askST: Why do power banks catch fire, and how do I stop it from happening?

SINGAPORE – If you like to keep your power bank in your bag while using it to charge your devices, you should stop doing so to avoid danger, say experts.

The ubiquitous portable power source, which can be bought for as little as $9, has come under scrutiny in recent months, following fires involving such devices.

One such fire in January destroyed an Air Busan plane on the tarmac in South Korea in January, after which a number of airlines banned passengers from using or keeping the power bank in overhead compartments on planes, citing safety concerns.

In March, 650 commuters had to alight at Raffles Place MRT station after a woman’s power bank caught fire in a train cabin.

Q: Why would a power bank catch fire?

A: A power bank is more prone to short circuits and fire if it has internal defects or swelling, and is exposed to changes in temperature and pressure, said Associate Professor Sivaneasan Bala Krishnan of Singapore Institute of Technology’s engineering cluster.

“Aeroplanes experience significant pressure and temperature changes, especially during take-off and landing,” he added.

He noted that power banks can also catch fire even if they are not in use.

A defective or ageing battery can break down and cause heat to build up internally, resulting in a fire, he said. A swollen battery – likely caused by a build-up of gas – can rupture and release flammable gases that ignite.

If the power bank is in a bag or pocket with metal items such as keys, coins and charging cables, the exposed USB ports could short-circuit, leading to a fire, said Prof Sivaneasan.

Q: Is my power bank in good condition?

A: Power banks that are too old or have been used a lot should be avoided, said Assistant Professor Hung Ding Nguyen of Nanyang Technological University’s School of Electrical and Electronic Engineering.

He added: “This can be identified if your power bank drains quickly or takes too long to charge.”

Other tell-tale signs include deformation, a smell, sounds such as hissing or popping, and abnormal levels of heat generation.

Power banks that have been structurally damaged after a drop, or hit with a heavy or sharp object should not be used, said Prof Nguyen.

Q: How do I use my power bank properly?

A: As power banks tend to heat up when they are being charged or used, you should use them in cool or well-ventilated areas to prevent overheating.

Avoid keeping the power bank inside your bag while it is charging your device, added Prof Nguyen. The bag will not allow the battery to cool down, which may lead to it overheating.

Heat can also build up if the device is used in spots such as under pillows and blankets, or inside a closed drawer.

Prof Sivaneasan said: “This becomes worse if it is placed next to a heat-emitting device such as a laptop or smartphone, which could further risk (overheating).”

Prof Nguyen said batteries should not be kept under direct sunlight, or used in high-humidity places such as swimming pools and bathrooms, for extended periods of time.

Q: How do I keep my power bank in good condition?

A: Unplug it after a full charge to prevent overcharging, and avoid fully using its charge, said Prof Sivaneasan. The device should be recharged when it reaches 20 to 30 per cent capacity.

Both overcharging and discharging can lead to power banks short-circuiting, he added.

Fast charging a power bank can also generate excess heat that may increase the risk of fire if the power bank is not able to dissipate heat properly, and speed up battery degradation, Prof Sivaneasan said.

You should use manufacturer-approved chargers to ensure that safe voltage and current levels run through the device.

“By following these simple safety practices, consumers can extend the lifespan of their power banks while minimising fire and explosion hazards,” he added.

Q: If I am buying a new power bank, what are some safety features I should look out for?

A: Both professors advise consumers to look out for features such as:

• Battery management system to regulate the charging and discharging process
• Overcharge protection to stop the charging process when a device is fully charged
• Thermal cut-off to stop operations when temperature exceeds a certain threshold
• Safety certifications such as ones issued by Underwriters Laboratories or International Electrotechnical Commission
• Brands that provide a warranty, and have a service centre near you

Lithium-ion type batteries are common but prone to overheating and swelling if misused, said Prof Sivaneasan. Lithium-polymer type batteries are slimmer and safer, while lithium iron phosphate types offer the best stability and lifespan, but are slightly heavier.

The Consumer Product Safety Office (CPSO) administers the regulations in Singapore, which require suppliers to ensure that general consumer goods, including power banks, follow safety standards before they can be sold.

CPSO director Beatrice Wong said in a media reply that suppliers are not required to seek pre-market approval or certification for these products.

But they must comply with safety standards for the internal components, and provide customers with information such as instructions on how to charge the power bank, and the minimum and maximum operating temperatures.

The agency conducts market surveillance, and can direct suppliers to halt sales of non-compliant power banks and notify buyers of safety risks, if the devices do not meet the requirements.

Suppliers who fail to comply with CPSO’s directions may be fined up to $10,000, jailed for up to two years, or both.

“Consumers should also be aware of potential false representation as certain power banks have been incorrectly advertised as ‘CPSO approved’ or ‘Enterprise Singapore approved’,” added Ms Wong.

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