Are lithium batteries a fire risk?

With constant news articles about lithium batteries causing fires and mass confusion over how safe or dangerous they are we wanted to write something to inform you of the facts. This article talks about the differences between a cell and a battery, how they can catch fire, and what you can do to prevent that.

Cells vs Batteries

Let’s do some myth-busting and clarify some misunderstandings. At Cell Supply, we actually only sell ‘cells,’ which are components of batteries, not batteries themselves. Quality cells have protective rings and wraps so that the exposed positive and negative terminals are at either end of the cell, making them largely impossible to short circuit on their own. Cells become a battery when placed in your device, which manages the discharge and recharge process. Ultimately, the device must connect the positive and negative terminals to make it work, increasing the risk of a short circuit and the likelihood of those headline-grabbing fires.

Top Six Fire Risks of Lithium Batteries/Cells

Lithium-ion cells can pose a fire risk under certain conditions. These cells are commonly used in various devices, including laptops, flashlights, power banks, and electric vehicles. While they are generally safe when used and handled properly, there are factors that can increase the risk of fire or thermal runaway, including:

  1. Overcharging: Overcharging a lithium-ion cell can cause it to overheat and potentially catch fire. Most modern devices have a battery management system, and most chargers have built-in protections to prevent overcharging. However, using low-quality or damaged chargers can bypass these safeguards.
  2. Over-discharging: Allowing a lithium-ion cell to discharge too much can also lead to problems. When the voltage drops too low, it can cause the cell to become unstable and potentially catch fire during subsequent charging.
  3. Physical Damage: Physical damage to the cell, such as punctures or crushing, can compromise the integrity of the battery’s internal components and lead to thermal runaway.
  4. High Temperatures: Exposure to high temperatures or operating the battery in extreme conditions can increase the risk of thermal runaway. Lithium-ion batteries are sensitive to temperature, and overheating can lead to a fire.
  5. Manufacturing Defects: In rare cases, manufacturing defects can lead to internal short circuits or other issues that increase the risk of fire.
  6. Short Circuit: Cells are difficult to short, but not impossible. We have seen reports of someone right here in NZ suffering from burns after they put a loose cell in their pocket with keys and other metallic objects, which effectively connected the positive and negative terminals on the cell, causing the cell to overheat.
Always use the charger designed for your battery

While cells are pretty straightforward, a high-quality charger will assume the cell is completely dumb and take care of the entire charge. When it comes to batteries for specific devices, we are seeing an increase in fires from users using incorrect chargers for lithium batteries. While it’s important to have overcharging, over-discharging, and temperature protection for batteries, where this protection lies depends on the manufacturer.

For example, one e-bike might have protection in the batteries, while another will have it in the charger. So if you plug a charger that assumes the battery takes care of the charging into a battery pack that assumes the charger takes care of the charging, you are dramatically increasing the risk of fire.

“Just because a charger designed for another battery fits and it looks like it’s charging doesn’t mean it’s safe.”

To minimize the risk of fire associated with 18650 or 21700 cells and lithium-ion batteries in general, it’s essential to follow these safety guidelines:

  • Use quality chargers for cells that have built-in protection circuits.
  • Use the correct charger for batteries.
  • Avoid overcharging or discharging the batteries beyond their recommended voltage range.
  • Store lithium-ion batteries in a cool, dry place and avoid exposing them to extreme temperatures.
  • Inspect batteries for physical damage and replace damaged ones promptly.
  • Use battery cases or holders to prevent short circuits when transporting or storing loose batteries.
  • Be cautious when using third-party or counterfeit batteries, as they may not meet safety standards.

Overall, while 18650 cells and lithium-ion batteries can be a fire risk if mishandled or used improperly, following safety guidelines and using reputable products can help mitigate these risks.

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