E-scooter and e-bike lithium-ion battery fires

Summary of the work

Electrical Safety First is a campaigning charity that aims to reduce deaths and injuries caused by electricity in UK homes. They commissioned these tests as they were concerned at the increasing number of incidents from these types of batteries. The tests on the batteries were performed by:

• Crushing them,
• Penetrating them with sharp objects such as could happen in a collision,
• Dropping them from height,
• Overcharging them with an incorrectly specified charger,
• Placing the battery terminals next to each other to create a short circuit, and
• Heating them up by placing them close to a heat source.

During some of the tests the cells inside the batteries exploded, releasing toxic gases, flames, energetic sparks and enough smoke to rapidly fill a standard-sized hallway in a house. In some cases, ignited cells were projected throughout the test area, with the potential to set fire to other materials. This happens because when battery cells fail, they go a state of ‘thermal runaway’ during which the heat from one cell ignites those next to it which in turn heat the next cells, and so on. 

A video summarising this work is available here and below you’ll find videos for the penetration test and overcharge test.

Penetration test

For the penetration test an e-scooter lithium-ion battery was penetrated with a 150mm long, 6mm diameter nail.  This represents an impact that leads to the casing being compromised and resulting short circuit of multiple cells. The battery was initially at room temperature but once penetrated, the surface temperature of the battery increased by 180°C in 10 seconds before the thermocouple was dislodged by the explosions.

Overcharge test

For the overcharge testa charger with higher power specifications was used to charge the battery. This is a common error as members of the public are known to charge different e-scooters (with differing charge specifications) with the same charger or have replaced chargers with the wrong type.  The battery stopped charging however the temperature was gradually increasing and 40 minutes later went from 52°C to 501°C in 8 seconds.

For more safety information

On their web-site Electrical Safety First recommend, amongst other things, to:

• Regularly check the condition of the battery;
• Stop using/charging the battery as soon as you notice any damage and replace it;
• Only use the charger supplied with the battery;
• If the original charger is not available, obtain a replacement from the original manufacturer;
• Don’t leave items on charge continuously;
• Charge your batteries in a safe place;
• Ensure that you have adequate early warning systems in place (in case of fire).

Next steps

Whilst this work has highlighted the extent of dangers associated with lithium-ion battery fires there is still lots of work that needs to be performed to provide sufficient protection in the future as the number of these batteries will only increase with time.

If you are interested in performing collaborative research work (see article) or private work in this area, please do not hesitate to get in touch. 

Thank you to Electrical Safety First for supporting this important work to raise awareness of the dangers associated with lithium-ion batteries used in e-scooters and e-bikes.