Toshiba Succeeds in the World’s First Demonstration of Wireless Storage Battery Monitoring Using the Bluetooth^® Low Energy Ultra-low-power Wireless Standard in Environments with Severe Radio Interference and Reflections

TOKYO—Toshiba Corporation (TOKYO: 6502) has succeeded in the world’s first demonstration (*1) of the use of Bluetooth^® Low Energy (BLE) (*2), a general-purpose, ultra-low-power wireless standard (Fig. 1), to wirelessly monitor the status of power storage modules in a battery storage system subject to severe radio interference and reflections. It was demonstrated, both theoretically and through demonstration tests in an actual storage battery system, that occurrences of system errors can be reduced to less than one per 10-year period (*3) through a unique design based on the specifications of the storage battery system.
Status monitoring of storage battery systems is normally performed using a wired connection, but this demonstration showed the possibility of wirelessly monitoring the status of system storage modules using the general-purpose BLE wireless standard. Wireless monitoring of the system condition is expected to simplify system maintenance, provide insulation measures, and improve freedom of installation, contributing to further disseminating safe storage battery systems. Toshiba will present details of this demonstration on June 22 at the international telecommunications technology conference VTC2023-Spring in Florence, Italy.

Fig. 1: Wireless monitoring of storage battery systems

Storage battery systems are essential for stably supplying electricity from renewable energy sources, and their use is increasing in a wide range of fields, including railroads, ships, and virtual power plants. By 2035, the global market for stationary storage batteries is expected to expand to approximately 4.3 times the 2020 batterycapacities.
To ensure safe operation, storage battery systems implement a cell monitoring unit (CMU) that monitors the voltage and temperature of each of the storage modules and a battery management unit (BMU) that manages them. CMU–BMU communications are normally wired, but issues such as insulation resistance, flexibility in storage battery installation, and prevention of wiring errors have created the need for wireless communications. While there have been reports of attempts to realize wireless storage battery systems through the use of proprietary communication methods, wireless monitoring based on a general-purpose wireless standard will be essential for realizing the widespread dissemination of storage battery systems with wireless monitoring. However, applying such standards has been very difficult because these wireless communications must be conducted in environments characterized by severe interference and reflected radio waves from unrelated sources.

Against this background, Toshiba has succeeded in the world’s first demonstration of wireless monitoring using BLE to realize wireless monitoring of the status of energy storage modules in battery storage systems.
In a storage battery system, 20 or more storage batteries are usually installed in a closed space, surrounded by metal, and wireless communications between each must occur within. Wireless communication requires under the assumption that signals from CMUs to BMUs in each battery will mutually interfere, and that communications are likely to be unstable due to radio wave reflections within the housing. To verify the application of BLE in such a harsh environment, Toshiba designed a system that allows one-time delays and prevents continuous delays, in accordance with the storage battery system’s monitoring cycle. Specifically, the system was designed to stop the charging and discharging of energy storage modules when communication fails over three consecutive cycles, with wireless communication allowing a monitoring cycle of 100 to 200 ms (Fig. 2). Considering that the expected useful lifetime of a typical stationary lithium-ion battery is approximately 10 years, the company set a goal of suppressing errors relative to the monitoring cycle (i.e., communication delay beyond the monitoring cycle), to less than 10^-4. Using a storage battery panel with storage modules installed, two BLE modules were installed in each BMU, and 11 CMU-side BLE modules are wirelessly connected for each BMU-side BLE.
Communication delay measurements over four days showed that a monitoring cycle of about 160 ms can reduce communication delays to less than 10^-4. For BLE communications, signal interference was modeled with respect to the desired signal and showed that the delay characteristics can be explained through probability calculations (Fig. 3). Such mechanistic analyses enable prediction of delay characteristics and assure reliability when the number of storage batteries increases.
From this demonstration, Toshiba expects to be able to construct storage battery systems using energy storage modules equipped with BLE communication functionality that are operable for long periods of time.

Fig. 2: Storage battery system monitoring cycle

Fig. 3: Measured and calculated values (CCDF: complementary cumulative distribution function)

Toshiba will continue to carry out research and development of energy storage modules with wireless monitoring functions to contribute to the realization of safer battery storage systems.

*1: This was the world’s first demonstration in which a cell monitoring unit (CMU), which monitors the voltage and temperature of each storage module in a storage battery system, and a battery management unit (BMU), which manages the CMU, were successfully connected via Bluetooth Low Energy in an experiment using an actual storage battery system (as of June 22, 2023, according to a Toshiba survey).
*2: Bluetooth Low Energy is an extension of the Bluetooth standard, added in Bluetooth 4.0. Its most significant feature is its ultra-low power consumption, and it is used in a wide range of applications including consumer electronics, automobiles, and industrial applications. Bluetooth is a registered trademark of Bluetooth SIG, Inc.
*3: Lithium-ion batteries have a useful life of around 10 years, and the communication aspects of this development were designed accordingly.
https://www.global.toshiba/jp/news/corporate/2017/03/pr0801.html
*4: “Current Status and Issues in the Storage Battery Industry,” Nov 18, 2021, Ministry of Economy, Trade and Industry
https://www.meti.go.jp/shingikai/mono_info_service/chikudenchi_sustainability/pdf/001_s01_00.pdf(3.6MB)