Solving Power Supply Issues of Cold Chain Sensor TagsDevelopment of Low Temperature Sensor Tag Causes Headaches

Background

Due to the Covid-19 pandemic, there is increasing focus on the importance of cold chains (low temperature distribution networks)* as an essential part of safe vaccine transport. The client, a manufacturer of electronic components, was asked to develop a sensor tag unit for cold chain use by one of its customers and was flat-out gathering information.

*Cold chain: a system for ensuring that pharmaceuticals, foods, and other products requiring temperature control are distributed under consistent conditions and at the appropriate temperature (chilled, refrigerated, or frozen) from the time of manufacture, during transit, and until consumption. Cold chains play an important role in the transportation of not only vaccines but also foods, drinks, chemicals, and pharmaceuticals.

Problems

Conventional Batteries Unreliable at Low Temperatures

While the manufacturer was experienced in sensor development, it had never developed a sensor for temperature monitoring for cold chains. In cold chains, sensor tags need to be able to collect temperature data in real time for transmission over wireless communications in a reliable manner, even at low temperatures of -20℃ and below. No matter how many prototypes the manufacturer built, however, they found battery drain was accelerated at low temperatures, leaving batteries unable to supply the current necessary for wireless communications. None of the non-rechargeable batteries evaluated came anywhere near being commercially viable. Short battery lives and the resultant inability to ensure reliable wireless communications also meant the sensor tags could not convey critical temperature data or issue warnings in the event of an anomaly. The development team continued to search for a way to enable reliable battery operation in cold environments.

Increasing Battery Capacity Made Miniaturization Difficult

On top of that, the power supply was not the only issue. The manufacturer also needed to solve its size issues quickly. Because cold chains tend to involve refrigerated containers of varying sizes, the manufacturer wanted the sensor tags to be thin and compact. However, with increasing capacity the only way to extend the lives of the non-rechargeable batteries used, it was difficult to make the sensor tags any thinner or more compact. While the team did consider switching to rechargeable batteries, they soon realized that the need to design charging and power supply circuits and include dedicated charging ICs would affect the size of the sensor unit. Unable to come up with a product concept that would satisfy the customer’s requirements, the development team were at their wit’s end.

Main Issues

No non-rechargeable battery would have been commercially viable in the cold chain sensor tag because these batteries run out too quickly at low temperatures to reliably drive wireless communication functions.
The only way of achieving sufficient capacity would have been switching to a larger capacity non-rechargeable battery, but that would have prevented the team from making the sensor tags thinner or more compact.

The Solution Enabled by EnerCera battery