20mW,” said Vivek Mohan, director of IoT at Semtech. “The LoRaWan standard defines the maximum transmit time at three seconds. With Murata’s new high current type lithium coin cell battery, up to 50mA and 3s of current can be used, making it promising for LoRaWan-compatible small sensor nodes.”
The battery range underlines Murata’s commitment to the growth of IoT, leveraging the four decades of technology development of Sony’s battery operations, which Murata acquired in September 2017.
Samples are available now and mass production is scheduled to begin in January 2019.