Beware of 'Summer Battery' Hazards: NITE-Supervised Survey Reveals 6 Dangerous Mobile Battery Habits

INFORICH Inc. (Headquarters: Shibuya-ku, Tokyo; Group CEO: Hironobu Akiyama; hereinafter "INFORICH"), operator of the mobile battery sharing service "CHARGESPOTTM," conducted a nationwide survey under the supervision of the National Institute of Technology and Evaluation (hereinafter "NITE") on "Dangerous Mobile Battery Habits in Summer," targeting 1,406 mobile battery owners across Japan.

As temperatures rise and outdoor activities increase, the risk of incidents such as battery fires and malfunctions also grows. In response, NITE, which investigates and analyzes product accidents, has launched a public awareness campaign themed "Beware of Summer Battery (Natsu-bate)," warning consumers about safe battery handling during hot months.

This survey, conducted under NITE's supervision, presented the "Six Dangerous Mobile Battery Habits in Summer" and surveyed users to uncover real-world behaviors. The results revealed that many users unknowingly engage in risky practices—such as leaving batteries in high-temperature environments, exposing them to impacts like drops, or water exposure—that could lead to fires or malfunctions.

【Survey Summary】

▶ High-Temperature Risk: Over 40% of respondents reported leaving or using their mobile batteries in environments prone to overheating, such as inside cars during summer or while charging.

▶ Impact Risk: About 20% have dropped their battery on the ground; approximately 7% continue using batteries despite visible swelling or damage.

▶ Safety Awareness: Around 18% either never checked or do not know whether their battery is subject to a recall.

【Background Data】NITE's Warning on the Reality of "Summer Battery"

According to NITE's press release issued on June 26, 2025, titled "Beware of 'Summer Battery (Natsu-bate)'", incidents involving lithium-ion battery-powered devices have been increasing annually, peaking during summer months.

From 2020 to 2024, 1,860 accidents occurred, with approximately 85% involving fires.

Incident numbers rise with temperature, peaking in August (228 fire incidents, the highest).

Mobile power banks accounted for the highest number of incidents by product category (361 cases); in 2024, incidents more than doubled compared to 2022.

Source: NITE "Beware of 'Summer Battery (Natsu-bate)'"

https://www.nite.go.jp/jiko/chuikanki/press/2025fy/prs250626.html

Based on these findings, NITE has identified six key hazardous practices to avoid when handling mobile batteries during summer.

【NITE-Supervised】Six Dangerous Mobile Battery Habits in Summer

Category

Hazardous Practice

Risk

1

High Temperature

Leaving the battery in a car during summer or under direct sunlight

Rupture or fire due to abnormal heat buildup

2

High Temperature

Using while charging in heat-trapping conditions (e.g., inside pockets or bags)

Fire due to poor heat dissipation and rising internal temperature

3

Impact

Subjecting the battery to strong impacts (e.g., dropping, compression, including in back pockets or bags)

Smoke or fire due to internal short circuits

4

Impact

Continuing to use a swollen, deformed, or damaged battery

Fire ignited by flammable internal gases

5

Water Exposure

Using while wet or near water; continuing to use after submersion

Short circuit or fire due to internal corrosion

6

Safety Awareness

Using without checking if the battery is subject to recall

363 annual accidents linked to recalled products

INFORICH conducted its own survey of 1,406 mobile battery owners nationwide, revealing that many unknowingly engage in the very behaviors warned against by NITE.

Q1. [High-Temperature Risk] Locations where users have left (or situations in which they have used) their mobile batteries (multiple responses, n=1,406)

1

Kept in pants pocket or bag while charging smartphone (heat-trapping condition)

23.97%

337

2

Inside a car during summer

(on dashboard, seat, footwell, storage area)

19.27%

271

3

Left or charged in a bag or pocket outdoors under direct sunlight

9.25%

130

4

Near windows at home or office (where direct sunlight reaches)

9.17%

129

5

Outdoors under direct sunlight (e.g., park benches, tabletops)

4.98%

70

6

On hot asphalt, concrete, or sandy beaches

3.49%

49

※Excludes those who answered none

When asked about past exposure to high-temperature risks (e.g., heat buildup, direct sunlight), many respondents reported situations where heat could accumulate during charging or storage. Incidents such as leaving batteries in cars during summer or using them in direct sunlight indicate that many users handle batteries in inappropriate conditions. Since mobile batteries generate heat during charging and discharging, it is crucial to avoid prolonged use in poorly ventilated environments or when in direct contact with other objects. As summer approaches, please take care not to store or leave batteries in hot locations such as inside vehicles or under direct sunlight.

【NITE Comment】

Incidents involving lithium-ion battery-powered devices, including mobile power banks, tend to increase during summer. According to accident data reported to NITE, the monthly average number of incidents from June to August is about twice that from December to February. Leaving batteries in cars, using or storing them under direct sunlight, or using them in heat-trapping conditions during charging accelerates battery degradation and may lead to internal short circuits or thermal runaway. As summer brings conditions closer to those that trigger accidents, it is essential to avoid using or storing batteries in high-temperature environments.

Q2. [Impact/Compression Risk] Battery handling behaviors users have experienced or currently practice (multiple responses, n=1,406)

1

Dropped the battery on the ground from hand or desk (strong impact)

18.78%

264

2

Stored in a bag alongside hard objects such as metal water bottles, tumblers, or heavy books (risk of compression or impact)

11.38%

160

3

Placed in back pocket of pants and sat down

11.38%

160

4

Continued using a battery that is slightly swollen or has scratches, dents, or cracks on the casing

6.90%

97

※Excludes those who answered none

Regarding impact and compression risks, "dropping the battery on the ground from hand or desk (18.78%)" was the most common. This was followed by "storing in a bag with water bottles or heavy books (11.38%)" and "sitting down with the battery in back pocket (9.46%)." Damage to internal cells from impact or compression can lead to short circuits and fires. Additionally, 6.90% (97 respondents) reported continuing to use batteries despite visible swelling or casing damage, highlighting a tendency to overlook signs of deterioration.

【NITE Comment】

Lithium-ion batteries may suffer internal structural damage from strong impacts such as drops or compression. Even if no immediate abnormality is observed, this damage can lead to internal short circuits during subsequent use or charging, resulting in smoke or fire. Products showing signs such as swelling, casing scratches, deformation, or cracks may already have damaged internal battery cells. Continuing to use such products is extremely dangerous; usage should be stopped immediately upon detecting any abnormalities.

Q3. [Water Exposure and Other Risks] Battery handling behaviors users have experienced or currently practice (multiple responses, n=1,406)

1

Never checked or do not know whether their mobile battery is subject to recall

17.99%

253

2

Kept in pocket of sweaty or wet clothes during exercise

6.90%

97

3

Used outdoors in the rain or with wet hands

6.69%

94

4

Got wet or submerged, but continued using after drying

5.83%

82

5

Used near pools, beaches, or rivers (where splashing may occur)

5.33%

75

6

Know their battery is subject to recall but continue using it

0.92%

13

※Excludes those who answered none

Regarding risk-related behaviors, the most common response was "never checked or do not know whether their battery is subject to recall" (17.99%). A notable number also reported behaviors that could lead to short circuits due to water exposure, such as "kept in wet clothing pockets during exercise (6.90%)" and "used while wet during rainy weather (6.69%)."

【NITE Comment】

Many smoke and fire incidents involving mobile batteries are linked to recalled products. Recalled batteries may malfunction not only during charging but also due to shocks during transport. If such an incident occurs on public transit or indoors, it could endanger others. Additionally, even if a device appears dry after water exposure, moisture may remain inside, leading to internal short circuits later. It is important to regularly check whether your device is subject to recall and to avoid continued use of any device that has been submerged or significantly wet.

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About This Survey

The survey questions were developed under NITE's supervision, based on accident data and investigative findings related to lithium-ion battery-powered devices collected by the institute. NITE experts have provided comments on the survey results, offering safety advice and highlighting accident risks. These comments are intended solely for consumer safety education and do not endorse any specific service, company, or product.

Summary

This survey revealed that many people unknowingly subject their mobile batteries to risky usage conditions. In particular, "heat" and "impact" are major factors in lithium-ion battery fires. If your battery is old or shows signs of swelling or other abnormalities, stop using it immediately and dispose of it properly according to your local municipality or manufacturer guidelines.

CHARGESPOT Safety Standards

CHARGESPOT mobile batteries comply with Japan's Electrical Appliance and Material Safety Law (PSE) and adhere to international safety standards. Additionally, CHARGESPOT uses IoT technology to monitor all stations and batteries in real time, 24/7, enabling prompt recovery and replacement upon detecting anomalies, ensuring safe service operations.

Moreover, leveraging over eight years of accumulated rental usage data since service launch, CHARGESPOT has continuously enhanced its safety management logic and improved its products. Based on insights drawn from vast operational experience, the company has built a proprietary management system capable of early risk detection and prevention.

CHARGESPOT aims to create a society where everyone can go out safely by reducing risks associated with personal ownership and management of mobile batteries (such as degradation and fire hazards) and offering a new usage model—"borrowing" safe batteries when needed.

【Survey Overview】

Survey Name: Survey on Mobile Battery Ownership Survey Period: June 10–12, 2026 Target Respondents: Mobile battery owners nationwide Valid Responses: 1,406 Survey Method: Online survey

About the CHARGESPOT Service

CHARGESPOT is Japan's number-one mobile battery sharing service. Renting is simple: just scan the QR code on the battery station using the CHARGESPOT-compatible app. With approximately 60,000 units installed across all 47 prefectures in Japan, the service is expanding globally into Hong Kong, Taiwan, China, Thailand, Singapore, Macau, Australia, and Italy. ※As of March 2026

【How to Use】

· App Name: CHARGESPOT

· Download here: https://go.onelink.me/GQjX/cc9f2407

About INFORICH Inc.

· Address: 10th Floor, Aoyama Oval Building, 5-52-2 Jingumae, Shibuya-ku, Tokyo 150-0001

· Representative: President and Group CEO Hironobu Akiyama (Chen Ri Hua)

· Founded: September 2015

· Company Website: https://inforich.net/