Safety alert issued about fires on battery-powered tools

Original article published by Australian Institute of Health and Safety

The NSW Resources Regulator recently issued a safety alert following a number of incidents in which portable tools that use lithium-ion and lithium-polymer batteries caught fire.

Lithium-ion and lithium polymer batteries are the preferred energy source for portable tools due to the high levels of energy that the batteries provide.

However, this introduces the risk of fire or explosion when batteries and battery charging equipment are not used according to the manufacturer’s safety directions, and the alert said batteries can enter a state of ‘thermal runaway’ when subjected to over-charging, damage or abuse.

Abuse includes dropping, crushing, piercing, or being subjected to vibration or higher-than-normal temperatures from external heat sources.

Depending on the state of charge of the battery, thermal runaway may lead to rupturing the battery cells with subsequent fire resulting in the complete destruction of the battery, or the production of a vapour cloud with significant explosion risk and toxic gases.

With regards to the incidents, the regulator said the lithium-ion batteries:

• caught fire while being transported in a tool bag in the back of a work utility at an open-cut mine. The battery was free to move within the tool bag and was possibly short-circuited.
• caught fire while connected to a charger in an underground mine. The fault was identified as being caused by moisture ingress, which led to the thermal runaway of the battery.
• was left unattended on the back seat of a utility. The inside temperature of the vehicle exceeded the maximum recommended temperature for the battery and resulted in the battery catching fire.
• caught fire when run over after falling out of a man basket in an underground mine.

The regulator subsequently made a number of recommendations:

• Only use charging equipment recommended by the manufacturer for that particular battery.
• Ensure that transporting of spare batteries does not expose them to the risk of physical damage or short circuit of the connecting pins.
• Do not expose batteries to water as this can cause a short circuit between the battery connections.
• Do not expose batteries to temperatures greater than 50 degrees celsius, or as recommended by the manufacturer. It should be noted that temperatures inside a vehicle can be much greater than external ambient temperatures. For example, the internal temperature of a vehicle left with windows up with an ambient temperature of 35 degrees celsius can reach 60 degrees celsius in 60 minutes. The temperature in an open-cut mine in full sun can be up to 10 degrees celsius higher than surface temperatures.

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