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[November 2021]

Take caution in using lithium-ion batteries!

Sample cases

When charging my smartphone, I smelled something burning. Then I noticed that the charger and the smartphone jack got burned.

(man in his 60s)

I bought a foreign-made mobile battery at an online shopping site. The lithium-ion battery therein swelled up and was about to explode.

(man in his 40s)

Lithium-ion batteries, which can be charged and used repeatedly, are used for smartphones, tablet computers, mobile batteries, etc. On the other hand, it has been reported that lithium-ion batteries ignited and smoked.

Reproductive experiment on heat generation and burnout

(1) Heat generation when the charging terminal was contaminated with foreign matter

When the charging terminal was contaminated with conductive foreign matter such as pencil lead and the mobile buttery was charged, the charging terminal heated up and smoked, then the surface around the charging terminal melted (Photo 1).

(2) Heat generation when charging a smartphone in operation

A smartphone in operation was charged under the blanket to prevent heat dissipation, during which a video was played continuously on the smartphone. One hour later, the surface temperature of the smartphone rose to nearly 50 degrees C. If it contacts with human skin for a long time, for instance while sleeping, it could cause a low temperature burn.

(3) Smoke generation due to abnormality in mobile battery

Thermal runaway could be the main cause of heat and smoke generated from lithium-ion batteries. When a mobile battery was put in a bag and was powered from outside the bag to reproduce the thermal runaway, the lithium-ion battery was raised to high temperature, ejecting gas and smoke (Photo 2). In addition to the mobile battery itself, things around it were also burned and damaged.

Photo 1. Connection where the charging terminal was melted
Photo of the connection where the charging terminal was melted

Photo 2. Smoke and gas ejected from bag carried by dummy
Photo of smoke and gas ejected from bag carried by dummy

Advice for consumers

(1) When the charging terminal has become hot or smells bad, stop using it immediately. If you have noticed that a lithium-ion battery swelled, refrain from using it.

(2) The temperature of a smartphone rises when being charged or used, especially if it is in a pocket or under a blanket where the heat is kept inside. Beware of low temperature burns.

(3) In Japan, lithium-ion batteries are required to be labeled with the PSE mark, the company name, etc. Refrain from buying lithium-ion batteries if the model number and specification are unknown and the PSE mark is not labeled.