Safe charging of portable lithium batteries

Fires caused by lithium batteries sporadically make the news, and CERN is not immune from this phenomenon. CERN has experienced several fires caused by a lithium battery in the course of being charged. The subsequent investigations revealed lessons for all of us.

Lithium-ion or lithium-polymer batteries are typically used in electric cars, e-bikes, computers and other power operated equipment as well as smartphones or e-cigarettes. Even when they’re small these batteries are miniature power plants.

Here are some precautions to bear in mind in order to minimise the fire risk from these batteries:

Things you should do:

  • Use according to manufacturer’s instructions

          Read and follow the manufacturer’s instructions precisely!

  • Safe batteries

          Make sure your batteries are safe: regularly check the condition (damage, deformation, leakage…) of the battery and immediately replace any damaged battery.

  • Suitable charger

          Use the charger supplied with the battery. It is designed to monitor the charge and avoid overcharging.  If the original charger is not available, you may also use a CE certified charger approved for the particular device.

  • Charging under supervision

          Supervise the charging of your batteries, in particular for powerful ones like e-bikes batteries, for example.

  • Removal of battery from device

          Where batteries are designed to be removed for charging, always remove the batteries from the device before charging.

  • Unplug

          Unplug the charger once the battery is charged.

  • Safe disposal

          When not in use leave your batteries, in particular powerful ones, in a fire-proof cupboard or bag, if possible.

          Batteries are hazardous waste that must be disposed of following the appropriate procedures:

          As batteries are never fully discharged it is recommended to seal the electrical poles with tape and/or put them in fire-proof bags prior to disposal.


Things you should avoid:

  • Charging under high temperatures

          Don’t charge a battery when the ambient temperature is above 35°.

  • Charging close to combustible materials or hazardous substances

          Do not charge batteries close to combustible materials or hazardous substances.  (chemicals, explosives….). Avoid charging underground if possible.


Immediate actions you should take in case of overheating or fire

In the event your battery is overheating, swelling, melting, emitting smoke or a clacking sound evacuate the premises, close the door, warn your colleagues and call the CERN fire brigade at 74444 or +41 22 767 4444.