Electric vehicle (EV) lithium battery fires in facilities such as factories, warehouses, parking structures and ships, though rare, are lethal and destructive when they happen, but remote monitoring of battery temperature can provide a timely warning of a developing problem, writes Peter Donaldson.

“Temperature rise is one of the main reasons for thermal runaway in Li-ion batteries, and it is proven that if you can identify the temperature rise itself, you can stop the thermal runaway and the fire it causes,” says Harish Pingali, senior manager, global product management at Brady Europe, Middle-East & Africa, which offers remote temperature monitoring based on radio-frequency identification (RFID) technology.

The system includes passive ultra-high frequency (UHF) RFID tags with integral temperature sensors, remote readers that can be mounted around a facility and networked, and software that logs temperatures, identifies trends and sends alerts to facility managers.

In sensing tags, the sensor is directly attached at the inlay level. Pingali explains: “The reader initiates the communication and the RF emitted by the reader antenna powers the tag, which automatically activates the sensor on the inlay as well.”

The sensor reading is incorporated into the signal sent back to the reader by the tag. 

The tags/labels can be fixed to battery cells, modules, pack casings or packaging, and they are offered in “on-metal” variants with backplane materials that absorb unwanted RF reflections from the metal battery case (for example, to minimise multipath interference) and antennas optimised to ensure stable signal transmission.

Conventional, “off-metal” versions are also offered for applications where metal-related interference is not a problem. Even when fixed to cardboard packaging around a metal pack casing, the on-metal tags can still detect temperature rises, which might indicate a problem.

“If the temperature rises by more than 0.5 C, then an alert must be sent, but anything less than that is considered just a minor variation,” Pingali says.

The system operates completely independently of the batteries’ own BMS, adding value wherever the battery is not in motion, from production and warehousing to recycling.

“This also ties into digital-product passport discussions as well,” Pingali says. “The tag on the battery could also be used as a passport into which you can encode all kinds of information.”

Readers interrogate tags about twice per second, which is more than often enough to identify a problem trend. “If, in a 10-minute interval, the temperature is rising, you need to take action,” he explains.

Combined with readers capable of interrogating multiple tags simultaneously, this provides the required accuracy with a lower total cost of ownership than alternative wireless monitoring options, he adds. “Depending on the size, we can cover three or four batteries per antenna.”

Pingali notes that sensing RFID tags are available from leading manufacturers, including Avery Dennison, Confidex and Omni-ID, along with Brady. Hardware and software is integrated by Brady to create “solution blueprints” that partners can then fine-tune and implement with customers.

Initial deployments with six undisclosed customers, all Li-ion battery manufacturers, have reached the stage where they are ready to be scaled up, and three of them have already, Pingali adds.