Beware of Increased Risks of Mobile Batteries in Summer

The Mobile Computing Promotion Consortium (hereinafter referred to as 'MCPC') has published a safety awareness page to inform users about the increased risks of mobile batteries in summer. URL: https://www.mcpc-jp.org/LiBat_2026Sum/

In recent years, there has been an increasing trend in fires involving mobile batteries and other products equipped with lithium-ion batteries. According to the public data released by the Tokyo Fire Department, the number of fires related to lithium-ion batteries in the fiscal year of Reiwa 5 was the highest ever, and the number of cases in the first half of Reiwa 6 also exceeded the same period of the previous year. Furthermore, according to the investigation by the Fire Department, the number of fires caused by lithium-ion batteries and other similar batteries has been increasing since Reiwa 4, and one of the causes of fires in mobile batteries is external impact or use and storage in high-temperature environments.

Even in daily environments, "unexpectedly high temperatures"

MCPC's confirmation revealed that even in an environment with an outdoor temperature of 29.4°C, conditions such as direct sunlight and enclosed spaces can cause a significant temperature rise in a short period of time.

・ Near a window with direct sunlight: Temperature rises to a maximum of approximately 56°C in 30 minutes

・ Inside a bag under direct sunlight: The internal terminal reaches a maximum of approximately 52.3°C, and the outside of the bag reaches approximately 60°C

As shown above, even in daily environments, conditions such as direct sunlight, enclosed spaces, and charging can lead to a high-temperature state in a short period of time. In particular, attention should be paid to the fact that the temperature can rise unnoticed in places where heat tends to accumulate, such as inside bags or pouches.

In high-temperature states, the internal reactions of the battery tend to progress, which can lead to risks such as battery degradation, expansion, heat generation, smoking, and ignition. It is important to understand that the risk can change depending on the usage environment, even with "usual usage".

Left: Left in the car

Middle: Charging in a bag (enclosed state)

Right: Using in a place with direct sunlight

Differences in "safety and quality" that are not visible to the naked eye

Even among products with similar appearances, capacities, and price ranges, there may be differences in their behavior in high-temperature environments. The background of this includes differences in the design, manufacturing process, and quality management philosophy of the products.

Specifically, temperature control design during temperature rise, protection functions against overcharging and overcurrent, quality management in the manufacturing process, inspection systems, and after-sales service systems are mentioned. While these are difficult for users to judge based on appearance alone, they are important elements that support the safety and quality of the product.

These are difficult to grasp from appearance and specifications, but they are important elements that affect behavior in high temperatures and accident risks. MCPC believes that understanding these "invisible differences" is one perspective for safely selecting products.

Usage to be particularly careful about in summer

In summer, it is important to avoid leaving items in places where direct sunlight hits, such as inside cars or near windows, and to avoid charging in places where heat tends to accumulate, such as inside bags or pouches. If you feel any abnormalities such as expansion, abnormal heat generation, inability to charge, or odor, please stop using the product and consult the manufacturer or retailer.

When selecting a product, it is important to consider not only the price, capacity, and appearance but also the manufacturing, quality management, and support systems behind the product.

About MCPC Guidelines

MCPC has developed guidelines (GL-015) for the safety and quality of mobile batteries, and is promoting the organization and visualization of information that serves as a basis for product selection from the perspectives of the manufacturing process, quality management system, after-sales service system, and the entire product lifecycle.

This guideline does not guarantee the performance or safety of a specific product. However, it aims to serve as reference information for users to make more appropriate product selections by confirming the efforts made for safety and quality, which are not easily understood from appearance or price alone.

Future Initiatives

In addition to the operation of guidelines for the industry, MCPC will continue to conduct safety awareness activities for users. In collaboration with related organizations and member companies, we will promote understanding of the safe use of mobile batteries and product selection that does not rely solely on appearance and price, based on market trends and accident information.

【About the New Logo & Catchphrase】 This logo is intended to raise awareness of potential risks that can occur in daily usage scenarios, such as leaving batteries in high-temperature environments or subjecting them to impact. After a rigorous selection process from publicly solicited works, a new logo has been decided. Details will be posted on the MCPC official website as soon as preparations are completed for public use.

【About MCPC】

MCPC (Mobile Computing Promotion Consortium, Chairman: Yasuhiko Yasuda) is a voluntary industry group established in 1997 with the aim of promoting the spread of mobile computing beyond industry boundaries. It promotes various standardization activities, including guidelines for the safe design of USB charging interfaces for smartphones, guidelines for the safe design of mobile devices, guidelines for terminal interfaces, and guidelines related to Bluetooth. In addition, through certifications such as "IoT System Technology Certification", "Mobile System Technology Certification", "Wireless IoT Planner Certification", and "Local 5G Practical Training Course", it also contributes to the spread and expansion of mobile, IoT/AI.

MCPC member companies and organizations: 169 (as of July 2026) http://www.mcpc-jp.org

"Inquiries regarding this matter"

Mobile Computing Promotion Consortium (MCPC) Secretariat

Address: 2F, Hasegawa Grebe Building, 3-5-12 Shibakoen, Minato-ku, Tokyo 105-0011

Telephone: 03-5401-1935

E-Mail: [email protected]

The press release PDF is available here. <https://www.mcpc-jp.org/press/pdf/press_20260715.pdf>

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